®
TOP232-234
TOPSwitch-FX
Family
Design Flexible,
EcoSmart®
, Integrated
Off-line Switcher
Figure 1. Typical Flyback Application.
®
PART
ORDER
NUMBER3Adapter1Open
Frame2Open
Frame2
OUTPUT POWER TABLE
Table 1. Notes: 1. Typical continuous power in a non-ventilated
enclosed adapter measured at 50 ˚C ambient. 2. Maximum practical
continuous power in an open frame design with adequate heat sinking,
measured at 50 ˚C ambient. See key applications section for detailed
conditions. 3. Packages: P: DIP-8B, G: SMD-8B, Y: TO-220-7B.
PI-2503-073099
AC
IN DC
OUT
D
S
C
TOPSwitch-FX
CONTROL
M
+
-
F
July 2001
Product Highlights
Lower System Cost, High Design Flexibility
•Features eliminate or reduce cost of external components
•Fully integrated soft-start for minimum stress/overshoot
•Externally settable accurate current limit
•Wider duty cycle for more power, smaller input capacitor
•Line under-voltage (UV) detection: no turn off glitches
•Line overvoltage (OV) shutdown extends line surge limit
•Line feed forward with maximum duty cycle (DCMAX)
reduction rejects ripple and limits DCMAX at high line
•Single resistor sets OV/UV thresholds, DCMAX reduction
•Frequency jittering reduces EMI and EMI filtering costs
•Regulates to zero load without dummy loading
•132 kHz frequency reduces transformer/power supply size
•Half frequency option for video applications
•Hysteretic thermal shutdown for automatic recovery
•Large thermal hysteresis prevents PC board overheating
•Standard packages with omitted pins for large creepage
•Active-on and active-off remote ON/OFF capability
•Synchronizable to a lower frequency
EcoSmart
® - Energy Efficient
•Cycle skipping reduces no-load consumption
•Reduced consumption in remote off mode
•Half frequency option for high efficiency standby
•Allows shutdown/wake-up via LAN/input port
Description
TOPSwitch-FX uses the proven TOPSwitch topology and cost
effectively integrates many new functions that reduce system
cost and, at the same time, improve design flexibility,
performance and energy efficiency. Like TOPSwitch, the high
voltage power MOSFET, PWM control, fault protection and
other control circuitry are all integrated onto a single CMOS
chip, but with two added terminals. The first one is a MULTI-
FUNCTION (M) pin, which implements programmable line
OV/UV shutdown and line feed forward/DCMAX reduction with
line voltage. The same pin can be used instead to externally set
an accurate current limit. In either case, this pin can also be used
for remote ON/OFF or to synchronize the oscillator to an
external, lower frequency signal. The second added terminal is
the FREQUENCY (F) pin and is available only in the Y
package. This pin provides the half frequency option when
connected to CONTROL (C) instead of SOURCE (S). The
features on the new pins can be disabled by shorting them to the
SOURCE, which allows the device to operate in a three terminal
TOPSwitch mode, but with the following new transparent
features: soft-start, cycle skipping, 132 kHz switching frequency,
frequency jittering, wider DCMAX, hysteretic thermal shutdown
and larger creepage. In addition, all critical parameters such as
frequency, current limit, PWM gain, etc. have tighter temperature
and absolute tolerances compared to the TOPSwitch-II family.
Higher current limit accuracy and larger DCMAX, when combined
with other features allow for a 10% to 15% higher power
capability on the TOPSwitch-FX devices compared to equivalent
TOPSwitch-II devices for the same input/output conditions.
TOP232P
TOP232G
TOP232Y
TOP233P
TOP233G
TOP233Y
TOP234P
TOP234G
TOP234Y
230 VAC ±15%
Adapter1
85-265 VAC
9 W 15 W 6.5 W 10 W
10 W 25 W 7 W 15 W
13 W 25 W 9 W 15 W
20 W 50 W 15 W 30 W
16 W 30 W 11 W 20 W
30 W 75 W 20 W 45 W
TOP232-234
2B
7/01
Section List
Pin Functional Description.........................................................................................................................................3
TOPSwitch-FX Family Functional Description .........................................................................................................4
CONTROL (C) Pin Operation .................................................................................................................................4
Oscillator and Switching Frequency .......................................................................................................................5
Pulse Width Modulator and Maximum Duty Cycle .................................................................................................5
Minimum Duty Cycle and Cycle Skipping ...............................................................................................................6
Error Amplifier.........................................................................................................................................................6
On-chip Current Limit with External Programability................................................................................................6
Line Under-Voltage Detection (UV) ........................................................................................................................6
Line Overvoltage Shutdown (OV)...........................................................................................................................7
Line Feed Forward with DCMAX Reduction ..............................................................................................................7
Remote ON/OFF and Synchronization................................................................................................................... 7
Soft-Start ................................................................................................................................................................8
Shutdown/Auto-Restart ..........................................................................................................................................8
Hysteretic Over-Temperature Protection ................................................................................................................8
Bandgap Reference................................................................................................................................................8
High-Voltage Bias Current Source..........................................................................................................................8
Using FREQUENCY and MULTI-FUNCTION Pins .....................................................................................................9
FREQUENCY (F) Pin Operation.............................................................................................................................9
MULTI-FUNCTION (M) Pin Operation ....................................................................................................................9
Typical Uses of FREQUENCY (F) Pin ...................................................................................................................... 11
Typical Uses of MULTI-FUNCTION (M) Pin .............................................................................................................12
Application Examples...............................................................................................................................................14
A High Efficiency, 30 W, Universal Input Power Supply........................................................................................14
35 W Multiple Output Power Supply.....................................................................................................................15
17 W PC Standby Power Supply..........................................................................................................................16
Processor Controlled Supply Turn On/Off ............................................................................................................ 17
Key Application Considerations ..............................................................................................................................19
TOPSwitch-FX vs. TOPSwitch-ll...........................................................................................................................19
TOPSwitch-FX Design Considerations.................................................................................................................20
TOPSwitch-FX Selection................................................................................................................................20
Input Capacitor...............................................................................................................................................20
Primary Clamp and Output Reflected Voltage VOR .........................................................................................20
Output Diode ..................................................................................................................................................21
Soft-Start ........................................................................................................................................................21
EMI.................................................................................................................................................................21
Transformer Design........................................................................................................................................21
Standby Consumption....................................................................................................................................23
TOPSwitch-FX Layout Considerations .................................................................................................................23
Primary Side Connections..............................................................................................................................23
Y-Capacitor.....................................................................................................................................................23
Heat Sinking...................................................................................................................................................23
Quick Design Checklist.........................................................................................................................................23
Design Tools .........................................................................................................................................................23
Product Specifications and Test Conditions..........................................................................................................24
Typical Performance Characteristics ......................................................................................................................30
Package Outlines ......................................................................................................................................................34
TOP232-234
B
7/01 3
Figure 2. Functional Block Diagram.
Pin Functional Description
DRAIN (D) Pin:
High voltage power MOSFET drain output. The internal start-
up 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.
MULTI-FUNCTION (M) Pin:
Input pin for OV, UV, line feed forward with DCMAX reduction,
external set current limit, remote ON/OFF and synchronization.
