DPA425P-TL - Power Integrations, Inc.

Figure 1. Typical Forward Converter Application.

Table 1. Notes: 1. Maximum output power is limited by device internal

current limit. 2. See Applications Considerations section for complete

description of assumptions and for output powers with other input voltage

ranges. 3. For device dissipation of 1.5 W or below, use P or G packages.

Device dissipation above 1.5 W is possible only with R package. 4. See

Part Ordering Information. 5. Due to higher switching losses, the DPA425

may not deliver additional power compared to a smaller device.

DPA423-426

DPA-Switch

Family

Highly Integrated DC-DC Converter ICs

for Distributed Power Architectures

The following transparent or built-in features are also provided:

soft-start, cycle skipping down to zero load and hysteretic

thermal shutdown. In addition, all critical parameters (i.e.

current limit, frequency, PWM gain) have tight temperature

and absolute tolerance, to simplify design and optimize system

cost.

Product Highlights

Highly Integrated Solution

• Eliminates 20-50 external components–saves space, cost

•Integrates 220 V high frequency MOSFET, PWM control

•Lower cost plastic DIP surface mount (G package) and

through-hole (P package) options for designs ≤35 W

Superior Performance and Flexibility

•Eliminates all external current sensing circuitry

•Built-in auto-restart for output overload/open loop protection

•Pin selectable 300/400 kHz fixed frequency

•Wide input (line) voltage range: 16-75 VDC

•Source connected tab reduces EMI

•Line under-voltage (UV) detection: meets ETSI standards

•Line overvoltage (OV) shutdown protection

•Low cost synchronous rectification: line UV/OV shut down

limits gate drive voltage range from transformer winding

•Fully integrated soft-start for minimum stress/overshoot

•Externally programmable current limit

•Supports forward or flyback topology

•Cycle skipping: regulation to zero load without pre-load

•Hysteretic thermal shutdown for automatic fault recovery

EcoSmart

Energy Efficient

• Extremely low consumption at no load

•Cycle skipping at light load for high standby efficiency

Applications

•Telco central office equipment: xDSL, ISDN, PABX, etc.

•Distributed power architectures (24 V/48 V bus, etc.)

•Digital feature phones, VoIP phones, PoE

•Industrial controls (24 V/48 V)

Description

The DPA-Switch IC family introduces a highly integrated

solution for DC-DC conversion applications in the 16-75 VDC

input range.

DPA-Switch uses the same proven topology as TOPSwitch, cost

effectively integrating the high voltage power MOSFET, PWM

control, fault protection and other control circuitry onto a single

CMOS chip. High performance features are enabled with three

user configurable pins.

January 2004

PRODUCT4

OUTPUT POWER TABLE

12 W 16 W - - - 18 W

16 W 23 W 35 W - - 35 W

23 W 32 W 50 W 62 W - 70 W

25 W 35 W 55 W 70 W 83 W 100 W

DPA423

DPA424

DPA425

DPA426

36-75 VDC INPUT RANGE (FORWARD)2,4

Total Device

Dissipation30.5 W 1 W 2.5 W 4 W 6 W Max

Power

Output1

PI-2770-032002

DPA-Switch

VIN

CONTROL

SENSE

CIRCUIT

RESET/

CLAMP

CIRCUIT

™

PRODUCT4

9 W 13 W - - 13 W

10 W 14.5 W 18 W 24 W 26 W

-5-5-525.5 W 52 W

DPA423

DPA424

DPA425

36-75 VDC INPUT RANGE (FLYBACK)2

Total Device3

Dissipation 0.5 W 0.75 W 1 W 1.5 W Max

Power

Output1

DPA423-426

1/04

Section List

Functional Block Diagram......................................................................................................................................... 3

Pin Functional Description........................................................................................................................................ 3

DPA-Switch

Family Functional Description..............................................................................................................4

CONTROL (C) Pin Operation .................................................................................................................................4

Oscillator and Switching Frequency .......................................................................................................................5

Pulse Width Modulator & Maximum Duty Cycle .....................................................................................................6

Minimum Duty Cycle and Cycle Skipping...............................................................................................................6

Error Amplifier.........................................................................................................................................................6

On-chip Current Limit with External Programmability.............................................................................................6

Line Under-Voltage Detection (UV) ........................................................................................................................6

Line Overvoltage Shutdown (OV)...........................................................................................................................7

Line Feed Forward with DCMAX Reduction ..............................................................................................................7

Remote ON/OFF ....................................................................................................................................................7

Synchronization ......................................................................................................................................................8

Soft-Start ................................................................................................................................................................8

Shutdown/Auto-Restart ..........................................................................................................................................8

Hysteretic Over-Temperature Protection ................................................................................................................8

Bandgap Reference................................................................................................................................................8

High-Voltage Bias Current Source..........................................................................................................................8

Using Feature Pins......................................................................................................................................................9

FREQUENCY (F) Pin Operation.............................................................................................................................9

LINE-SENSE (L) Pin Operation..............................................................................................................................9

EXTERNAL CURRENT LIMIT (X) Pin Operation ...................................................................................................9

Typical Uses of FREQUENCY (F) Pin ......................................................................................................................12

Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins.......................................................12

Application Examples...............................................................................................................................................15

Key Application Considerations ..............................................................................................................................17

DPA-Switch

Design Considerations......................................................................................................................17

DPA-Switch

Layout Considerations ......................................................................................................................18

Quick Design Checklist.........................................................................................................................................19

Design Tools .........................................................................................................................................................19

Product Specifications and Test Conditions ..........................................................................................................21

Typical Performance Characteristics ..................................................................................................................... 27

Part Ordering Information ........................................................................................................................................31

Package Outlines ......................................................................................................................................................32

DPA423-426

1/04

Figure 2. Functional Block Diagram.

PI-2760-070501

SHUTDOWN/

AUTO-RESTART

PWM

COMPARATOR

CLOCK

SAW

300/400 kHz

CONTROLLED

TURN-ON

GATE DRIVER

CURRENT LIMIT

COMPARATOR

INTERNAL UV

COMPARATOR

INTERNAL

SUPPLY

5.8 V

4.8 V

SOURCE (S)

DMAX

STOP SOFT-

START

CONTROL (C)

LINE-SENSE (L)

EXTERNAL

CURRENT LIMIT (X)

FREQUENCY (F)

5.8 V

1 V

IFB

LEADING

EDGE

BLANKING

÷ 8

HYSTERETIC

THERMAL

SHUTDOWN

SHUNT REGULATOR/

ERROR AMPLIFIER +

DRAIN (D)

ON/OFF

SOFT

START

DCMAX

VBG

DCMAX

VBG + VT

OV/UV

I (LIMIT)

CURRENT

LIMIT

ADJUST

LINE

SENSE

SOFT START

CYCLE

SKIPPING

STOP LOGIC

OSCILLATOR

Figure 3. Pin Configuration (top view).

Pin Functional Description

DRAIN (D) Pin:

High voltage power MOSFET drain output. The internal startup

bias current is drawn from this pin through a switched high-

voltage current source. Internal current limit sense point for

drain current.

CONTROL (C) Pin:

Error amplifier and feedback current input pin for duty cycle

control. Internal shunt regulator connection to provide internal

bias current during normal operation. It is also used as the

connection point for the supply bypass and auto-restart/

compensation capacitor.

LINE-SENSE (L) Pin:

Input pin for overvoltage (OV), under-voltage (UV) lock out,

line feed forward with the maximum duty cycle (DCMAX)

reduction, remote ON/OFF and synchronization. A connection

to SOURCE pin disables all functions on this pin.

EXTERNAL CURRENT LIMIT (X) Pin:

Input pin for external current limit adjustment and remote

ON/OFF. A connection to SOURCE pin disables all functions

on this pin.

PI-3822-012104

Tab Internally Connected to

SOURCE Pin (See layout considerations)

R Package

(TO-263-7C)

12345 7

CLXSF D

P Package (DIP-8)

G Package (SMD-8)

FREQUENCY (F) Pin:

Input pin for selecting switching frequency: 400 kHz if connected

to SOURCE pin and 300 kHz if connected to CONTROL pin.

SOURCE (S) Pin:

Output MOSFET source connection for the power return.

Primary side control circuit common and reference point.

DPA423-426

1/04

Figure 4. Relationship of Duty Cycle to CONTROL Pin Current.

DPA-Switch

Family Functional

Description

DPA-Switch is an integrated switched mode power supply chip

that converts a current at the control input to a duty cycle at the

open drain output of a high voltage power MOSFET. During

normal operation the duty cycle of the power MOSFET decreases

linearly with increasing CONTROL pin current as shown in

Figure 4. A patented high-voltage CMOS technology allows

both the high-voltage power MOSFET and all the low voltage

control circuitry to be cost effectively integrated onto a single

monolithic chip.

In addition to the standard TOPSwitch features, such as the

high-voltage start-up, the cycle-by-cycle current limiting, loop

compensation circuitry, auto-restart and thermal shutdown,

DPA-Switch also offers many advanced features that reduce

system cost and increase power supply performance and design

flexibility. Following is a summary of the advanced features:

1. A fully integrated 5 ms soft-start limits peak currents and

voltages during start-up and reduces or eliminates output

overshoot in most applications.

2. A 75% maximum duty cycle (DCMAX) together with the

line feed forward with DCMAX reduction feature makes

DPA-Switch well suited for both flyback and forward

topologies.

3. High switching frequency (400 kHz/300 kHz, pin selectable)

allows the use of smaller size transformers and offers high

bandwidth for power supply control loop.

4. Cycle skipping operation at light load minimizes standby

power consumption (typically <10 mA input current).

5. Line under-voltage ensures glitch free operations at both

power-up and power-down and is tightly toleranced over

process and temperature to meet system level requirements

common in DC to DC converters (e.g. ETSI).

6. Line overvoltage protects DPA-Switch against excessive

input voltage and line surge.

7. External current limit adjustment allows the setting of the

current limit externally to a lower level near the operating

peak current and, if desired, further adjusts the level

gradually as line voltage rises. This makes possible an ideal

implementation of overload power limiting.

8. Synchronization function allows the synchronization of

DPA-Switch operation to an external lower frequency.

9. Remote ON/OFF feature permits DPA-Switch based power

supplies to be easily switched on/off using logic signals.

Maximum input current consumption is 2 mA in Remote

OFF.

10. Hysteretic over-temperature shutdown provides automatic

recovery from thermal fault.

11. Tight absolute tolerances and small temperature variations

on switching frequency, current limit, and under-voltage

lock out threshold (UV).

Three pins, LINE-SENSE (L), EXTERNAL CURRENT LIMIT

(X) and FREQUENCY (F), are used to implement all the pin

controllable features. A resistor from the LINE-SENSE pin to

DC input bus implements line UV, line OV and line feed

forward with DCMAX reduction. A resistor from the EXTERNAL

CURRENT LIMIT pin to the SOURCE pin sets current limit

externally. In addition, remote ON/OFF may be implemented

through either the LINE-SENSE pin or the EXTERNAL

CURRENT LIMIT pin depending on the polarity of the logic

signal available as well as other system specific considerations.