A connection to SOURCE pin disables all functions on this pin
and makes TOPSwitch-FX operate in simple three terminal
mode (like TOPSwitch-II).
FREQUENCY (F) Pin: (Y package only)
Input pin for selecting switching frequency: 132 kHz if connected
to SOURCE pin and 66 kHz if connected to CONTROL pin.
Figure 3. Pin Configuration.
PI-2535-083099
The switching frequency is internally set for 132 kHz only
operation in P and G packages.
SOURCE (S) Pin:
Output MOSFET source connection for high voltage power
return. Primary side control circuit common and reference point.
SHUTDOWN/
AUTO-RESTART
PWM
COMPARATOR
CLOCK
SAW
HALF
FREQUENCY
OSCILLATOR WITH JITTER
CONTROLLED
TURN-ON
GATE DRIVER
CURRENT LIMIT
COMPARATOR
INTERNAL UV
COMPARATOR
INTERNAL
SUPPLY
5.8 V
4.8 V
SOURCE (S)
S
R
Q
Q
DMAX
STOP SOFT-
START
-
+
CONTROL (C)
MULTI-
FUNCTION (M)
FREQUENCY (F)
(Y Package Only)
-
+
5.8 V
IFB
RE
ZCVC
+
-
LEADING
EDGE
BLANKING
÷ 8
1
HYSTERETIC
THERMAL
SHUTDOWN
SHUNT REGULATOR/
ERROR AMPLIFIER
+
-
DRAIN (D)
ON/OFF
DCMAX
VBG
DCMAX
VBG + VT
0
OV/UV
VI (LIMIT)
CURRENT
LIMIT
ADJUST
LINE
SENSE
SOFT START
PI-2501-031901
Tab Internally
Connected to SOURCE Pin
Y Package (TO-220-7B)
P Package (DIP-8B)
G Package (SMD-8B)
CD
S
S
S
S
1 C
3 M
5 F
4 S
7 D
M8
5
7
1
4
2
3
TOP232-234
4B
7/01
TOPSwitch-FX
Family Functional Description
Figure 4. Relationship of Duty Cycle to CONTROL Pin Current.
PI-2504-072799
Duty Cycle (%)
I
C
(mA)
IM = 140 µA
IM = 190 µA
IM < IM(DC)
1.91.5 5.5 5.9
Slope = PWM Gain
I
CD1
I
B
Auto-restart
78
1.5
47
Like TOPSwitch, TOPSwitch-FX 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.
In addition to the three terminal TOPSwitch features, such as the
high voltage start-up, the cycle-by-cycle current limiting, loop
compensation circuitry, auto-restart, thermal shutdown, etc.,
the TOPSwitch-FX incorporates many additional functions that
reduce system cost, increase power supply performance and
design flexibility. 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.
Two terminals, FREQUENCY (available only in Y package)
and MULTI-FUNCTION, have been added to implement some
of the new functions. These terminals can be connected to the
SOURCE pin to operate the TOPSwitch-FX in a TOPSwitch-
like three terminal mode. However, even in this three terminal
mode, the TOPSwitch-FX offers many new transparent features
that do not require any external components:
1. A fully integrated 10 ms soft-start reduces peak currents and
voltages during start-up and practically eliminates output
overshoot in most applications.
2. DCMAX of 78% allows smaller input storage capacitor, lower
input voltage requirement and/or higher power capability.
3. Cycle skipping at minimum pulse width achieves regulation
and very low power consumption at no load.
4. Higher switching frequency of 132 kHz reduces the
transformer size with no noticeable impact on EMI or on
high line efficiency.
5. Frequency jittering reduces EMI.
6. Hysteretic over-temperature shutdown ensures automatic
recovery from thermal fault. Large hysteresis prevents circuit
board overheating.
7. Packages with omitted pins and lead forming provide large
DRAIN creepage distance.
8. Tighter absolute tolerances and smaller temperature vari-
ations on switching frequency, current limit and PWM gain.
The MULTI-FUNCTION pin is usually used for line sensing by
connecting a resistor from this pin to the rectified DC high
voltage bus to implement line over-voltage (OV)/under-voltage
(UV) and line feed forward with DCMAX reduction. In this
mode, the value of the resistor determines the OV/UV thresholds
and the DCMAX is reduced linearly starting from a line voltage
above the under-voltage threshold. In high efficiency
applications, this pin can be used in the external current limit
mode instead, to reduce the current limit externally (to a value
close to the operating peak current), by connecting the pin to
SOURCE through a resistor. The same pin can also be used as
a remote ON/OFF and a synchronization input in both modes.
The FREQUENCY pin in the TO-220 package sets the switching
frequency to the default value of 132 kHz when connected to
SOURCE pin. A half frequency option can be chosen by
connecting this pin to CONTROL pin instead. Leaving this pin
open is not recommended.
CONTROL (C) 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 rectified DC high voltage is applied to the DRAIN pin
during start-up, the MOSFET is initially off, and the CONTROL
pin capacitor is charged through a switched high voltage current
source connected internally between the DRAIN and CONTROL
pins. When the CONTROL pin voltage VC reaches
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 10 ms. If no external feedback/supply
current is fed into the CONTROL pin by the end of the soft-start,
the high voltage current source is turned off and the CONTROL
pin will start discharging in response to the supply current
drawn by the control circuitry. If the power supply is designed
properly, and no fault condition such as open loop or shorted
output exists, the feedback loop will close, providing external
TOP232-234
B
7/01 5
PI-2545-082299
S1 S2 S6 S7 S1 S2 S6 S7S0 S1 S7
S0 S0 5.8 V
4.8 V
S7
0 V
0 V
0 V
V
LINE
V
C
V
DRAIN
V
OUT
Note: S0 through S7 are the output states of the auto-restart counter
2
1234
0 V
~
~
~
~
~
~~
~~
~
S6 S7
~
~~
~
~
~
~
~
V
UV
~
~
~
~
~
~
~
~
~
~
S2
~
~
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 shorted 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 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 which 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 TOPSwitch-FX power dissipation 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 the
pulse width modulator/current limit latch at the beginning of
each cycle.
The nominal switching frequency of 132 kHz was chosen to
minimize transformer size while keeping the fundamental EMI
frequency below 150 kHz. The FREQUENCY pin (available
only in TO-220 package), when shorted to the CONTROL pin,
lowers the switching frequency to 66 kHz (half frequency)
which may be preferable in some cases such as noise sensitive
video applications or a high efficiency standby mode. Otherwise,
the FREQUENCY pin should be connected to the SOURCE pin
for the default 132 kHz. Trimming of the current reference
improves oscillator frequency accuracy.
To further reduce the EMI level, the switching frequency is
jittered (frequency modulated) by approximately ±4 kHz at
250 Hz (typical) rate as shown in Figure 6. Figure 28 shows the
typical improvement of EMI measurements with frequency
jitter.
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 7 kHz to reduce the
effect of switching noise in the chip supply current generated by
Figure 5. Typical Waveforms for (1) Power Up (2) Normal Operation (3) Auto-restart (4) Power Down .
TOP232-234
6B
7/01
Figure 6. Switching Frequency Jitter.
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
which 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 78% (typical). However, by connecting the MULTI-
FUNCTION pin to the rectified DC high voltage bus through a
resistor with appropriate value, the maximum duty cycle can be
made to decrease from 78% to 38% (typical) as shown in
Figure 8 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 0.4 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 at its
output consumes less power than the power that TOPSwitch-FX
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 operation 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 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. High drain
current causes VDS(ON) to exceed the threshold voltage and turns
the output MOSFET off until the start of the next clock cycle.
The default current limit of TOPSwitch-FX is preset internally.
However, with a resistor connected between MULTI-
FUNCTION pin and SOURCE pin, current limit can be
programmed externally to a lower level between 40% 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
TOPSwitch-FX that is bigger than necessary for the power
required can be used to take advantage of the lower RDS(ON) for
higher efficiency. With a second resistor connected between
the MULTI-FUNCTION pin and the rectified DC high voltage
bus providing a small amount of feed forward current, a true
power limiting operation against line variation can be
implemented. When using an RCD clamp, this feed forward
technique reduces maximum clamp voltage at high line allowing
for higher reflected voltage designs. 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 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 capacitances and secondary-side rectifier reverse
recovery time will not cause premature termination of the
switching pulse.
The current limit can be lower for a short period after the
leading edge blanking time as shown in Figure 33. This is due
to dynamic characteristics of the MOSFET. 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 TOPSwitch-FX off until the input line
PI-2550-092499
128 kHz
4 ms
Time
Switching
Frequency
V
DRAIN
136 kHz
TOP232-234
B
7/01 7
Figure 7. Synchronization Timing Diagram.
voltage reaches the under-voltage threshold. At power down,
UV prevents auto-restart attempts after the output goes out of
regulation. This eliminates power down glitches caused by the
slow discharge of input storage capacitor present in applications
such as standby supplies. A single resistor connected from the
MULTI-FUNCTION pin to the rectified DC high voltage bus
sets UV threshold during power up. Once the power supply is
successfully turned on, UV is disabled to allow extended input
voltage operating range. Input voltage is not checked again
until the power supply loses regulation and attempts another
turn-on. This is accomplished by enabling the UV comparator
only when the divide-by-8 counter used in auto-restart reaches
full count (S7) which is also the state that the counter is reset to
at power up (see Figure 5). The UV feature can be disabled
independent of OV feature as shown in Figure 16.
Line Overvoltage Shutdown (OV)
The same resistor used for UV also sets an overvoltage threshold
which, once exceeded, will force TOPSwitch-FX output into
off-state. The ratio of OV and UV thresholds is preset at 4.5
as can be seen in Figure 8. This feature turns off the
TOPSwitch-FX power MOSFET when the rectified DC high
voltage exceeds the OV threshold. When the MOSFET is off,
the rectified DC high voltage surge capability is increased to the
voltage rating of the MOSFET (700 V), due to the absence of
the reflected voltage and leakage spikes on the drain. Small
amount of hysteresis is provided on the OV threshold to prevent
noise triggering. The OV feature can be disabled independent
of UV feature as shown in Figure 15.
Line Feed Forward with DCMAX Reduction
The same resistor used for UV and OV also implements line
voltage feed forward which 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 IM. Note that for the same CONTROL pin current,
higher line voltage results in smaller operating duty cycle. As
an added safety measure, the maximum duty cycle DCMAX is
also reduced from 78% (typical) at a voltage slightly higher than
the UV threshold to 38% (typical) at the OV threshold (see
Figures 4, 8). DCMAX of 38% at the OV threshold was chosen
to ensure that the power capability of the TOPSwitch-FX is not
restricted by this feature under normal operation.
Remote ON/OFF and Synchronization
TOPSwitch-FX can be turned on or off by controlling the
current into or out from the MULTI-FUNCTION pin (see
Figure 8). This allows easy implementation of remote ON/OFF
control of TOPSwitch-FX in several different ways. A transistor
or an optocoupler output connected between the MULTI-
FUNCTION pin and the SOURCE pin implements this function
with “active-on” (Figure 19) while a transistor or an optocoupler
output connected between the MULTI-FUNCTION pin and the
CONTROL pin implements the function with “active-off”
(Figure 20).
When a signal is received at the MULTI-FUNCTION pin to
disable the output through any of the MULTI-FUNCTION pin
functions such as OV, UV and remote ON/OFF,
TOPSwitch-FX always completes its current switching cycle as
illustrated in Figure 7 before the output is forced off. The
internal oscillator is stopped slightly before the end of the
current cycle and stays there as long as the disable signal exists.
When the signal at the MULTI-FUNCTION pin changes state
from disable to enable, the internal oscillator starts the next
switching cycle. This approach allows the use of this pin to
synchronize TOPSwitch-FX to any external signal with a
frequency lower than its internal switching frequency.
PI-2558-092999
Oscillator
(SAW)
DMAX
Enable from
M Pin (STOP) Time
TOP232-234
8B
7/01
As seen above, the remote ON/OFF feature allows the
TOPSwitch-FX to be turned on and off instantly, on a cycle-by-
cycle basis, with very little delay. However, remote ON/OFF
can also be used as a standby or power switch to turn off the
TOPSwitch-FX and keep it in a very low power consumption
state for indefinitely long periods. If the TOPSwitch-FX is held
in remote off state for long enough time to allow the CONTROL
pin to dishcharge to the internal supply under-voltage threshold
of 4.8 V (approximately 32 ms for a 47 µF CONTROL pin
capacitance), the CONTROL pin goes into the hysteretic mode
of regulation. 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 runs entirely
off the high voltage DC input, but with very low power
consumption (160 mW typical at 230 VAC with M pin open).
When the TOPSwitch-FX 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 125 ms for a 47 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 such
as inkjet and laser printers. See Figure 27 under application
examples for more information.
Soft-Start
An on-chip soft-start function is activated at start-up with a
duration of 10 ms (typical). Maximum duty cycle starts from
zero and linearly increases to the default maximum of 78% at
the end of the 10 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 TOPSwitch-FX 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 described above. 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
Temperature protection is provided by a precision analog
circuit that turns the output MOSFET off when the junction
temperature exceeds the thermal shutdown temperature (135 ˚C
typical). When the junction temperature cools to below the
hysteretic temperature, normal operation resumes. A large
hysteresis of 70 ˚C (typical) is provided to prevent overheating
of the PC board due to a repeating fault condition. VC is
regulated in hysteretic mode and a 4.8 V to 5.8 V (typical)
sawtooth waveform is present on the CONTROL pin when the
power supply is turned off.
Bandgap Reference
All critical TOPSwitch-FX internal voltages are derived from a
temperature-compensated bandgap reference. This reference is
also used to generate a temperature-compensated current
reference which is trimmed to accurately set the switching
frequency, MOSFET gate drive current, current limit, and the
line OV/UV thresholds. TOPSwitch-FX 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 TOPSwitch-FX 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 35%. This
duty cycle is determined by the ratio of CONTROL pin charge
(IC) and discharge currents (ICD1 and ICD2). This current source
is turned off during normal operation when the output MOSFET
is switching.