Shorting both the LINE-SENSE and the EXTERNAL

CURRENT LIMIT pins to the SOURCE pin disables line OV,

line UV, line feed forward with DCMAX reduction, external

current limit, remote ON/OFF and synchronization. The

FREQUENCY pin sets the switching frequency to 400 kHz if

connected to the SOURCE pin, or 300 kHz if connected to the

CONTROL pin. This pin should not be left open. Please refer

to “Using Feature Pins” section for detailed information

regarding the proper use of those pins.

CONTROL Pin Operation

The CONTROL pin is a low impedance node that is capable of

receiving a combined supply and feedback current. During

normal operation, a shunt regulator is used to separate the

feedback signal from the supply current. CONTROL pin

voltage VC is the supply voltage for the control circuitry

including the MOSFET gate driver. An external bypass capacitor

closely connected between the CONTROL and SOURCE pins

is required to supply the instantaneous gate drive current. The

total amount of capacitance connected to this pin also sets the

auto-restart timing as well as control loop compensation.

When the DC input voltage is applied to the DRAIN pin during

start-up, the MOSFET is initially off, and the CONTROL pin

capacitor is charged through the switched high voltage current

source connected internally between the DRAIN and

CONTROL pins. When the CONTROL pin voltage VC reaches

PI-2761-112102

Duty Cycle (%)

(mA)

= 115 µA

L(DC)

(SKIP)

Slope = PWM Gain

CD1

Auto-restart

DPA423-426

1/04

approximately 5.8 V, the control circuitry is activated and the

soft-start begins. The soft-start circuit gradually increases the

duty cycle of the MOSFET from zero to the maximum value

over approximately 5 ms. The high voltage current source is

turned off at the end of the soft-start. If no external feedback/

supply current is fed into the CONTROL pin by the end of the

soft-start, the CONTROL pin will start discharging in response

to the supply current drawn by the control circuitry and the gate

current of the switching MOSFET driver. If the power supply

is designed properly, and no fault condition such as open loop

or overloaded output exists, the feedback loop will close,

providing external CONTROL pin current, before the

CONTROL pin voltage has had a chance to discharge to the

lower threshold voltage of approximately 4.8 V (internal supply

under-voltage lockout threshold). When the externally fed

current charges the CONTROL pin to the shunt regulator

voltage of 5.8 V, current in excess of the consumption of the

chip is shunted to SOURCE through resistor RE as shown in

Figure 2. This current flowing through RE controls the duty

cycle of the power MOSFET to provide closed loop regulation.

The shunt regulator has a finite low output impedance ZC that

sets the gain of the error amplifier when used in a primary

feedback configuration. The dynamic impedance ZC of the

CONTROL pin together with the external CONTROL pin

capacitance sets the dominant pole for the control loop.

When a fault condition such as an open loop or overloaded

output prevents the flow of an external current into the

CONTROL pin, the capacitor on the CONTROL pin discharges

towards 4.8 V. At 4.8 V auto-restart is activated which turns the

output MOSFET off and puts the control circuitry in a low

PI-2545-050602

S1 S2 S6 S7 S1 S2 S6 S7S0 S1 S7

S0 S0

5.8 V

4.8 V

0 V

VLINE

VDRAIN

VOUT

Note: S0 through S7 are the output states of the auto-restart counter

1234

0 V

S6 S7

VUV

Figure 5. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down.

current standby mode. The high-voltage current source turns on

and charges the external capacitance again. A hysteretic

internal supply under-voltage comparator keeps VC within a

window of typically 4.8 to 5.8 V by turning the high-voltage

current source on and off as shown in Figure 5. The auto-restart

circuit has a divide-by-8 counter that prevents the output

MOSFET from turning on again until eight discharge/charge

cycles have elapsed. This is accomplished by enabling the

output MOSFET only when the divide-by-8 counter reaches

full count (S7). The counter effectively limits DPA-Switch

power dissipation as well as the maximum power delivered to

the power supply output by reducing the auto-restart duty cycle

to typically 4%. Auto-restart mode continues until output

voltage regulation is again achieved through closure of the

feedback loop.

Oscillator and Switching Frequency

The internal oscillator linearly charges and discharges an internal

capacitance between two voltage levels to create a sawtooth

waveform for the pulse width modulator. The oscillator sets

both the pulse width modulator latch and the current limit latch

at the beginning of each cycle.

The nominal switching frequency of 400 kHz was chosen to

minimize the transformer size and to allow faster power supply

loop response. The FREQUENCY pin, when shorted to the

CONTROL pin, lowers the switching frequency to 300 kHz,

which may be preferable in some applications such as those

employing secondary synchronous rectification. Otherwise,

the FREQUENCY pin should be connected to the SOURCE pin

for the default 400 kHz.

DPA423-426

1/04

Pulse Width Modulator and Maximum Duty Cycle

The pulse width modulator implements voltage mode control

by driving the output MOSFET with a duty cycle inversely

proportional to the current into the CONTROL pin that is in

excess of the internal supply current of the chip (see Figure 4).

The excess current is the feedback error signal that appears

across RE (see Figure 2). This signal is filtered by an RC network

with a typical corner frequency of 30 kHz to reduce the effect

of switching noise in the chip supply current generated by the

MOSFET gate driver. The filtered error signal is compared with

the internal oscillator sawtooth waveform to generate the duty

cycle waveform. As the control current increases, the duty cycle

decreases. A clock signal from the oscillator sets a latch that

turns on the output MOSFET. The pulse width modulator resets

the latch, turning off the output MOSFET. Note that a minimum

current must be driven into the CONTROL pin before the duty

cycle begins to change.

The maximum duty cycle, DCMAX is set at a default maximum

value of 75% (typical). However, by connecting the

LINE-SENSE to the DC input bus through a resistor with

appropriate value, the maximum duty cycle can be made to

decrease from 75% to 33% (typical) as shown in

Figure 7 when input line voltage increases (see line feed

forward with DCMAX reduction).

Minimum Duty Cycle and Cycle Skipping

To maintain power supply output regulation, the pulse width

modulator reduces duty cycle as the load at the power supply

output decreases. This reduction in duty cycle is proportional to

the current flowing into the CONTROL pin. As the CONTROL

pin current increases, the duty cycle reduces linearly towards a

minimum value specified as minimum duty cycle, DCMIN. After

reaching DCMIN, if CONTROL pin current is increased further

by approximately 2 mA, the pulse width modulator will force

the duty cycle from DCMIN to zero in a discrete step (refer to

Figure 4). This feature allows a power supply to operate in a

cycle skipping mode when the load consumes less power than

the DPA-Switch delivers at minimum duty cycle, DCMIN. No

additional control is needed for the transition between normal

operation and cycle skipping. As the load increases or decreases,

the power supply automatically switches between normal and

cycle skipping mode as necessary.

Cycle skipping may be avoided, if so desired, by connecting a

minimum load at the power supply output such that the duty

cycle remains at a level higher than DCMIN at all times.

Error Amplifier

The shunt regulator can also perform the function of an error

amplifier in primary side feedback applications. The shunt

regulator voltage is accurately derived from a temperature-

compensated bandgap reference. The gain of the error amplifier

is set by the CONTROL pin dynamic impedance. The

CONTROL pin clamps external circuit signals to the VC voltage

level. The CONTROL pin current in excess of the supply

current is separated by the shunt regulator and flows through RE

as a voltage error signal.

On-chip Current Limit with External Programmability

The cycle-by-cycle peak drain current limit circuit uses the

output MOSFET ON-resistance as a sense resistor. A current

limit comparator compares the output MOSFET on-state drain

to source voltage, VDS(ON) with a threshold voltage. At the

current limit, VDS(ON) exceeds the threshold voltage and the

MOSFET is turned off until the start of the next clock cycle. The

current limit comparator threshold voltage is temperature

compensated to minimize the variation of the current limit due

to temperature related changes in RDS(ON) of the output MOSFET.

The default current limit of DPA-Switch is preset internally.

However, with a resistor connected between EXTERNAL

CURRENT LIMIT pin and SOURCE pin, the current limit can

be programmed externally to a lower level between 25% and

100% of the default current limit. Please refer to the graphs in

the Typical Performance Characteristics section for the

selection of the resistor value. By setting current limit low, a

larger DPA-Switch than necessary for the power required can be

used to take advantage of the lower RDS(ON) for higher efficiency/

smaller heat sinking requirements. With a second resistor

connected between the EXTERNAL CURRENT LIMIT pin

and the DC input bus, the current limit is reduced with increasing

line voltage, allowing a true power limiting operation against

line variation to be implemented in a flyback configuration.

The leading edge blanking circuit inhibits the current limit

comparator for a short time after the output MOSFET is turned

on. The leading edge blanking time has been set so that, if a

power supply is designed properly, current spikes caused by

primary-side capacitance and secondary-side rectifier reverse

recovery time should not cause premature termination of the

switching pulse.

The current limit after the leading edge blanking time is as

shown in Figure 31. To avoid triggering the current limit in

normal operation, the drain current waveform should stay

within the envelope shown.

Line Under-Voltage Detection (UV)

At power up, UV keeps DPA-Switch off until the input line

voltage reaches the under voltage upper threshold. At power

down, UV holds DPA-Switch on until the input voltage falls

below the under voltage lower threshold. A single resistor

connected from the LINE-SENSE pin to the DC input bus sets

UV upper and lower thresholds. To avoid false triggering by

noise, a hysteresis is implemented which sets the UV lower

threshold typically at 94% of the UV upper threshold. If the UV

lower threshold is reached during operation without the power

supply losing regulation and the condition stays longer than

10 µs (typical), the device will turn off and stay off until the UV

upper threshold has been reached again. Then, a soft-start

DPA423-426

1/04

will be initiated the next time CONTROL pin voltage reaches

5.8.V. If the power supply loses regulation before reaching the

UV lower threshold, the device will enter auto-restart. At the

end of each auto-restart cycle (S7), the UV comparator is

enabled. If the UV upper threshold is not exceeded the MOSFET

will be disabled during the next cycle (see Figure 5). The UV

feature can be disabled independent of OV feature.

Line Overvoltage Shutdown (OV)

The same resistor used for UV also sets an over voltage

threshold which, once exceeded, will force the DPA-Switch

output into the off-state within one switching cycle. The ratio of

OV and UV thresholds is preset at 2.7 as can be seen in

Figure 7. When the MOSFET is off, the input voltage surge

capability is increased to the voltage rating of the MOSFET

(220 V), due to the absence of the reflected voltage and leakage

spikes on the drain. A small amount of hysteresis is provided on

the OV threshold to prevent noise triggering. The OV feature

can be disabled independent of the UV feature as shown in

Figure 13.

Line Feed Forward with DCMAX Reduction

The same resistor used for UV and OV also implements line

voltage feed forward that minimizes output line ripple and

reduces power supply output sensitivity to line transients. This

feed forward operation is illustrated in Figure 4 by the different

values of IL. Note that for the same CONTROL pin current,

higher line voltage results in smaller operating duty cycle. As

an added feature, the maximum duty cycle DCMAX is also

reduced from 75% (typical) at a voltage slightly higher than the

UV threshold to 33% (typical) at the OV threshold

(see Figures 4, 7). Limiting DCMAX at higher line voltages helps

prevent transformer saturation due to large load transients in

forward converter applications. DCMAX of 33% at the OV

threshold was chosen to ensure that the power capability of the

DPA-Switch is not restricted by this feature under normal

operation.