TOP232-234
B
7/01 9
for line sensing by connecting a resistor from this pin to the
rectified DC high voltage bus to implement OV, UV and DCMAX
reduction with line voltage functions. In this mode, the value
of the resistor determines the line OV/UV thresholds, and the
DCMAX is reduced linearly with rectified DC high voltage
starting from just above the UV threshold. In high efficiency
applications this pin can be used in the external current limit
mode instead, 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 same pin can also be used
as a remote on/off and a synchronization input in both modes.
Please refer to Table 2 for possible combinations of the functions
with example circuits shown in Figure 13 through Figure 23. A
description of specific functions in terms of the MULTI-
FUNCTION pin I/V characteristic is shown in Figure 8. The
horizontal axis represents MULTI-FUNCTION 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)
and OV triggers at IOV (+225 µA typical). Between +50 µA and
+225 µA, the output is enabled. For external current limit and
line feed forward with DCMAX reduction, the vertical axis
represents the magnitude of the ILIMIT and DCMAX. Line feed
forward with DCMAX reduction lowers maximum duty cycle from
78% at IM(DC) (+90 µA typical) to 38% at IOV (+225 µA). External
current limit is available only with negative MULTI-FUNCTION
pin current. Please see graphs in the typical performance
characteristics section for the current limit programming range
and the selection of appropriate resistor value.
FREQUENCY (F) Pin Operation
The FREQUENCY pin is a digital input pin available in
TO-220 package only. Shorting the FREQUENCY pin to
SOURCE pin selects the nominal switching frequency of
132 kHz (Figure 10) which is suited for most applications. For
other cases that may benefit from lower switching frequency
such as noise sensitive video applications, a 66 kHz switching
frequency (half frequency) can be selected by shorting the
FREQUENCY pin to the CONTROL pin (Figure 11). In
addition, an example circuit shown in Figure 12 may be used to
lower the switching frequency from 132 kHz in normal operation
to 66 kHz in standby mode for very low standby power
consumption.
MULTI-FUNCTION (M) Pin Operation
When current is fed into the MULTI-FUNCTION pin, it works
as a voltage source of approximately 2.6 V up to a maximum
current of +400 µA (typical). At +400 µA, this pin turns into
a constant current sink. When current is drawn out of the
MULTI-FUNCTION pin, it works as a voltage source of
approximately 1.32 V up to a maximum current of –240 µA
(typical). At –240 µA, it turns into a constant current source.
Refer to Figure 9.
There are a total of five functions available through the use of
the MULTI-FUNCTION pin: OV, UV, line feed forward with
DCMAX reduction, external current limit and remote ON/OFF.
A short circuit between the MULTI-FUNCTION pin and
SOURCE pin disables all five functions and forces
TOPSwitch-FX to operate in a simple three terminal mode like
TOPSwitch-II. The MULTI-FUNCTION pin is typically used
✔
✔✔ ✔
✔✔ ✔
✔✔
✔
✔✔ ✔✔
✔✔✔✔✔
Table 2. Typical MULTI-FUNCTION Pin Configurations.
MULTI-FUNCTION PIN TABLE*
13 14 15 16 17 18 19 20 21 22 23
*This table is only a partial list of many MULTI-FUNCTION pin configurations that are possible.
Using FREQUENCY and MULTI-
FUNCTION Pins
▲
Figure Number
Three Terminal Operation
Under-Voltage
Overvoltage
Line Feed Forward (DCMAX)
Line Feed Forward (ILIMIT)
External Current Limit
Remote ON/OFF
TOP232-234
10 B
7/01
-250 -200 -150 -100 -50 0 50 100 150 200 250 300 350 400
PI-2524-081999
Output
MOSFET
Switching
(Enabled)
(Disabled)
ILIMIT (Default)
DCMAX (78.5%)
Current
Limit
Maximum
Duty Cycle
VBG
VBG + VTP
IM
IM
IM
IM
IUV
IREM(N) IOV
MULTI-
FUNCTION
Pin Voltage
Note: This figure provides idealized functional characteristics of the MULTI-FUNCTION pin with typical performance values.
Please refer to the parametric table and typical performance characteristics sections of the data sheet for measured data.
MULTI-FUNCTION Pin Current (µA)
Disabled when supply
output goes out of
regulation
Figure 8. MULTI-FUNCTION Pin Characteristics.
Figure 9. MULTI-FUNCTION Pin Input Simplified Schematic.
V
BG
+ V
T
V
BG
240 µA
400 µA
CONTROL Pin
MULTI-FUNCTION Pin
(Positive Current Sense - Under-Voltage,
Over-Voltage, Maximum Duty
Cycle Reduction)
(Negative Current Sense - ON/OFF,
Current Limit Adjustment)
PI-2548-092399
TOPSwitch-FX
TOP232-234
B
7/01 11
Figure 12. Half Frequency Standby Mode (For High Standby
Efficiency).
Figure 10. Full Frequency Operation (132 kHz). Figure 11. Half Frequency Operation (66 kHz).
Typical Uses of FREQUENCY (F) Pin
PI-2505-081199
DC
Input
Voltage
+
-
D
S
C
CONTROL
F
PI-2506-081199
DC
Input
Voltage
+
-
D
S
C
CONTROL
F
PI-2507-040401
DC
Input
Voltage
+
-
D
S
C
STANDBY
Q
S
can be an optocoupler output.
CONTROL
F
20 kΩ
R
HF
1 nF
Q
S
47 kΩ
TOP232-234
12 B
7/01
Figure 15. Line Sensing for Under-Voltage Only (Overvoltage
Disabled).
PI-2510-040401
DC
Input
Voltage
+
-
DM
S
C
V
UV
= R
LS
x I
UV
For Value Shown
V
UV
= 100 VDC
R
LS
6.2 V
2 MΩ
22 kΩ
CONTROL
Figure 16. Line Sensing for Overvoltage Only (Under-Voltage
Disabled).
Figure 17. Externally Set Current Limit.
PI-2517-040401
DC
Input
Voltage
+
-
DM
S
C
For R
IL
= 12 kΩ
I
LIMIT
= 67%
CONTROL
R
IL
See graph for other
resistor values (R
IL
)
For R
IL
= 25 kΩ
I
LIMIT
= 40%
PI-2516-040401
DC
Input
Voltage
+
-
DM
S
C
V
OV
= I
OV
x
R
LS
For Values Shown
V
OV
= 450 VDC
CONTROL
R
LS
IN4148
2 MΩ
30 kΩ
Figure 13. Three Terminal Operation (MULTI-FUNCTION
Features Disabled. FREQUENCY Pin Tied to SOURCE
or CONTROL Pin).
Figure 14. Line Sensing for Under-Voltage, Overvoltage and
Maximum Duty Cycle Reduction.
PI-2508-081199
DC
Input
Voltage
+
-
D
S
C
CONTROL
M
PI-2509-040401
DC
Input
Voltage
+
-
DM
S
C
V
UV
= I
UV
x R
LS
V
OV
=
I
OV
x
R
LS
For R
LS
= 2 MΩ
V
UV
= 100 VDC
V
OV
=
450 VDC
DC
MAX
@100 VDC = 78%
DC
MAX
@375 VDC = 47%
CONTROL
R
LS
2 MΩ
Typical Uses of MULTI-FUNCTION (M) Pin
Figure 18. Current Limit Reduction with Line Voltage.
PI-2518-040401
DC
Input
Voltage
+
-
DM
S
C
CONTROL
RIL
RLS 2.5 MΩ
6 kΩ
90% @ 100 VDC
55% @ 300 VDC
ILIMIT =
ILIMIT =
TOP232-234
B
7/01 13
PI-2522-040401
DC
Input
Voltage
+
-
D
S
C
R
MC
45 kΩ
M
CONTROL
Q
R
QR can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 kΩ
Figure 20. Active-off Remote ON/OFF.
Figure 19. Active-on (Fail Safe) Remote ON/OFF.
PI-2519-040401
DC
Input
Voltage
+
-
D
S
C
Q
R
ON/OFF
M
CONTROL
Q
R
can be an optocoupler
output or can be replaced by
a manual switch.
47 kΩ
PI-2523-040401
DC
Input
Voltage
+
-
D
S
C
RLS
M
For RLS = 2
MΩ
VUV = 100 VDC
VOV = 450 VDC
CONTROL
QR
2 MΩ
QR can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 kΩ
Figure 23. Active-off Remote ON/OFF with Line Sense.
Figure 22. Active-off Remote ON/OFF with Externally Set Current
Limit.
PI-2521-040401
DC
Input
Voltage
+
-
D
S
C
R
IL
R
MC
24 kΩ
12 kΩ
M
CONTROL
Q
R
2R
IL
R
MC
=
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 kΩ
Figure 21. Active-on Remote ON/OFF with Externally Set Current
Limit.
PI-2520-040401
DC
Input
Voltage
+
-
D
S
C
Q
R
R
IL
M
CONTROL
12 kΩ
For R
IL
=
I
LIMIT
= 67 %
Q
R
can be an optocoupler
output or can be replaced
by a manual switch.
ON/OFF 47 kΩ
25 kΩ
For R
IL
=
I
LIMIT
= 40 %
Typical Uses of MULTI-FUNCTION (M) Pin (cont.)
TOP232-234
14 B
7/01
Figure 24. 30 W Power Supply using External Current Limit.
Application Examples
A High Efficiency, 30 W, Universal Input Power Supply
The circuit shown in Figure 24 takes advantage of several of the
TOPSwitch-FX features to reduce system cost and power supply
size and to improve efficiency. This design delivers 30 W at
12 V, from an 85 to 265 VAC input, at an ambient of 50 ˚C, in
an open frame configuration. A nominal efficiency of 80% at
full load is achieved using TOP234.
The current limit is externally set by resistors R1 and R2 to a
value just above the low line operating peak current of
approximately 70% of the default current limit. This allows use
of a smaller transformer core size and/or higher transformer
primary inductance for a given output power, reducing
TOPSwitch-FX power dissipation, while at the same time
avoiding transformer core saturation during startup and output
transient conditions. The resistor R1 provides a feed forward
signal that reduces the current limit with increasing line voltage,
which, in turn, limits the maximum overload power at high
input line voltage. The feed forward function in combination
with the built-in soft-start feature of TOPSwitch-FX, allows the
use of a low cost RCD clamp (R3, C3 and D1) with a higher
reflected voltage, by safely limiting the TOPSwitch-FX drain
voltage, with adequate margin, under worst case conditions.
The extended maximum duty cycle feature of TOPSwitch-FX
(guaranteed minimum value of 75% vs. 64% for TOPSwitch-II)
allows the use of a smaller input capacitor (C1). The extended
maximum duty cycle and the higher reflected voltage possible
with the RCD clamp also permit the use of a higher primary to
secondary turns ratio for T1 which reduces the peak reverse
voltage experienced by the secondary rectifier D8. As a result,
a 60 V Schottky rectifier can be used for up to 15 V outputs,
which greatly improves power supply efficiency. The cycle
skipping feature of the TOPSwitch-FX eliminates the need for
any dummy loading for regulation at no load and reduces the no
load/standby consumption of the power supply. Frequency
jitter provides improved margin for conducted EMI meeting the
CISPR 22 (FCC B) specification.
A simple Zener sense circuit is used for low cost. The output
voltage is determined by the Zener diode (VR2) voltage and the
voltage drops across the optocoupler (U2) LED and resistor R6.
Resistor R8 provides bias current to Zener VR2 for typical
regulation of ±5% at the 12 V output level, over line and load
and component variations.
12 V
@ 2.5 A
D2
1N4148
T1
C5
47 µF
10 V
U2
LTV817A
VR2
1N5240C
10 V, 2%
R6
150 Ω
R15
150 Ω
C14
1 nF
D1
UF4005
R3
68 kΩ
2W
C3
4.7 nF
1KV
CY1
2.2 nF
U1
TOP234Y
DM
SF
C
TOPSwitch-FX
R8
150 Ω
C1
68 µF
400 V
C6
100 nF
D8
MBR1060 C10
560 µF
35 V
C12
220 µF
35 V
C11
560 µF
35 V
CONTROL
CONTROL
RTN
R5
6.8 Ω
R1
4.7 MΩ
1/2 W
R2
9.09 kΩ
PI-2525-040401
L3
3.3 µH
BR1
600 V
2A
F1
3.15 A
J1
L1
20 mH
L
N
CX1
100 nF
250 VAC
TOP232-234
B
7/01 15
Figure 25. 35 W Set-Top Box Power Supply.
35 W Multiple Output Power Supply
Figure 25 shows a five output, 35 W, secondary regulated
power supply utilizing a TOP233 for multiple output applications
such as set-top box, VCR, DVD, etc. The circuit shown is
designed for a 230 VAC input but can be used over the universal
range at a derated output power of 25 W. Alternatively, a
doubler input stage can be used at 100 or 115 VAC for the full
power rating of 35 W. TOPSwitch-FX provides several
advantages in the above mentioned applications.
A single line sense resistor R1 (2 MΩ) implements an under-
voltage detect (at 100 V), over-voltage shutdown (at 450 V) and
line feed forward with DCMAX reduction features. Under-
voltage detect ensures that the outputs are glitch free on power
down. The over-voltage shutdown turns off the TOPSwitch-FX
MOSFET above 450 V on the DC input rail, eliminating
reflected voltage and leakage inductance spikes, and hence,
extending the surge withstand to the 700 VDC rating of the
MOSFET. This feature prevents field failures in countries
where prolonged line voltage surges are common.
This design also takes advantage of soft-start and higher operating
frequency to reduce transformer size. A snubber circuit (R4,
C4) is used to slowdown dv/dt of the switching waveform
minimizing radiated video noise that could interfere with TV
reception. The half frequency option of the TOPSwitch-FX can
be used by connecting the FREQUENCY pin to the CONTROL
pin instead of the SOURCE pin in video noise sensitive
applications to allow for heavier snubbing without significant
impact on efficiency.