Remote ON/OFF

Remote ON/OFF control describes operation where the IC is

turned on or off for long periods as opposed to the cycle-by-

cycle on/off control which is described in the Synchronization

section below.

DPA-Switch can be turned on or off by controlling the current

into the LINE-SENSE pin or out from the EXTERNAL

CURRENT LIMIT pin (see Figure 7). This allows easy

implementation of remote ON/OFF control of DPA-Switch in

several different ways. A transistor or an optocoupler output

connected between the EXTERNAL CURRENT LIMIT pin

and the SOURCE pin implements this function with “active-

on” (Figures 17, 19 and 21) while a transistor or an optocoupler

output connected between the LINE-SENSE pin and the

CONTROL pin implements the function with “active-off”

(Figures 18, 20 and 22).

When a signal is received at the LINE-SENSE pin or the

EXTERNAL CURRENT LIMIT pin to disable the output

through any of the pin functions such as OV, UV and remote

ON/OFF, DPA-Switch always completes its current switching

cycle before the output is forced off. The internal oscillator is

stopped at the end of the current cycle and stays there as long as

the disable signal exists. When the signal at the above pins

changes state from disable to enable, the internal oscillator

starts the next switching cycle.

The remote ON/OFF feature can be used as a standby or power

switch to turn off the DPA-Switch and keep it in a very low

power consumption state for indefinitely long periods. If the

DPA-Switch is held in remote-off state for longer than 10 µs

Figure 6. Synchronization Timing Diagram.

PI-2762-070501

Oscillator

(SAW)

MAX

2 V

0 V

SYNC

≥ 128 kHz; t

OFF

≤ 7.7 µs; 120 ns ≤ t

≤ 2250 ns for f

OSC

= 400 kHz

≤ 3080 ns for f

OSC

= 300 kHz

OFF

ON OFF SYNC

Time

DPA423-426

1/04

(typical), the CONTROL pin goes into the hysteretic mode of

operation. In this mode, the CONTROL pin goes through

alternate charge and discharge cycles between 4.8 V and 5.8 V

(see CONTROL Pin Operation section above) and the IC runs

entirely off the high voltage DC input, but with very low power

consumption (30 mW typical at 48 V with LINE-SENSE and

EXTERNAL CURRENT LIMIT pins open). When the

DPA-Switch is remotely turned on after entering this mode, it

will initiate a normal start-up sequence with soft-start the next

time the CONTROL pin reaches 5.8 V. In the worst case, the

delay from remote on to start-up can be equal to the full

discharge/charge cycle time of the CONTROL pin, which is

approximately 36 ms for a 22 µF CONTROL pin capacitor.

This reduced-consumption remote-off mode can eliminate

expensive and unreliable in-line mechanical switches. It also

allows for microprocessor-controlled turn-on and turn-off

sequences that may be required in certain applications.

Synchronization

In addition to sensing incoming current for OV, UV and remote

ON/OFF, the LINE-SENSE pin also monitors its pin voltage

through a 1 V threshold comparator. A pin voltage below 1 V

turns on DPA-Switch. When the voltage at LINE-SENSE pin

rises beyond 1 V to disable the output, DPA-Switch completes

its current switching cycle before the output is forced off

(similar to remote ON/OFF operation). The internal oscillator

is stopped at the end of the current cycle awaiting the

LINE-SENSE pin voltage to go low to start the next cycle. This

allows the use of the 1 V threshold to synchronize DPA-Switch

to an external signal with a frequency lower than its internal

switching frequency. A transistor or an optocoupler output

connected between the LINE-SENSE pin and the SOURCE pin

implements this function (see Figure 24). Please refer to

Figure 6 for the timing waveforms of synchronization operation.

In order to be recognized as a synchronization pulse, the

LINE-SENSE pin needs to stay low (on-time) for at least

120 ns but no more than 2250 ns for 400 kHz (or 3080 ns for

300 kHz) internal switching frequency. In addition, the off-time

must be kept below 7.7 µs which is a limitation set by the lowest

synchronization frequency of 128 kHz allowed by the chip. The

effective DCMAX for synchronization operation can be calculated

as 0.75 x fSYNC/fOSC. An off-time longer than 7.7 µs may force the

CONTROL pin to go into the hysteretic mode and initiate a soft-

start cycle at next turn-on.

Soft-Start

Two on-chip soft-start functions are activated at start-up with a

duration of 5 ms (typical). Maximum duty cycle starts from 0%

and linearly increases to the default maximum of 75% at the end

of the 5 ms duration and the current limit starts from about 85%

and linearly increases to 100% at the end of the 5 ms duration.

In addition to start-up, soft-start is also activated at each restart

attempt during auto-restart and when restarting after being in

hysteretic regulation of CONTROL pin voltage (VC), due to

remote off or thermal shutdown conditions. This effectively

minimizes current and voltage stresses on the output MOSFET,

the clamp circuit and the output rectifier during start-up. This

feature also helps minimize output overshoot and prevents

saturation of the transformer during start-up.

Shutdown/Auto-Restart

To minimize DPA-Switch power dissipation under fault

conditions, the shutdown/auto-restart circuit turns the power

supply on and off at an auto-restart duty cycle of typically 4%

if an out of regulation condition persists. Loss of regulation

interrupts the external current into the CONTROL pin. VC

regulation changes from shunt mode to the hysteretic auto-

restart mode as described in CONTROL pin operation section.

When the fault condition is removed, the power supply output

becomes regulated, VC regulation returns to shunt mode, and

normal operation of the power supply resumes.

Hysteretic Over-Temperature Protection

Over temperature protection is provided by a precision analog

circuit that turns the output MOSFET off when the junction

temperature exceeds the thermal shutdown temperature

(137 °C typical). When the junction temperature cools to below

the hysteretic temperature (110 °C typical), normal operation

resumes providing automatic recovery. VC is regulated in

hysteretic mode and a 4.8 V to 5.8 V (typical) sawtooth

waveform is present on the CONTROL pin while in thermal

shutdown.

Bandgap Reference

All critical DPA-Switch internal voltages are derived from a

temperature-compensated bandgap reference. This reference is

also used to generate a temperature-compensated current

reference that is trimmed to accurately set the switching

frequency, current limit, and the line OV/UV thresholds.

DPA-Switch has improved circuitry to maintain all of the above

critical parameters within very tight absolute and temperature

tolerances.

High-Voltage Bias Current Source

This current source biases DPA-Switch from the DRAIN pin

and charges the CONTROL pin external capacitance during

start-up or hysteretic operation. Hysteretic operation occurs

during auto-restart, remote off and over-temperature shutdown.

In this mode of operation, the current source is switched on and

off with an effective duty cycle of approximately 20%. This

duty cycle is determined by the ratio of CONTROL pin charge

(IC(CH)) and discharge currents (ICD1 and ICD2). This current

source is turned off during normal operation when the output

MOSFET is switching. The effect of the current source switching

may be seen on the DRAIN voltage waveform as small

disturbances which is normal.

DPA423-426

1/04

Using Feature Pins

FREQUENCY (F) Pin Operation

The FREQUENCY pin is a digital input pin. Shorting the

FREQUENCY pin to SOURCE pin selects the nominal

switching frequency of 400 kHz (Figure 9) which is suited for

most applications. For other applications that may benefit from

lower switching frequency, a 300 kHz switching frequency can

be selected by shorting the FREQUENCY pin to the CONTROL

pin (Figure 10). This pin should not be left open.

LINE-SENSE (L) Pin Operation

When current is fed into the LINE-SENSE pin, it works as a

voltage source of approximately 2.6 V up to a maximum current

of +240 µA (typical). At +240 µA, this pin turns into a constant

current sink. Refer to Figure 8. In addition, a comparator with

a threshold of 1 V is connected at the pin and is used to detect

when the pin is shorted to the SOURCE pin.

There are a total of five functions available through the use of

the LINE-SENSE pin: OV, UV, line feed forward with DCMAX

reduction, remote ON/OFF and synchronization. Shorting the

LINE-SENSE pin to the SOURCE pin disables all five functions.

The LINE-SENSE pin is typically used for line sensing by

connecting a resistor from this pin to the positive input DC

voltage bus to implement OV, UV and line feed forward with

DCMAX reduction over line voltage. In this mode, the value of the

resistor determines the line OV/UV thresholds, and the DCMAX

is reduced linearly with input DC high voltage starting from just

above the UV threshold. This pin can also be used as the input

pin for remote ON/OFF and synchronization. An external

transistor placed between the LINE-SENSE pin and the

CONTROL pin realizes remote on/off via UV or OV threshold.

Synchronization is available by connecting an open drain

external MOSFET between the LINE-SENSE pin and the

SOURCE pin to generate synchronization pulse. Each time the

MOSFET turns on, the falling edge of the LINE-SENSE pin

voltage initiates a new switching cycle. The lowest

synchronization frequency guaranteed by DPA-Switch is

128 kHz. Refer to Table 2 for possible combinations of the

functions with example circuits shown in Figure 11 through

Figure 24. A description of specific functions in terms of the

LINE-SENSE pin I/V characteristic is shown in Figure 7 (right

hand side). The horizontal axis represents LINE-SENSE pin

current with positive polarity indicating currents flowing into

the pin. The meaning of the vertical axes varies with functions.

For those that control the on/off states of the output such as UV,

OV and remote ON/OFF, the vertical axis represents the enable/

disable states of the output. UV triggers at IUV (+50 µA typical

with 4 µA hysteresis) and OV triggers at IOV (+135 µA typical

with 4 µA hysteresis). Between the UV and OV thresholds, the

output is enabled. For line feed forward with DCMAX reduction,

the vertical axis represents the magnitude of the DCMAX Line feed

forward with DCMAX reduction lowers maximum duty cycle from

75% at IL(DC) (+55 µA typical) to 33% at IOV (+135 µA).

EXTERNAL CURRENT LIMIT (X) Pin Operation

When current is drawn out of the EXTERNAL CURRENT

LIMIT pin, it works as a voltage source of approximately 1.3 V

up to a maximum current of -230 µA (typical). At -230 µA, it

turns into a constant current source (refer to Figure 8).

There are two functions available through the use of the

EXTERNAL CURRENT LIMIT pin: external current limit and

remote ON/OFF. Shorting the EXTERNAL CURRENT LIMIT

pin and SOURCE pin disables both functions. In high efficiency

applications, this pin can be used to reduce the current limit

externally to a value close to the operating peak current, by

connecting the pin to the SOURCE pin through a resistor. The

pin can also be used as a remote on/off control input. Table 2

✔

✔✔ ✔✔✔

✔✔✔✔

✔

✔✔ ✔✔✔ ✔

✔✔✔✔✔✔

✔

11 12 13 14 15 16 17 18 19 20 21 22 23 24

Table 2. Typical LINE-SENSE and EXTERNAL CURRENT LIMIT Pin Configurations.

LINE-SENSE AND EXTERNAL CURRENT LIMIT PIN TABLE*

*This table is only a partial list of many LINE-SENSE and EXTERNAL CURRENT LIMIT pin configurations that are possible.

▲

Figure Number

Three Terminal Operation

Under-Voltage

Overvoltage

Line Feed Forward (DCMAX)

Overload Power Limiting

External Current Limit

Remote ON/OFF

Synchronization

DPA423-426

1/04

Figure 7. LINE-SENSE and EXTERNAL CURRENT LIMIT Pin Characteristics.

-250 -200 -150 -100 -50 50 100 150 200 2500 0

PI-2778-080801

Output

MOSFET

Switching

(Enabled)

(Disabled)

(Enabled)

(Disabled)

LIMIT

(Default)

Current

Limit

-21.5 µA

-25.5 µAV

+ V

UV(U)

REM(U)

OV(U)

X Pin Voltage

Output

MOSFET

Switching

Maximum

Duty Cycle

L Pin Voltage

MAX

(75%)

Note: These figures provide idealized functional characteristics with typical performance values. Please refer to the

parametric table and typical performance characteristics sections of the data sheet for measured data.

X Pin Current (µA) L Pin Current (µA)

131 µA

135 µA

47 µA

shows several different ways of using this pin. See Figure 7 for

a description of the functions where the horizontal axis (left

hand side) represents the EXTERNAL CURRENT LIMIT pin

current. The meaning of the vertical axes varies with function.

For those that control the on/off states of the output such as

remote ON/OFF, the vertical axis represents the enable/disable

states of the output. For external current limit, the vertical axis

represents the magnitude of the ILIMIT. Please see graphs in the

Typical Performance Characteristics section for the current

limit programming range and the selection of the appropriate

resistor value.

DPA423-426

1/04

Figure 8. LINE-SENSE (L), and EXTERNAL CURRENT LIMIT (X) Pin Input Simplified Schematic.

+ V

1 V

230 µA

240 µA

CONTROL Pin

(Voltage Sense)

(Positive Current Sense - Under-Voltage,

Overvoltage, ON/OFF Maximum Duty

Cycle Reduction)

(Negative Current Sense - ON/OFF,

Current Limit Adjustment)

PI-2765-080801

DPA-Switch

LINE-SENSE (L)

EXTERNAL CURRENT LIMIT (X)

DPA423-426

1/04

Figure 9. 400 kHz Frequency Operation. Figure 10. 300 kHz Frequency Operation.

Typical Uses of FREQUENCY (F) Pin

PI-2654-071700

Input

Voltage

CONTROL

PI-2655-071700

Input

Voltage

CONTROL

Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins

PI-2766-070901

Input

Voltage

CONTROL

LCS D

CLXS F D

Figure 11. Three Terminal Operation (LINE-SENSE and

EXTERNAL CURRENT LIMIT Features Disabled.

FREQUENCY Pin can be tied to SOURCE or

CONTROL Pin).

Figure 12. Line-Sensing for Under-Voltage, Overvoltage and

Line Feed Forward.

Figure 13. Line-Sensing for Under-Voltage Only (Overvoltage

Disabled). Figure 14. Line-Sensing for Overvoltage Only (Under-Voltage

Disabled). Maximum Duty Cycle will be reduced at

Low Line.

PI-2767-091302

Input

Voltage

CONTROL

619 kΩ

VUV = IUV x RLS + VL (IL = IUV)

VOV = IOV x RLS + VL (IL = IOV)

For RLS = 619 kΩ

VUV = 33.3 V

VOV = 86.0 V

PI-2852-091302

Input

Voltage

= R

x I

L (I

= I

)

For Values Shown

= 33.3 V

6.2 V

576 kΩ

42.2 kΩ

CONTROL

PI-2853-091302

Input

Voltage

CONTROL

1N4148

= I

L (I

= I

)

For Values Shown

= 86.2 V

590 kΩ

30 kΩ

DPA423-426

1/04

Figure 15. Externally Set Current Limit. Figure 16. Current Limit Reduction with Line Voltage.

PI-2836-011904

Input

Voltage

For R

= 12 kΩ

LIMIT

= 64%

See Figure 34 for other

resistor values (R

)

For R

= 25 kΩ

LIMIT

= 34%

CONTROL

PI-2854-050602

Input

Voltage

363 kΩ

RLS

4.2 kΩ

RIL

100% @ 36 VDC

64% @ 72 VDC

ILIMIT =

CONTROL

Figure 17. Active-on (Fail Safe) Remote ON/OFF. Figure 18. Active-off Remote ON/OFF. Maximum Duty Cycle will

be reduced.

Figure 19. Active-on Remote ON/OFF with Externally Set Current

Limit. Figure 20. Active-off Remote ON/OFF with Externally Set Current

Limit.

ON/OFF

47 kΩ

PI-2856-072602

Input

Voltage

For R

= 12 kΩ

LIMIT

= 64%

For R

= 25 kΩ

LIMIT

= 34%

can be an optocoupler

output or can be replaced

by a MOSFET or manual

switch.

CONTROL

PI-2857-050602

Input

Voltage

CONTROL

47 kΩ

37.4 kΩ

QR can be an

optocoupler output

or can be replaced

by a manual switch.

ON/OFF

For R

= 12 kΩ

LIMIT

= 64%

For R

= 25 kΩ

LIMIT

= 34%

PI-2855-050602

Input

Voltage

CONTROL

47 kΩ

37.4 kΩ

QR can be an

optocoupler output or

can be replaced

by a manual switch.

ON/OFF

PI-2625-040501

Input

Voltage

ON/OFF

47 KΩ

can be an optocoupler

output or can be replaced by

a manual switch.

CONTROL

Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins (cont.)

DPA423-426

1/04

PI-2858-072602

Input

Voltage

CONTROL

47 kΩ

619 kΩ

ON/OFF For RLS = 619 kΩ

VUV = 33.3 V

VOV = 86.0 V

QR can be an optocoupler

output or can be replaced

by a MOSFET or manual

switch.

ON/OFF

47 kΩ

PI-2859-050602

Input

Voltage

CONTROL

RIL

RLS

619 kΩ

DCMAX@36 V = 75%

DCMAX@72 V = 42%

For RIL = 12 kΩ

ILIMIT = 64%

QR can be an optocoupler

output or can be replaced

by a manual switch.

Figure 21. Active-on Remote ON/OFF with LINE-SENSE and

EXTERNAL CURRENT LIMIT. Figure 22. Active-off Remote ON/OFF with LINE-SENSE.

Figure 23. Line-Sensing and Externally Set Current Limit.

PI-2640-050602

Input

Voltage

CONTROL

ON/OFF

47 kΩ

QR can be an optocoupler

output.

For timing requirements,

see Figure 6.

Figure 24. Synchronization.

PI-2837-011904

Input

Voltage

CONTROL

RIL

RLS

12 kΩ

619 KΩ

For RLS = 619 kΩ

DCMAX@36 V = 75%

DCMAX@72 V = 42%

For RIL = 12 kΩ

ILIMIT = 64%

See Figure 34 for other

resistor values (RIL)

to select different ILIMIT

values

VUV = 33.3 V

VOV = 86.0 V

Typical Uses of LINE-SENSE (L) and EXTERNAL CURRENT LIMIT (X) Pins (cont.)

DPA423-426

1/04

Application Examples

Figure 25. A High Efficiency 30 W, 5 V, Telecom Input DC-DC Converter.

High Efficiency 30 W Forward Converter

The circuit shown in Figure 25 is a typical implementation of a

single output DC-DC converter using DPA-Switch in a forward

configuration with synchronous rectification. This design

delivers 30 W at 5 V, from a 36 VDC to 75 VDC input with a

nominal efficiency at 48 VDC of 90% using the DPA425R.

By taking advantage of many of the built-in features of the

DPA-Switch, the design is greatly simplified compared to a

discrete implementation. Resistor R1 programs the input under-

voltage and overvoltage thresholds to typically 33 V and 86 V

respectively. This resistor also linearly reduces the maximum

duty from the internal maximum of 75% at 36 V to 42% at

72 V to prevent core saturation during load transients at high

input voltages. The DPA-Switch internal thresholds are

toleranced and characterized so the designer can guarantee the

converter will begin operation at 36 V, necessary to meet ETSI

standards, without the cost of an external reference IC.

The current limit is externally set by resistor R3 to just above the

drain current level needed for maximum load regulation to limit

the maximum overload power of the converter. The externally

programmable current limit feature also allows a larger

DPA-Switch family member to be selected. Using the X pin, the

current limit can be adjusted to the same level. A large device

reduces conduction losses and improves efficiency without

requiring any other circuit changes. This has been used here to

replace the DPA424R with a DPA425R.

The selectable 300/400 kHz switching frequency is set to 300 kHz

by connecting the FREQUENCY (F) pin to CONTROL (C).

DRAIN voltage clamping is provided by VR1, which keeps the

peak DRAIN voltage within acceptable limits. Transformer

core reset is provided by the gate capacitance of Q1 with R17

in series. Optional reset capacitance C9 with R5 can be added

if necessary to supplement the gate capacitance of Q1.

The output of the transformer is rectified using MOSFETs to

provide synchronous rectification. The UV/OV function,

together with the turns ratio of the transformer, defines the

maximum MOSFET gate voltage, allowing the very simple

gate drive arrangement, without the need for drive windings or

a drive IC. During primary on-time, capacitor C17 couples

charge through resistor R15 to drive the gate of the forward

MOSFET, Q2. Capacitor C17 provides a DC isolated drive for

Q2, preventing gate overstress on Q1 during power down. The

time constant formed by R16 and C17 is selected to be much

longer than one switching cycle. Diode D4 resets the voltage

on capacitor C17 before the next switching cycle. During the

primary off-time, the diode D2 provides a conduction path for

the energy in inductor L2 while Q1 is still off. The transformer

DPA425R

BAV

19WS

220 nF

VR1

SMBJ

150 C6

68 µF

10 V

1 nF

1.5 kV R14

10 Ω

18.2 kΩ

619 kΩ

1.0 Ω

C10

100 µF

10 V

C11

100 µF

10 V

C12

1 µF

10 V

36-75 VDC

1 µH

2.5 A L2

C1, C2 & C3

1 µF

100 V

SXF

CONTROL

PC357N1T

PI-3472-051303

DPA-Switch

5 V, 6 A

RTN

Si4888

C9* R5*

*Optional components

R15

10 ΩR16

10 kΩ

BAV19WS

R17

10 ΩQ1

Si4888

4.7 µF

20 V U2

BAV19WS

LM431AIM3

220 Ω

R11

10.0 kΩ

R10

10.0 kΩ

R12

5.1 Ω

10 kΩ

C14

1 µF

C13

10 µF

10 V

C16

100 nF

150 Ω

VIN

C17

3300 pF

DPA423-426

1/04

CONTROL

DPA-Switch

22 µF

10 V

0.1 µF

50 V C10

0.33 µF

C11

0.1 µF

1 µF

50 V

1 µF

10 V

330 µF

6 V

1 µH, 2A

330 µF

6 V

330 µF

6 V

1 µF

100 V

47 pF

200 V

VR1

SMAJ

150A

1 MΩ

8.66 kΩ

5.1 Ω

20 kΩ

34 kΩ

1 kΩ

100 Ω

51 Ω

619 kΩ

9, 101

6, 7

DPA423G U2

PC357

CAT431L,

SOT23

BAV19, SOD323

SL43

36 - 57 VDC

J1-1

3.3 V, 2 A

J2-1

-V

J1-2

RTN

J2-2

36 - 57

VDC

PI-3806-012304

Figure 26. A Cost Effective 6.6 W, 3.3 V Flyback DC-DC Converter.

reset voltage on the secondary winding directly drives a positive

voltage on the gate of catch MOSFET, Q1. MOSFET Q1

provides a low loss conduction path for a substantial portion of

the primary off-time. An isolated auxiliary winding on L2,

rectified and filtered by D1 and C4, provides the bias supply for

the optocoupler transistor.Output regulation is achieved by

using secondary side voltage reference, U3. The resistor divider

formed by R10 and R11, together with the reference voltage,

determines the output voltage. Diode D3 and C13 form a soft-

finish network that, together with the internal duty cycle and

current limit soft-start of the DPA-Switch, prevent output

overshoot at start-up. Resistor R7 ensures that the soft-finish

capacitor is discharged quickly when the output falls out of

regulation.Control loop response is shaped by R6, C16, R12,

C14, R9, R4 and C5, providing a wide bandwidth and good

phase margin at gain crossover. Since the PWM control in

DPA-Switch is voltage mode, no slope compensation is required

for duty cycles above 50%.