This design achieves ±5% load regulation on 3.3 V and 5 V
outputs using dual sensed optocoupler feedback through resistors
R9, R10 and R11. Other output voltages are set by the transformer
turns ratio. Output voltage on the low power -5 V output is shunt
regulated by resistor R12 and Zener diode VR2. Dummy load
resistor R13 is required to maintain regulation of the 30 V
output under light load conditions. Compensation of the TL431
(U3) is achieved with resistor R8 and capacitor C7. Primary
side compensation and auto-restart frequency are determined
by resistor R5 and capacitor C5. Second stage LC post-filtering
is used on the 3.3 V, 5 V and 18 V high power outputs (L2, L3,
L4 and C13, C15, C17) for low ripple. Full load operating
efficiency exceeds 75% across the AC input range. Primary
clamp components VR1 and D1 limit peak drain voltage to a
safe value.
The frequency jittering in TOPSwitch-FX helps reduce EMI,
maintaining emissions below CISPR 22 (FCC B) levels through
proper choice of Y1 capacitor (CY1) and input filtering elements
(CX1, L1). To minimize coupling of common mode transients
to the TOP233, Y1 capacitor is tied to the positive input DC rail.
Lightning strike immunity to 3 kV is attained with the addition
of a 275 V MOV (RV1).
5 V
@ 2.5 A
3.3 V
@ 3 A
RTN
D2
1N4148
T1 U2
LTV817
U3
TL431CLP
C8
22 µF
R6
51 Ω
R11
10.0 kΩ
C7
0.1 µF
R9
9.53 kΩ
R10
15.0 kΩ
R8
10 Ω
R7
510 Ω
D8
MUR120
D9
UF5402 C12
220 µF
25 V
CY1
2.2 nF
30 V
@ 100 mA
18 V
@ 550 mA
D1
UF4007
VR1
P6KE200
BR1
400 V
F1
3.15 A
RV1
275 V
J1
L1
20 mH
L
N
R5
6.8 Ω
C5
47 µF
C4
47 pF
TOP233Y
U1
DM
SF
C
TOPSwitch-FX
R1
2 MΩ
1/2 W
R13
24 kΩ
R4
2 kΩ
C1
33 µF
400 V
C6
100 nF
C10
100 µF
50 V
D10
MBR1045 C14
1000 µF
25 V
L3
3.3 µH
L4
3.3 µH
C15
100 µF
10 V
C13
100 µF
25 V
C11
1 µF
50 V
L2
3.3 µH
D11
BYW29-
100 C16
1000 µF
25 V
C18
330 µF
10 V R12
5 Ω
D12
1N5819 -5 V
@ 100 mA
CX1
0.1 µF
250 VAC
C17
100 µF
10 V
C19
100 µF
10 V
VR2
1N5231
PI-2536-040401
CONTROL
CONTROL
TOP232-234
16 B
7/01
17 W PC Standby Power Supply
Figure 26 shows a 17 W PC standby application with 3.3 V and
5 V secondary outputs and a 15 V primary output. The supply
uses the TOP232 operating from 230 VAC or 100/115 VAC
with doubler input. This design takes advantage of the soft-
start, line under-voltage detect, tighter current limit variation
and higher switching frequency features of TOPSwitch-FX. For
example, the higher switching frequency with tighter current
limit variation allows use of an EE19 transformer core.
Furthermore, the spacing between high voltage DRAIN pin and
low voltage pins of the TOPSwitch-FX packages provides large
creepage distance which is a significant advantage in high
pollution environments such as fan cooled PC power supplies.
Capacitor C1 provides high frequency decoupling of the high
voltage DC supply, and is necessary only if there is a long trace
length from the source of the DC supply to the inputs of this
standby circuit. The line sense resistor R1 senses the DC input
voltage for line under-voltage. When AC is turned off, the
under-voltage detect feature of the TOPSwitch-FX prevents
auto-restart glitches at the output caused by the slow discharge
of large storage capacitance in the main converter. This is
achieved by turning the power supply off when the input
voltage goes below a level needed to maintain output regulation
and keeping it off until the input voltage goes above the
under-voltage threshold (VUV), when the AC is turned on again.
The under voltage threshold is set at 200VDC, slightly below
the required lowest operating DC input voltage, for start-up at
170VAC. This feature saves several components needed to
implement the glitch free turn off with discrete or
TOPSwitch-II based designs.
The bias winding is rectified and filtered by D2 and C6 to create
a bias voltage for the TOP232 and to provide a 15V primary
bias output voltage for the main power supply primary control
circuitry. Both 3.3V and 5V output voltages are sensed by R9,
R10 and R11 using a TL431 (U3) circuit shown. Resistor R6
limits current through optocoupler U2 and sets overall AC
control loop gain. Resistor R7 assures that there is sufficient
bias current for the TL431 when the optocoupler is at a minimum
current. Capacitor C8 provides a soft-finish function to eliminate
turn-on overshoot. The no load regulation (cycle-skipping) of
TOPSwitch-FX permits the circuit to meet the low standby
power requirement of the Blue Angel specification for PCs.
Figure 26. 17 W PC Standby Supply.
3.3 V
@ 2 A
200-375
VDC
D2
BAV21
T1
C8
10 µF
35 V
C11
100 µF
10 V
C5
47 µF
U2
SFH615-2
U3
TL431CLP
C7
0.1 µF
R6
301 Ω
R9
16.2 kΩ
D1
UF4005
VR1
BZY97C-200
U1
TOP232Y
DM
SF
C
TOPSwitch-FX
R7
510 Ω
C1
0.01 µF
1 kV
(optional)
(Primary
Referenced)
C6
35 V
D4
SB540
D3
SB540
5 V
@ 2 A
C12
1000 µF
10 V
C10
1000 µF
10 V
CY1
1 nF
+
-
PI-2537-040401
RTN
15 V
@ 30 mA
R5
6.8 Ω
R1
3.9 MΩ
L2
3.3 µH
L1
3.3 µH
R10
12.1 kΩ
R11
10 kΩ
C13
100 µF
10 V
CONTROL
CONTROL
TOP232-234
B
7/01 17
Processor Controlled Supply Turn On/Off
A low cost momentary contact switch can be used to turn the
TOPSwitch-FX power on and off under microprocessor control
that may be required in some applications such as printers. The
low power remote off feature allows an elegant implementation
of this function with very few external components as shown in
Figure 27. Whenever the push button momentary contact switch
P1 is closed by the user, the optocoupler U3 is activated to
inform the microprocessor of this action. Initially, when the
power supply is off (M pin is floating), closing of P1 turns the
power supply on by shorting the M pin of the TOPSwitch-FX to
SOURCE through a diode (remote on). When the secondary
output voltage VCC is established, the microprocessor comes
alive and recognizes that the switch P1 is closed through the
switch status input that is driven by the optocoupler U3 output.