Cost Effective 6.6 W Flyback Conveter

The DPA-Switch flyback power supply provides a cost effective

solution for high density PoE and VoIP DC-DC applications.

Figure 26 shows a typical implementation of a single output

flyback converter using the DPA423G. For applications that

require input to output isolation, this simple, low component

count design delivers 6.6 W at 3.3 V from a 36 VDC to 57 VDC

input with a nominal efficiency at 48 VDC of 80%.

Resistor R2 programs the input under-voltage and overvoltage

thresholds to 33 V and 86 V respectively. Resistors R1 and R3

program the internal device current limit. The addition of line

sense resistor R1 reduces the current limit with increasing input

voltage, preventing excessive overload output current. In this

design the overload output current varies less than ±2.5% across

the entire input voltage range. Controlling the current limit also

reduces secondary component stress and leakage inductance

spikes, allowing the use of a lower VRRM (30 V rather than 40 V)

Schottky output diode, D2.

The primary side Zener clamp VR1 ensures the peak drain

voltage is kept below the 220 V BVDSS rating of U1 under input

surge and overvoltage events. During normal operation, VR1

does not conduct and C2 is sufficient to limit the peak drain

voltage.

The primary bias winding provides CONTROL pin current

after start-up. Diode D3 rectifies the bias winding, while

components R5 and C8 reduce high frequency switching noise

and prevent peak charging of the bias voltage. Capacitor C3

provides local decoupling of U1 and should be physically close

to the CONTROL and SOURCE pins. Energy storage for start-

up and auto-restart timing is provided by C4.

The secondary is rectified by D2 and the Low ESR tantalum

output capacitors, C5-C7, minimizing switching ripple and

maximizing efficiency. A small footprint secondary output

choke L1 and ceramic output capacitor C9 are adequate to

reduce high frequency noise and ripple to below 35 mV peak-

peak under full load conditions.

The output voltage is sensed by the voltage divider formed by

DPA423-426

1/04

Table 4. Output Power Table for 24 VDC Minimum Input Voltage

(See Table 3 for Notes).

PRODUCT3

OUTPUT POWER TABLE

5 W 7 W - - - 7.5 W

7 W 10 W 15 W - - 15.5 W

10 W 14 W 22 W 27 W 31 W

12 W16.5 W 25 W 31 W 37 W 43 W

DPA423

DPA424

DPA425

DPA426

16-32 VDC RANGE (FORWARD)2

Total Device

Dissipation 0.5 W 1 W 2.5 W 4 W 6 W Max

Power

Output1

PRODUCT3

OUTPUT POWER TABLE

8 W 11 W - - - 11.5 W

11 W 16 W 23.5 W - - 25 W

16 W 22 W 35 W 43 W 47 W

18 W 25 W 39 W 48 W 58 W 65 W

DPA423

DPA424

DPA425

DPA426

24-48 VDC RANGE (FORWARD)2

Total Device

Dissipation 0.5 W 1 W 2.5 W 4 W 6 W Max

Power

Output1

Table 3. Output Power Table for 16 VDC Minimum Input Voltage.

Notes: 1. Maximum output power is limited by device internal

current limit. 2. See text in this section for a complete description of

assumptions. 3. See Part Ordering Information.

resistors R8 and R9 and is fed to the low voltage 1.24 V

reference U3. Feedback compensation is provided by R6, R7

and C11 together with C4 and R4. Capacitor C10 provides a

soft-finish characteristic, preventing output overshoot during

start-up.

Key Application Considerations

DPA-Switch

Design Considerations

Power Table

This section provides a description of the assumptions used to

generate the power tables (Tables 1 and 3 through 6) and

explains how to use the information provided by them.

All Power tables: Tables 1 and 3 through 6

•Maximum output power is limited by the device internal

current limit. This is the peak output power which could

become the continuous output power, provided adequate

heat sinking is used.

•Data assumes adequate heat sinking to keep the junction

temperature at or below 100 °C and worst case RDS(ON) at

TJ = 100 °C.

•The use of P and G packages are recommended for device

dissipation equal to or less than 1.5 W only due to package

thermal limitation. For device dissipation above 1.5 W, use

R package.

Forward power tables: Tables 1 (upper half), 3 and 4

•Output power figures are based on forward topology using

Schottky diode rectification. Up to 5% higher output power

is possible using synchronous rectification.

•Dissipation data assumes a diode loss representing 6% of the

total output power and combined loss in magnetic components

representing 6% of the total output power. DPA-Switch

losses are based on a ratio between conduction and switching

losses of approximately 3:1. These assumptions are typical

for a single 5 V output forward converter design using

Schottky rectification and adequately designed magnetic

components.

Flyback power tables: Tables 1 (lower half), 5 and 6

•Output power and dissipation figures are based on a 5 V

output using Schottky diode rectification with an efficiency

of 85%. Values are generated by calculation based on

I2 • RDS(ON) losses and characterization of switching losses,

correlated to bench measurement of each DPA-Switch device.

•Device dissipations above 1.5 W are possible using the

R package. However the forward converter topology is

recommended for such higher power designs.

The power tables provide two types of information. The first is

the expected device dissipation for a given output power. The

second is the maximum power output. Each table specifies the

input voltage range and assumes a single 5 V output using

Schottky diode rectification.

Table 5. Flyback Output Power Table for 16 VDC Minimum Input

Voltage (See Table 3 for Notes).

PRODUCT3

OUTPUT POWER TABLE

5 W - - - 6 W

6.5 W 8.5 W 10 W - 11 W

7 W 10 W 12 W 15 W 22 W

DPA423

DPA424

DPA425

16-32 VDC RANGE (FLYBACK)2

Total Device

Dissipation 0.5 W 0.75 W 1 W 1.5 W Max

Power

Output1

For example, referring to Table 1, for 36-75 VDC input range,

DPA424 would typically dissipate 1 W in a 23 W forward

converter and has a maximum power capacity of 35 W. In the

same converter, DPA425 would dissipate 0.5 W. Selecting

DPA425 with associated reduced dissipation would increase

overall converter efficiency by approximately 2%.

Issues Affecting Dissipation:

1) Using synchronous rectification will tend to reduce device

dissipation.

DPA423-426

1/04

2) Designs with lower output voltages and higher currents will

tend to increase the device dissipation listed in the power table.

3) Reduced input voltage decreases the available output power

for the same device dissipation. Tables 3 to 6 are the power

tables for 16 VDC and 24 VDC input voltages. Input voltages

below 16 V are possible, but since the internal start-up current

source is not specified at voltages below 16 V, an external chip

supply current should be fed into the CONTROL pin

approximately equal to but less than ICD1.

DPA-Switch Selection

Use Tables 1 and 3 through 6 to select the DPA-Switch based on

device dissipation. Selecting the optimum DPA-Switch depends

upon required maximum output power, efficiency, heat sinking

constraints and cost goals. With the option to externally reduce

current limit, a larger DPA-Switch may be used for lower power

applications where higher efficiency is needed or minimal heat

sinking is available. Generally, selecting the next larger device,

than is required for power delivery will give the highest efficiency.

Selecting even larger devices may give little or no improvement

in efficiency due to the improvement in conduction losses being

negated by larger device switching losses. Figure 50 provides

information on switching losses. This together with conduction

loss calculations give an estimate of device dissipation.

Primary Clamp

A primary clamp network is recommended to keep the peak

DRAIN voltage due to primary leakage inductance to below the

BVDSS specification. A Zener diode combined with a small value

capacitor connected across the primary winding is a low cost and

low part count implementation.

Output Rectification

Rectification of the secondary is typically performed using Schottky

diodes or synchronous rectification. Schottky diodes are selected

for peak inverse voltage, output current, forward drop and thermal

conditions. Synchronous rectification requires the additional

complication of providing gate drive. The specified line under-

voltage and line overvoltage thresholds of DPA-Switch simplifies

deriving gate drive directly from the transformer secondary

winding for many applications. The turns ratio of the transformer

together with the under/over-voltage thresholds defines the

minimum and maximum gate voltages, removing the need for

Zeners to clamp the gate voltage.

Soft-Start

Generally a power supply experiences maximum stress at start-up

before the feedback loop achieves regulation. For a period of 5 ms

the on-chip soft-start linearly increases the duty cycle from zero to

the default DCMAX at turn-on. In addition, the primary current limit

increases from 85% to 100% over the same period. This causes

the output voltage to rise in an orderly manner allowing time for

the feedback loop to take control of the duty cycle. This integrated

soft-start reduces the stress on the DPA-Switch MOSFET, clamp

circuit and output diode(s), and helps prevent transformer saturation

during start-up. Also, soft-start limits the amount of output

voltage overshoot, and in many applications eliminates the need

for a soft-finish capacitor. If necessary, to remove output overshoot,

a soft-finish capacitor may be added to the secondary reference.

Switching Frequency

The FREQUENCY pin of DPA-Switch offers a switching

frequency option of 400 kHz or 300 kHz. Operating at 300 kHz

will increase the amount of magnetization energy stored in the

transformer. This is ideal for applications using synchronous

rectification driven directly from the transformer secondary where

this energy can be used to drive the catch MOSFET gate.

Transformer Design

It is recommended that the forward converter transformer be

designed for maximum operating flux swing of 1500 Gauss and

a peak flux density of 3500 Gauss. When operating at the

maximum current limit of the selected DPA-Switch (during

overload conditions), neither magnetic component (transformer

and output inductor) should be allowed to saturate. When a larger

device than necessary has been selected, reducing the internal

current limit close to the operating peak current limits overload

power and minimizes the size of the secondary components.

No-load and Standby Consumption

Cycle skipping operation at light or no load can significantly

reduce power loss. In addition this operating mode ensures that

the output maintains regulation even without an external minimum

load. However, if cycle skipping is undesirable in a particular

application, it can be avoided by adding sufficient pre-load.

DPA-Switch

Layout Considerations

The DPA-Switch can operate with large DRAIN current, the

following guidelines should be carefully followed.

Table 6. Flyback Output Power Table for 24 VDC Minimum Input

Voltage.

Notes: 1. Maximum output power is limited by device internal

current limit. 2. See text in this section for a complete description of

assumptions. 3. See Part Ordering Information. 4. Due to higher switching

losses, the DPA425 may not deliver additional power compared to a

smaller device.

PRODUCT3

OUTPUT POWER TABLE

7 W - - - 8.5 W

8.5 W 11.5 W 14 W - 17 W

-4-4-4-34 W

DPA423

DPA424

DPA425

24-48 VDC RANGE (FLYBACK)2

Total Device

Dissipation 0.5 W 0.75 W 1 W 1.5 W Max

Power

Output1

DPA423-426

1/04

Primary Side Connections

The tab of DPA-Switch R package is the intended return path for

the high switching currents. Therefore, the tab should be

connected by wide, low impedance traces back to the input

decoupling capacitor. The SOURCE pin should not be used to

return the power currents; incorrect operation of the device may

result. The SOURCE is only intended as a signal ground. The

device tab (SOURCE) is the correct connection for power

currents with the R package.

The CONTROL pin bypass capacitor should be located as

close as possible to the SOURCE and CONTROL pins and its

SOURCE connection trace should not be shared by the main

MOSFET switching currents. All SOURCE pin referenced

components connected to the LINE-SENSE or EXTERNAL

CURRENT LIMIT pins should also be located closely between

their respective pin and SOURCE. Once again, the SOURCE

connection trace of these components should not be shared by

the main MOSFET switching currents. It is critical that

the tab (SOURCE) power switching currents are returned to the

input capacitor through a separate trace that is not

shared by the components connected to CONTROL,

LINE-SENSE or EXTERNAL CURRENT LIMIT pins.

Any traces to the L or X pins should be kept as short as possible

and away from the DRAIN trace to prevent noise coupling.

LINE-SENSE resistor (R1 in Figure 25) should be located close

to the L pin to minimize the trace length on the L pin side.

In addition to the CONTROL pin capacitor (C6 in Figure 25),

a high frequency bypass capacitor in parallel is recommended

as close as possible between SOURCE and CONTROL pins for

better noise immunity. The feedback optocoupler output should

also be located close to the CONTROL and SOURCE pins of

DPA-Switch.

Heat Sinking

To maximize heat sinking of the DPA-Switch R or G package

and the other power components, special thermally conductive

PC board material (aluminum clad PC board) is recommended.

This has an aluminum sheet bonded to the PC board during the

manufacturing process to provide heat sinking directly and

allow the attachment of an external heat sink. If normal PC

board material is used (such as FR4), providing copper areas on

both sides of the board and using thicker copper will improve

heat sinking.

If an aluminum clad board is used then shielding of switching

nodes is recommended. This consists of an area of copper

placed directly underneath switching nodes such as the drain

node, and output diode to provide an electrostatic shield to

prevent coupling to the aluminum substrate. These areas are

connected to input negative in the case of the primary and output

return for secondary. This reduces the amount of capacitive

coupling into the insulated aluminum substrate that can then

appear on the output as ripple and high frequency noise.

Quick Design Checklist

As with any power supply design, all DPA-Switch designs

should be verified on the bench to make sure that component

specifications limits are not exceeded under worst case

conditions. The following minimum set of tests for DPA-Switch

forward converters is strongly recommended:

1. Maximum drain voltage – Verify that peak VDS does not

exceed minimum BVDSS at highest input voltage and

maximum overload output power. It is normal, however, to

have additional margin of approximately 25 V below BVDSS

to allow for other power supply component unit-to-unit

variations. Maximum overload output power occurs when

the output is loaded to a level just before the power supply

goes into auto-restart (loss of regulation).

2. Transformer reset margin – Drain voltage should also be

checked at highest input voltage with a severe load step (50-

100%) to verify adequate transformer reset margin. This test

shows the duty cycle at high input voltage, placing the most

demand on the transformer reset circuit.

3. Maximum drain current – At maximum ambient temperature,

maximum input voltage and maximum output load, verify

drain current waveforms at start-up for any signs of

transformer or output inductor saturation and excessive

leading edge current spikes. DPA-Switch has a leading edge

blanking time of 100 ns to prevent premature termination of

the on cycle. Verify that the leading edge current spike does

not extend beyond the blanking period.

4. Thermal check – At maximum output power, minimum

input voltage and maximum ambient temperature, verify

that temperature specifications are not exceeded for the

transformer, output diodes, output choke(s) and output

capacitors. The DPA-Switch is fully protected against over-

temperature conditions by its thermal shutdown feature. It is

recommended that sufficient heat sinking is provided to

keep the tab temperature at or below 115 °C (R package),

SOURCE pins at or below 100 °C (P/G packages) under

worst case continuous load conditions (at low input voltage,

maximum ambient and full load). This provides adequate

margin to minimum thermal shutdown temperature

(130 °C) to account for part-to-part RDS(ON) variation. When

monitoring device temperatures, note that the junction-to-

case thermal resistance should be accounted for when

estimating die temperature.

Design Tools

Up-to-date information on design tools is available at the Power

Integrations Web site: www.powerint.com.

DPA423-426

1/04

Figure 27. Layout Considerations for DPA-Switch Using R Package.

PI-2883-060602

Solder Side

Component Side

TOP VIEW

Transformer

Out

Maximize hatched copper area for optimum heat sinking

Via between board layers

Opto-

coupler

Inductor

(Coupled)

Output

Diode

DPA-Switch

Figure 28. Layout Considerations for DPA-Switch Using G Package.

PI-3805-012904

Opto-

coupler

Out

DPA-Switch Heatsink

Bottom Diode

Heatsink

V V

CL XF

SDS

DPA-Switch

Top Side PCB

Bottom Side PCB

(Two sided printed circuit board)

TOP VIEW

Maximize hatched copper area for optimum heat sinking

Via between board layers

DPA423-426

1/04

ABSOLUTE MAXIMUM RATINGS(1, 4)

DRAIN Voltage ............................................ -0.3 to 220 V

DRAIN Peak Current: DPA423 ...............................1.75 A

DPA424.................................3.5 A

DPA425....................................7 A

DPA426.................................9.6 A

CONTROL Voltage .......................................... -0.3 to 9 V

CONTROL Current ...............................................100 mA

LINE SENSE Pin Voltage ................................ -0.3 to 9 V

EXTERNAL CURRENT LIMIT Pin Voltage.. -0.3 to 9 V

FREQUENCY Pin Voltage............................... -0.3 to 9 V

TJ = 25 °C

fOSC

DCMIN

DCMAX

IC(skip)

CONTROL FUNCTIONS

Conditions

(Unless Otherwise Specified)

See Figure 32

SOURCE = 0 V; TJ = -40 to 125 °CMin Typ Max

Parameter Symbol Units

THERMAL IMPEDANCE

kHz

375 400 425

282 300 317

71 75 79

52 62 71

32 42 57

7.2 9.0

8.2 10.0

10.0 12.0

11.5 14.0

2 2.8 3.5

2.5 3.5 4.4

3.6 4.8 6.0

4.4 5.7 7.1

FREQUENCY Pin

Connected to SOURCE

FREQUENCY Pin

Connected to CONTROL

VL = 0 V

IL = 80 µA

IL = 115 µA

Storage Temperature ..................................... -65 to 150 °C

Operating Junction Temperature (2) ...............-40 to 150 °C

Lead Temperature (3) ............................................... 260 °C

Notes:

1. All voltages referenced to SOURCE, TA = 25 °C.

2. Normally limited by internal circuitry.

3. 1/16" from case for 5 seconds.

4. Maximum ratings specified may be applied, one at a time,

without causing permanent damage to the product.

Exposure to Absolute Maximum Rating conditions for

extended periods of time may affect product reliability.

DPA423

DPA424

DPA425

DPA426

DPA423

DPA424

DPA425

DPA426

TJ = 25 °C; fOSC = 400 kHz

Switching

Frequency

Duty Cycle (Prior

to Cycle Skipping)

Maximum Duty

Cycle

Control Current at

Start of Cycle

Skipping

External Bias

Current TJ = 25 °C; f OSC = 400 kHz

IC = I CD1

Notes:

1. Soldered to 0.36 sq. in. (232 mm2), 2 oz. (610 g/m2) copper clad.

2. Soldered to 1 sq. in (645 mm2), 2 oz. (610 g/m2) copper clad.

3. Measured on pin 7 (SOURCE) close to plastic interface.

4. Soldered to 1 sq. inch (645 mm2), 2 oz. (610 g/m2) copper clad.

5. Soldered to 3 sq. inch (1935 mm2), 2 oz. (610 g/m2) copper clad.

6. Measured at the back surface of tab.

Thermal Impedance: P or G Package:

(θJA) ......................70 °C/W(1); 60 °C/W(2)

(θJC)(3) ......................................... 11 °C/W

R Package:

(θJA) .........................................40 °C/W(4)

............................................................................ 30 °C/W(5)

(θJC)(6) ........................................... 2 °C/W

DPA423-426

1/04

CONTROL FUNCTIONS (cont.)

Conditions

(Unless Otherwise Specified)

See Figure 32

SOURCE = 0 V; TJ = -40 to 125 °CMin Typ Max

Parameter Symbol Units

During Startup and Auto-Restart:

VC=5.0 V; VD=16 V & 40 V; TJ=25 °C

DCreg

IC(CH)

%/mA/°C

Ω

%/°C

kHz

%/°C

SHUTDOWN/AUTO-RESTART

VC (AR)U

VC (AR)L

VC(AR)Hyst

DC(AR)

f(AR)

IUV

PWM Gain TJ = 25 °C; IC = (IC(skip) + IB)/2 -28 -22 -18 %/mA

-0.01

10 15 22

0.18

-5.2 -4 -3

-19

TJ = 25 °C; IC = (IC(skip) + IB)/2

PWM Gain

Temperature Drift

Dynamic

Impedance

Dynamic Impedance

Temperature Drift

CONTROL Pin

Internal Filter Pole

Average Current at the Beginning of

Softstart:

VC=5.0 V; VD=16 V & 40 V; TJ=25 °C

-0.6

5.8

4.5 4.8 5.1

0.8 1

3.8

48 50 52

44.5 47 49.5

CCONTROL = 22 µF; fOSC = 400 kHz;

VX = 0 V

CCONTROL = 22 µF; fOSC = 400 kHz;

VX = 0 V

Threshold from Off to On

Threshold from On to Off

Hysteresis

TJ = 25 °C

CONTROL Pin

Charging Current

Temperature Drift

Auto-restart Upper

Threshold Voltage

Auto-restart Lower

Threshold Voltage

Auto-restart

Hysteresis Voltage

Auto-restart Duty

Cycle

Auto-restart

Frequency

Line Under-

Voltage Threshold

Current and

Hysteresis (L pin)

LINE-SENSE (L) AND EXTERNAL CURRENT LIMIT (X) INPUTS

See Note A

µA

Softstart Time tSOFT TJ = 25 °C; DCMIN to DCMAX 57.2 ms

DPA423-426

1/04

Conditions

(Unless Otherwise Specified)