The microprocessor then sends a power supply control signal to
hold the power supply in the on-state through the optocoupler
U4. If the user presses the switch P1 again to command a turn
off, the microprocessor detects this through the optocoupler U3
and initiates a shutdown procedure that is product specific. For
example, in the case of the inkjet printer, the shutdown procedure
may include safely parking the print heads in the storage
position. In the case of products with a disk drive, the shutdown
procedure may include saving data or settings to the disk. After
the shutdown procedure is complete, when it is safe to turn off
the power supply, the microprocessor releases the M pin by
turning the optocoupler U4 off. If the manual switch and the
optocouplers U3 and U4 are not located close to the M pin, a
capacitor CM may be needed to prevent noise coupling to the pin
when it is open.
The power supply could also be turned on remotely through a
local area network or a parallel or serial port by driving the
optocoupler U4 input LED with a logic signal. Sometimes it is
easier to send a train of logic pulses through a cable (due to AC
coupling of cable, for example) instead of a DC logic level as
a wake-up signal. In this case, a simple RC filter can be used to
generate a DC level to drive U4 (not shown in Figure 27). This
remote on feature can be used to wake-up peripherals such as
printers, scanners, external modems, disk drives, etc., as needed
from a computer. Peripherals are usually designed to turn off
automatically if they are not being used for a period of time, to
save power.
Figure 27. Remote ON/OFF Using Microcontroller.
U1
U2
U4
U3
C
M
P1
PI-2561-040401
V
CC
(+5 V)
RETURN
CONTROL
High Voltage
DC Input
+
-
TOPSwitch-FX
DM
SF
C
1N4148
U4
LTV817A
6.8 kΩ
1 nF
100 kΩ
6.8 kΩ
U3
LTV817A
27 kΩ
1N4148
47 µFP1 Switch
Status
Power
Supply
ON/OFF
Control
External
Wake-up
Signal
LOGIC
INPUT LOGIC
OUTPUT
MICRO
PROCESSOR/
CONTROLLER
TOP232-234
18 B
7/01
In addition to using a minimum number of components,
TOPSwitch-FX provides many technical advantages in this
type of application:
1. Extremely low power consumption in the off mode: 80 mW
typical at 110 VAC and 160 mW typical at 230 VAC. This
is because in the remote/off mode the TOPSwitch-FX
consumes very little power, and the external circuitry does
not consume any current (M pin is open) from the high
voltage DC input.
2. A very low cost, low voltage/current, momentary contact
switch can be used.
3. No debouncing circuitry for the momentary switch is required.
During turn-on, the start-up time of the power supply
(typically 10 to 20 ms) plus the microprocessor initiation
time act as a debouncing filter, allowing a turn-on only if the
switch is depressed firmly for at least the above delay time.
During turn-off, the microprocessor initiates the shutdown
sequence when it detects the first closure of the switch, and
subsequent bouncing of the switch has no effect. If necessary,
the microprocessor could implement the switch debouncing
in software during turn-off, or a filter capacitor can be used
at the switch status input.
4. No external current limiting circuitry is needed for the
operation of the U4 optocoupler output due to internal
limiting of M pin current.
5. No high voltage resistors to the input DC voltage rail are
required to power the external circuitry in the primary. Even
the LED current for U3 can be derived from the CONTROL
pin. This not only saves components and simplifies layout,
but also eliminates the power loss associated with the high
voltage resistors in both on and off states.
6. Robust design: There is no on/off latch that can be accidentally
triggered by transients. Instead, the power supply is held in
the on-state through the secondary side microprocessor.
TOP232-234
B
7/01 19
Key Application Considerations
TOPSwitch-FX
vs.
TOPSwitch-ll
Table 3 compares the features and performance differences
between TOPSwitch-FX and TOPSwitch-II. Many of the new
features eliminate the need for costly discrete component.
Other features increase the robustness of design allowing cost
savings in the transformer and other power components.
*Not available
Table 3. Comparison Between TOPSwitch-II and TOPSwitch-FX. (continued on next page)
Function
TOPSwitch-II
TOPSwitch-FX
Figures Advantages
Soft-Start N/A* 10 ms •Limits peak current and voltage
component stresses during start-up
•Eliminates external components
used for soft-start in most
applications
•Minimizes output overshoot
External Current Limit N/A* Programmable 8, 17, •Smaller transformer
100% to 40% of 18, 21, •Higher efficiency
default current 22 •Allows tighter power limit
limit during output overload conditions
DCMAX 67% 78% 4 •Smaller input cap (wider dynamic
range)
•Higher power capability (when used
with RCD clamp for large VOR)
•Allows use of Schottky secondary
rectifier diode for up to 15 V output
for high efficiency
Line Feed Forward with N/A* 78% to 38% 4, 8, 14, •Rejects line ripple
DCMAX Reduction 23 •Increases transient and surge
voltage withstand capability
Line OV Shutdown N/A* Single resistor 8, 14, •Increases voltage withstand cap-
programmable 16, 23 ability against line surge
Line UV Detection N/A* Single resistor 5, 8, 14, •Prevents auto-restart glitches
programmable 15, 23 during power down
Switching Frequency 100 kHz ±10% 132 kHz ±7% 10 •Smaller transformer
•Fundamental below 150 kHz for
conducted EMI
Switching Frequency N/A* 66 kHz ±7% 11, 12 •Lower losses when using RC and
Option (TO-220 only) RCD snubber for noise reduction in
video applications
•Allows for higher efficiency in
standby mode
•Lower EMI (second harmonic below
150 kHz)
Frequency Jitter N/A* ±4 kHz@132 kHz 6, 28 •Reduces conducted EMI
±2 kHz@66 kHz
Cycle Skipping N/A* At DCMIN (1.5%) 4 •Zero load regulation without dummy
load
•Low power consumption at no load
TOP232-234
20 B
7/01
TOPSwitch-FX
Design Considerations
TOPSwitch-FX Selection
Selecting the optimum TOPSwitch-FX depends upon required
maximum output power, efficiency, heat sinking constraints
and cost goals. With the option to externally reduce current
limit, a larger TOPSwitch-FX may be used for lower power
applications where higher efficiency is needed or minimal heat
sinking is available.
Input Capacitor
The input capacitor must be chosen to provide the minimum
DC voltage required for the TOPSwitch-FX converter to maintain
regulation at the lowest specified input voltage and maximum
output power. Since TOPSwitch-FX has a higher DCMAX than
TOPSwitch-II, it is possible to use a smaller input capacitor. For
TOPSwitch-FX, a capacitance of 2 µF per watt is usually
sufficient for universal input with an appropriately designed
transformer.
Primary Clamp and Output Reflected Voltage VOR
A primary clamp is necessary to limit the peak TOPSwitch-FX
drain to source voltage. A Zener clamp (see Figure 26, VR1)
requires few parts and takes up little board space. For good
efficiency, the clamp Zener should be selected to be at least 1.5
times the output reflected voltage VOR as this keeps the leakage
spike conduction time short. When using a Zener clamp in a
universal input application, a VOR of less than 135 V is
recommended to allow for the absolute tolerances and
temperature variations of the Zener. This will ensure efficient
operation of the clamp circuit and will also keep the maximum
drain voltage below the rated breakdown voltage of the
TOPSwitch-FX MOSFET.