See Figure 32

SOURCE = 0 V; TJ = -40 to 125 °CMin Typ Max

Parameter Symbol Units

LINE-SENSE (L) AND EXTERNAL CURRENT LIMIT (X) INPUTS (cont)

Threshold from On to Off

Threshold from Off to On

Hysteresis

TJ = 25 °CµA

µA

µs

135 149

117 131

-27 -21.5 -16

-25.5

4.5

175 240 380

-230 -170

-270 -230 -185

-105 -85 -65

2.05 2.35 2.6

2.1 2.5 2.9

1.35

1.25

0.6 1.1

0.9 1.5

0.6 1 1.4

120 2250

120 3080

0.25 7.7

250

Line Overvoltage

or Remote ON/

OFF Threshold

Current and

Hysteresis (L pin)

Remote ON/OFF

Negative Thresh-

old Current and

Hysteresis (X pin)

L pin Short Circuit

Current

X pin Short Circuit

Current

L pin Voltage

(Positive Current)

X pin Voltage

(Negative Current)

Maximum Duty

Cycle Reduction

Onset Threshold

Current

Remote OFF

DRAIN Supply

Current

L pin Voltage

Turn-On Thresh-

old in Synchronous

Mode

On-Time

Pulse Width for

Synchronization

Off-Time

Pulse Width for

Synchronization

Synchronous Turn

On Delay

TJ = 25 °C

Threshold from On to Off

Threshold from Off to On

Hysteresis

IOV

IREM

IL(SC)

IX(SC)

IL(DC)

ID(RMT)

VL(TH)

ton(sync)

toff(sync)

tdelay(sync)

VL = VC

VL = 0 V

VX = 0 V Normal Mode

Remote OFF using L Pin

IL = IUV

IL = IOV

IX = -50 µA

IX = -150 µA

TJ = 25 °C

VL= Floating

VL=VC

VD = 40 V

VX = 0 V

From Synchronous On to Drain

Turn-On

fOSC = 400 kHz

fOSC = 300 kHz

DPA423-426

1/04

ON-State

Resistance

TJ = 25 °C

TJ = 100 °C

TJ = 25 °C

TJ = 100 °C

TJ = 25 °C

TJ = 100 °C

TJ = 25 °C

TJ = 100 °C

Ω

DPA423

ID = 300 mA

DPA424

ID = 600 mA

DPA425

ID = 1.25 A

DPA426

ID = 1.75 A

Conditions

(Unless Otherwise Specified)

See Figure 32

SOURCE = 0 V; TJ = -40 to 125 °CMin Typ Max

Parameter Symbol Units

FREQUENCY (F) INPUT

FREQUENCY Pin

Threshold Voltage

FREQUENCY Pin

Input Current

FREQUENCY Pin

Delay Time

VF = 0 V

Self Protection

Current Limit

(See Note B)

Initial Current Limit

Leading Edge

Blanking Time

Current Limit Delay

Thermal Shutdown

Temperature

Thermal Shutdown

Hysteresis

Power-up Reset

Threshold Voltage

1.1 4

-0.38

17 120

1.16 1.25 1.34

2.32 2.50 2.68

4.65 5.00 5.35

6.50 7.00 7.50

0.9 x

ILIMIT(min)

100

130 137 145

1.5 2.75 4

µA

µs

°C

IFVF = VC

tdelay(VF)

CIRCUIT PROTECTION

DPA423 di/dt = 300 mA/µs

DPA424 di/dt = 600 mA/µs

DPA425 di/dt = 1.25 A/µs

DPA426 di/dt = 1.75 A/µs

VD = 35 V

TJ = 25 °C

IC = (IC(skip) +IB)/2

IINIT

tLEB

tIL(D)

TJ(SD)

TJ(SD)hyst

VC(RESET)

ILIMIT TJ = 25 °C

OUTPUT

1.30 1.50

2.00 2.30

0.65 0.75

1.00 1.15

0.33 0.38

0.50 0.58

0.24 0.28

0.37 0.43

RDS(ON)

DPA423-426

1/04

5.6 5.85 6.0

±50

1.9 2.3 2.7

2.6 3.0 3.4

3.7 4.3 4.8

4.8 5.4 6

0.4 0.73 1.2

PPM/°C

VC(SHUNT)

lCD1

lCD2

See Note D

IC = (IC(skip) + IB)/2; TJ = 25 °C

IC = (IC(skip) + IB)/2

Output MOSFET Disabled

VL = 0 V; fOSC = 400 kHz

DRAIN Supply

Voltage

Shunt Regulator

Voltage

Shunt Regulator

Temperature Drift

CONTROL

Supply/Discharge

Current

Output

MOSFET Enabled

VL = 0 V;

fOSC = 400 kHz

Conditions

(Unless Otherwise Specified)

See Figure 32

SOURCE = 0 V; TJ = -40 to 125 °CMin Typ Max

Parameter Symbol Units

OUTPUT (cont)

IDSS

BVDSS

130

260

360

220

µA

VX, VL = Floating;

VD = 150 V;

TJ = 125 °C;

IC = (IC(skip) + IB)/2

DPA423

DPA424

DPA425

DPA426

VX, VL = Floating; TJ = 25 °C

IC = (IC(skip) + IB)/2; See Note C

OFF-State Drain

Leakage Current

Breakdown

Voltage

Rise Time

Fall Time

Measured in a Typical Application

SUPPLY VOLTAGE CHARACTERISTICS

DPA423

DPA424

DPA425

DPA426

NOTES:

A. For specifications with negative values, a negative temperature coefficient corresponds to an increase in

magnitude with increasing temperature, and a positive temperature coefficient corresponds to a decrease in

magnitude with increasing temperature.

B. For externally adjusted current limit values, please refer to Figure 34 (Current Limit vs. External Current Limit

Resistance) in the Typical Performance Characteristics section.

C.Breakdown voltage may be checked against minimum BVDSS specification by ramping the DRAIN pin voltage up to

but not exceeding minimum BVDSS.

D.It is possible to start up and operate

DPA-Switch

at DRAIN voltages well below 16 V. However, the CONTROL

pin charging current is reduced, which affects start-up time, auto-restart frequency, and auto-restart duty cycle.

Refer to Figure 44, the characteristic graph on CONTROL pin charge current (IC) vs. DRAIN voltage for low

voltage operation characteristics.

DPA423-426

1/04

120

100

00246810

CONTROL Pin Voltage (V)

CONTROL Pin Current (mA)

Slope

Dynamic

Impedance =

PI-2880-060302

Figure 30. CONTROL Pin I-V Characteristic.

Figure 29. Duty Cycle Measurement.

Figure 31. Typical Drain Operation Current Envelope.

Figure 32. DPA-Switch General Test Circuit.

PI-2860-050602

5-50 V

40 V

0-15 V 0.1 µF47 µF

470 Ω

5 W

470 Ω

0-200 kΩ

0-70 kΩ

NOTE: This test circuit is not applicable for current limit or output characteristic measurements.

SFX

CONTROL

DPA-Switch

PI-2039-033001

DRAIN

VOLTAGE

0 V

90%

10%

90%

D = t1

1.4

1.2

0.6

0.2

0.4

0.8

000.20.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Time (µs)

DRAIN Current (Normalized)

PI-2889-061302

tLEB (Blanking Time) +

tIL(D) (Current Limit Delay)

Temperature Range:

-40 °C to 125 °C

DPA423-426

1/04

The following precautions should be followed when testing

DPA-Switch by itself outside of a power supply. The schematic

shown in Figure 32 is suggested for laboratory testing of

DPA-Switch.

When the DRAIN pin supply is turned on, the part will be in the

auto-restart mode. The CONTROL pin voltage will be oscillating

at a low frequency between 4.8 and 5.8 V and the drain is turned

on every eighth cycle of the CONTROL pin oscillation. If the

CONTROL pin power supply is turned on while in this auto-

BENCH TEST PRECAUTIONS FOR EVALUATION OF ELECTRICAL CHARACTERISTICS

Typical Performance Characteristics

restart mode, there is only a 12.5% chance that the CONTROL

pin oscillation will be in the correct state (drain active state) so

that the continuous drain voltage waveform may be observed.

It is recommended that the VC power supply be turned on first

and the DRAIN pin power supply second if continuous drain

voltage waveforms are to be observed. The 12.5% chance of

being in the correct state is due to the divide-by-8 counter.

Temporarily shorting the CONTROL pin to the SOURCE pin

will reset DPA-Switch, which then will come up in the correct

state.

Figure 33. Current Limit vs. EXTERNAL CURRENT LIMIT Pin Current.

Figure 34. Current Limit vs. External Current Limit Resistance.

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.1

1.0

-230 -180 -130 -80 -30

IX (µA)

Current Limit

(Normalized to Internal Current Limit)

PI-2838-032202

0.3

0.2

0.1

0.5

0.4

0.6

0.7

0.8

0.9

1.0

1.1

051015 20 25 30 35

External Current Limit Resistor R

(kΩ)

Current Limit

(Normalized to Internal Current Limit)

PI-2839-032202

Minimum

Typical

Maximum

DPA423-426

1/04

Typical Performance Characteristics (cont.)

Figure 35. Frequency vs. Temperature. Figure 36. Internal Current Limit vs. Temperature.

Figure 37. External Current Limit vs. Temperature

with RIL =12 k

Ω

.Figure 38. Overvoltage Threshold vs. Temperature.

Figure 39. Under-Voltage Threshold vs. Temperature.

1.2

1.0

0.8

0.6

0.4

0.2

0-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

PI-2866-051702

Current Limit

(Normalized to 25 °C)

1.2

1.0

0.8

0.6

0.4

0.2

0-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

PI-2865-051702

Overvoltage Threshold

(Normalized to 25 °C)

Figure 40. LINE-SENSE Pin Voltage vs. Current.

1.2

1.0

0.8

0.6

0.4

0.2

0-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

PI-2867-051502

Under-Voltage Threshold

(Normalized to 25 °C)

7.0

4.0

6.0

5.0

0.0

-200 -100 -50-150 0 50 100 150 200 250

LINE-SENSE Pin Current (µA)

LINE-SENSE Pin Voltage (V)

PI-2871-051502

2.0

1.0

3.0

1.2

1.0

0.8

0.6

0.4

0.2

0-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

PI-2872-051602

Current Limit

(Normalized to 25 °C)

1.2

1.0

0.8

0.6

0.4

0.2

-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

PI-2868-051502

Output Frequency

(Normalized to 25 °C)

DPA423-426

1/04

1.1

1.0

0.9 -50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

Breakdown Voltage

(Normalized to 25 °C)

PI-176B-033001

Figure 46 Breakdown Voltage vs. Temperature.

Typical Performance Characteristics (cont.)

Figure 42. CONTROL Pin Current at Minimum Duty

Cycle vs. Temperature.

Figure 43. Max. Duty Cycle Reduction Onset Threshold

Current vs. Temperature.

Figure 41. EXTERNAL CURRENT LIMIT Pin Voltage

vs. Current.

1.6

1.0

1.4

1.2

0-225

-250 -150

-175

-200 -125 -50 -25

-100-75 0

EXTERNAL CURRENT LIMIT Pin Current (µA)

EXTERNAL CURRENT LIMIT

Pin Voltage (V)

PI-2869-051502

0.4

0.2

0.6

0.8

VX = 1.375 - IXx 843 kΩ

-200 µA

≤

-25 µA

Figure 44. IC vs. DRAIN Voltage.

1.2

0.8

1.0

-50 -20 0255075100 125 150

Junction Temperature (°C)

Remote OFF DRAIN Supply Current

(Normalized to 25 °C)

PI-2870-051502

0.2

0.4

0.6

Figure 45. Remote OFF DRAIN Supply Current

vs. Temperature.

1.2

1.0

0.8

0.6

0.4

0.2

0-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

PI-2864-051702

Onset Threshold Current

(Normalized to 25 °C)

5.0

3.5

3.0

4.0

4.5

0.00102030405060

DRAIN Voltage (V)

CONTROL Pin

Charging Current (mA)

PI-2841-051502

1.0

0.5

1.5

2.5

2.0

VC = 5 V

1.2

1.0

0.8

0.6

0.4

0.2

0-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

PI-2863-011904

CONTROL Pin Current

(Normalized to 25 °C)

DPA423-426

1/04

2.5

1.5

0.5

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

In-Circuit Peak Drain Current Normalized to

Nominal Device Internal Current Limit

PI-2877-052802

Switching Loss (Watts) at 400 kHz

Scaling Factors:

DPA423 = 0.08

DPA424 = 0.20

DPA425 = 0.55

DPA426 = 1.00

Data taken from a typical

forward converter design.

Typical Performance Characteristics (cont.)

Figure 49. COSS vs. DRAIN Voltage.

Figure 48. On-resistance vs. Temperature.

020406080100 120 140 160

100

1000

10000

PI-2851-011904

DRAIN Voltage (V)

Capacitance (pF)

Scaling Factors:

DPA423 = 0.18

DPA424 = 0.36

DPA425 = 0.72

DPA426 = 1.00

2.5

1.5

0.5

0-50 -25 0 25 7550 100 125 150

Temperature (°C)

PI-2850-011904

On-resistance

(Normalized to 25 °C)

Figure 50. Typical Switching Loss.

0012345

Drain Voltage (V)

PI-2849-050302

Drain Current (A)

Scaling Factors:

DPA423 = 0.18

DPA424 = 0.36

DPA425 = 0.72

DPA426 = 1.00

TCASE = 25 °C

TCASE = 100 °C

Figure 47 Output Characteristics.

DPA423-426

1/04

PART ORDERING INFORMATION

DPA-Switch

Product Family

Series Number

G Plastic Surface Mount DIP

P Plastic DIP

R Plastic TO-263-7C (available only with TL option)

Package/Lead Options

TL Tape & Reel, (G Package: 1000 min., R Package: 750 min.)

DPA 423 G - TL

(423, 424 & 425 only)

DPA423-426

1/04

PI-2076-101102

DIP-8

D S .004 (.10)

-E-

-D-

-F-

DIM

inches

0.367-0.387

0.240-0.260

0.125-0.145

0.015-0.040

0.120-0.140

0.057-0.068

0.014-0.022

0.008-0.015

0.100 BSC

0.030 (MIN)

0.300-0.320

0.300-0.390

0.300 BSC

9.32-9.83

6.10-6.60

3.18-3.68

0.38-1.02

3.05-3.56

1.45-1.73

0.36-0.56

0.20-0.38

2.54 BSC

0.76 (MIN)

7.62-8.13

7.62-9.91

7.62 BSC

Notes:

1. Package dimensions conform to JEDEC

specification MS-001-AB for standard dual in-line

(DIP) package .300 inch row spacing

(PLASTIC) 8 leads (issue B, 7/85).

2. Controlling dimensions are inches.

3. Dimensions shown do not include mold flash

or other protrusions. Mold flash or

protrusions shall not exceed .006 (.15) on any

side.

4. D, E and F are reference datums on the molded

body.

QP08A

PI-2077-041003

G08A

SMD-8

D S .004 (.10)

E S .010 (.25)

-E-

-D-

-F-

DIM

inches

0.367-0.387

0.240-0.260

0.125-0.145

0.004-0.012

0.036-0.044

0.057-0.068

0.048-0.053

0.032-0.037

0.007-0.011

0.010-0.012

0.100 BSC

0.030 (MIN)

0.372-0.388

0-8°

9.32-9.83

6.10-6.60

3.18-3.68

0.10-0.30

0.91-1.12

1.45-1.73

1.22-1.35

0.81-0.94

0.18-0.28

0.25-0.30

2.54 BSC

0.76 (MIN)

9.45-9.86

0-8°

Notes:

1. Package dimensions conform to JEDEC

specification MS-001-AB (issue B, 7/85)

except for lead shape and size.

2. Controlling dimensions are inches.

3. Dimensions shown do not include mold

flash or other protrusions. Mold flash or

protrusions shall not exceed .006 (.15) on

any side.

4. D, E and F are reference datums on the

molded body.

.004 (.10)

.010 (.25) M A S

.420

.046 .060 .060 .046

.080

Pin 1

.086

.186

.286

Solder Pad Dimensions

DPA423-426

1/04

.165 (4.19)

.185 (4.70)

R07C

TO-263-7C

PI-2664-112702

-A-

LD #1

.580 (14.73)

.620 (15.75)

.390 (9.91)

.420 (10.67)

.326 (8.28)

.336 (8.53)

.055 (1.40)

.066 (1.68)

.100 (2.54)

Ref.

.208 (5.28)

Ref.

.024 (0.61)

.034 (0.86)

.225 (5.72)

min.

.245 (6.22)

min.

.000 (0.00)

.010 (0.25)

.090 (2.29)

.110 (2.79)

.012 (0.30)

.024 (0.61)

°8 -°0

.045 (1.14)

.055 (1.40)

.050 (1.27)

Notes:

1. Package Outline Exclusive of Mold Flash & Metal Burr.

2. Package Outline Inclusive of Plating Thickness.

3. Foot Length Measured at Intercept Point Between

Datum A Lead Surface.

4. Controlling Dimensions are in Inches. Millimeter

Dimensions are shown in Parentheses.

.004 (0.10)

.315 (8.00)

.128 (3.25)

.038 (0.97)

.050 (1.27)

.380 (9.65)

.638 (16.21)

Solder Pad

Dimensions

DPA423-426

1/04

DPA423-426

1/04

Revision

Notes

1) Final release data sheet.

2) Updated Figure 25 and text description.

1) Corrected missing text on page 9 and corrected Table 4.

2) Updated R package description.

3) Revised thermal impedances (θJA), DCMIN, VF, IF, and BVDSS.

4) Updated Figure 25 and description in text.

1) Corrected text errors on pp. 1, 7 and 20.

1) Figure 25 and description in text updated.

1) Added P and G packages.

Date

6/02

9/02

4/03

5/03

1/04

DPA423-426

1/04

ITALY

Power Integrations S.r.l.

Via Vittorio Veneto 12,

Bresso

Milano, 20091, Italy

Phone: +39-028-928-6001

Fax: +39-028-928-6009

e-mail: eurosales@powerint.com

WORLD HEADQUARTERS

Power Integrations

5245 Hellyer Avenue

San Jose, CA 95138, USA.

Main: +1-408-414-9200

Customer Service:

Phone: +1-408-414-9665

Fax: +1-408-414-9765

e-mail: usasales@powerint.com

For the latest updates, visit our Web site: www.powerint.com

PATENT INFORMATION

Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power Integrations does not assume

any liability arising from the use of any device or circuit described herein, nor does it convey any license under its patent rights or the rights of others.

The products and applications illustrated herein (including circuits external to the products and transformer construction) may be covered by one or more U.S.

and foreign patents or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power Integrations’ patents

may be found at www.powerint.com.

LIFE SUPPORT POLICY

POWER INTEGRATIONS' PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS

WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF POWER INTEGRATIONS. As used herein:

1. Life support devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when

properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.

2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life

support device or system, or to affect its safety or effectiveness.

The PI logo,

TOPSwitch

TinySwitch

LinkSwitch

and

EcoSmart

are registered trademarks of Power Integrations.

PI Expert

and

DPA-Switch

SINGAPORE (ASIA PACIFIC

HEADQUARTERS)

Power Integrations, Singapore

51 Newton Road

#15-08/10 Goldhill Plaza

Singapore, 308900

Phone: +65-6358-2160

Fax: +65-6358-2015

e-mail: singaporesales@powerint.com

AMERICAS

Power Integrations

4335 South Lee Street, Suite G

Buford, GA 30518, USA

Phone: +1-678-714-6033

Fax: +1-678-714-6012

e-mail: usasales@powerint.com

CHINA (SHENZHEN)

Power Integrations

International Holdings, Inc.

Rm# 1705, Bao Hua Bldg.

1016 Hua Qiang Bei Lu

Shenzhen Guangdong,

518031, China

Phone: +86-755-8367-5143

Fax: +86-755-8377-9610

e-mail: chinasales@powerint.com

GERMANY

Power Integrations GmbH

Rueckertstrasse 3

D-80336, Muenchen, Germany

Phone: +49-89-5527-3910

Fax: +49-89-5527-3920

e-mail: eurosales@powerint.com

JAPAN

Power Integrations, K.K.

Keihin-Tatemono 1st Bldg.

12-20 Shin-Yokohama

2-Chome,

Kohoku-ku, Yokohama-shi,

Kanagawa 222-0033, Japan

Phone: +81-45-471-1021

Fax: +81-45-471-3717

e-mail: japansales@powerint.com

TAIWAN

Power Integrations

International Holdings, Inc.

5F-1, No. 316, Nei Hu Rd., Sec. 1

Nei Hu Dist.

Taipei, Taiwan 114, R.O.C.

Phone: +886-2-2659-4570

Fax: +886-2-2659-4550

e-mail: taiwansales@powerint.com

CHINA (SHANGHAI)

Power Integrations

International Holdings, Inc.

Rm 807, Pacheer

Commercial Centre

555 Nanjing West Road

Shanghai, 200041, China

Phone: +86-21-6215-5548

Fax: +86-21-6215-2468

e-mail: chinasales@powerint.com

INDIA (TECHNICAL SUPPORT)

Innovatech

261/A, Ground Floor

7th Main, 17th Cross,

Sadashivanagar

Bangalore 560080

Phone: +91-80-5113-8020

Fax: +91-80-5113-8023

e-mail: indiasales@powerint.com

KOREA

Power Integrations

International Holdings, Inc.

8th Floor, DongSung Bldg.

17-8 Yoido-dong,

Youngdeungpo-gu,

Seoul, 150-874, Korea

Phone: +82-2-782-2840

Fax: +82-2-782-4427

e-mail: koreasales@powerint.com

UK (EUROPE & AFRICA

HEADQUARTERS)

Power Integrations (Europe) Ltd.

1st Floor, St. James’s House

East Street

Farnham

Surrey

GU9 7TJ

United Kingdom

Phone: +44 (0) 1252-730-140

Fax: +44 (0) 1252-727-689

e-mail: eurosales@powerint.com

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World Wide +1-408-414-9660 World Wide +1-408-414-9760