A high VOR is required to take full advantage of the wider DCMAX
of TOPSwitch-FX. An RCD clamp provides tighter clamp
voltage tolerance than a Zener clamp and allows a VOR as high
as 165 V. The VOR can be further increased in continuous mode
designs up to 185 V by reducing the external current limit as a
function of input line voltage (see Figure 18). The RCD clamp
*Not available
Table 3 (cont). Comparison Between TOPSwitch-II and TOPSwitch-FX.
Function
TOPSwitch-II TOPSwitch-FX
Figures Advantages
Remote ON/OFF N/A* Single transistor 8, 19, •Fast on/off (cycle by cycle)
or optocoupler 20, 21, •Active-on or active-off control
interface or manual 22, 23, •Low consumption in remote off state
switch 27 •Active-on control for fail-safe
•Eliminates expensive in-line on/off
switch
•Allows processor controlled turn on/
off
•Permits shutdown/wake-up of
peripherals via LAN or parallel port
Synchronization N/A* Single transistor •Synchronization to external lower
or optocoupler frequency signal
interface •Starts new switching cycle on
demand
Thermal Shutdown Latched Hysteretic (with •Automatic recovery from thermal
70 °C hysteresis) fault
•Large hysteresis prevents circuit
board overheating
Current Limit Tolerance ±10% (@25 °C) ±7% (@25 °C) •10% higher power capability due to
-8% (0 °C to100 °C) -4% (0 °C to 100 °C) tighter tolerance
DRAIN DIP 0.037" / 0.94 mm 0.137" / 3.48 mm •Greater immunity to arcing as a
Creepage at SMD 0.037" / 0.94 mm 0.137" / 3.48 mm result of build-up of dust, debris and
Package TO-220 0.046" / 1.17 mm 0.068" / 1.73 mm other contaminants
DRAIN Creepage at 0.045" / 1.14 mm 0.113" / 2.87 mm •Preformed leads accommodate
PCB for TO-220 (preformed leads) large creepage for PCB layout
•Easier to meet Safety (UL/VDE)
TOP232-234
B
7/01 21
is more cost effective than the Zener clamp but requires more
careful design (see quick design checklist).
Output Diode
The output diode is selected for peak inverse voltage, output
current, and thermal conditions in the application (including
heat sinking, air circulation, etc.). The higher DCMAX of
TOPSwitch-FX along with an appropriate transformer turns
ratio can allow the use of a 60 V Schoktty diode for higher
efficiency on output voltages as high as 15 V (See Figure 24. A
12 V, 30 W design using a 60 V Schottky for the output diode).
Soft-Start
Generally a power supply experiences maximum stress at start-
up before the feedback loop achieves regulation. For a period
of 10 ms the on-chip soft-start linearly increases the duty cycle
from zero to the default DCMAX at turn on, which causes the
primary current and output voltage to rise in an orderly manner
allowing time for the feedback loop to take control of the duty
cycle. This reduces the stress on the TOPSwitch-FX 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.
EMI
The frequency jitter feature modulates the switching frequency
over a narrow band as a means to reduce conducted EMI peaks
associated with the harmonics of the fundamental switching
frequency. This is particularly beneficial for average detection
mode. As can be seen in Figure 28, the benefits of jitter increase
with the order of the switching harmonic due to an increase in
frequency deviation.
The FREQUENCY pin of TOPSwitch-FX offers a switching
frequency option of 132 kHz or 66 kHz. In applications that
require heavy snubbers on the drain node for reducing high
frequency radiated noise (for example, video noise sensitive
applications such as VCR, DVD, monitor, TV, etc.), operating
at 66 kHz will reduce snubber loss resulting in better efficiency.
Also, in applications where transformer size is not a concern,
use of the 66 kHz option will provide lower EMI and higher
efficiency. Note that the second harmonic of 66 kHz is still
below 150 kHz, above which the conducted EMI specifications
get much tighter.
For 10 W or below, it is possible to use a simple inductor in place
of a more costly AC input common mode choke to meet
worldwide conducted EMI limits.
Transformer Design
It is recommended that the transformer be designed for maximum
operating flux density of 3000 gauss and a peak flux density of
4200 gauss at maximum current limit. The turns ratio should be
chosen for a reflected voltage (VOR) no greater than 135 V when
12
10
8
6
4
2
02nd 3rd 4th 5th
Switching Harmonic
PI-2559-093099
Noise Reduction (dB)
Quasi-Peak
Average
-20
-10
0
-10
20
30
40
50
60
70
80
0.15 1 10 30
Frequency (MHz)
Amplitude (dBµV)
PI-2576-010600
VFG243B (QP)
VF646B (AV)
TOPSwitch-II (no jitter)
VFG243B (QP)
VF646B (AV)
-20
-10
0
-10
20
30
40
50
60
70
80
0.15 1 10 30
Frequency (MHz)
Amplitude (dBµV)
PI-2577-010600
TOPSwitch-FX (with jitter)
(a)
(b)
(c)
Figure 28. (a) Conducted noise improvement for low frequency
harmonics due to jitter, (b) TOPSwitch-II full range EMI
scan (100kHz, no jitter), (c) TOPSwitch-FX full range
EMI scan (132 kHz, with jitter) with identical circuitry
and conditions.
TOP232-234
22 B
7/01
Figure 29. Layout Considerations for TOPSwitch-FX using DIP or SMD (Using Line Sensing for Under-Voltage and Overvoltage).
TOP VIEW
PI-2543-092199
Y1-
Capacitor
Opto-
coupler
D
+
-
HV J1
R1
+- DC
Out
Input Filter Capacitor
Output Filter Capacitor
Safety Spacing
T
r
a
n
s
f
o
r
m
e
r
Maximize hatched copper
areas ( ) for optimum
heat sinking
S
PRI SEC
S
S
SC
BIAS
M
TOPSwitch-FX
Figure 30. Layout Considerations for TOPSwitch-FX using TO-220 Package (Using Current Limit Reduction with Line Voltage).
TOP VIEW
PI-2544-092199
Y1-
Capacitor
Opto-
coupler
D
+
-
HV
+- DC
Out
Input Filter Capacitor
Heat Sink
Output Filter Capacitor
Safety Spacing
T
r
a
n
s
f
o
r
m
e
r
Maximize hatched copper
areas ( ) for optimum
heat sinking
PRI SEC
C
J1
R1
R2
TOPSwitch-FX
BIAS
T
r
a
n
s
f
o
r
m
e
r
M
S
F
TOP232-234
B
7/01 23
using a Zener clamp, 165 V when using an RCD clamp and
185 V when using RCD clamp with current limit feed forward.
For designs where operating current is significantly lower than
the default current limit, it is recommended to use an externally
set current limit close to the operating peak current to reduce
peak flux density and peak power (see Figure 17). In most
applications, the tighter current limit tolerance, higher switching
frequency and soft-start features of TOPSwitch-FX contribute
to a smaller transformer when compared to TOPSwitch-II.
Standby Consumption
Cycle skipping can significantly reduce power loss at zero load,
especially when a Zener clamp is used. For very low secondary
power consumption use a TL431 regulator for feedback control.
Alternately, switching losses can be significantly reduced by
switching from 132 kHz in normal operation to 66 kHz under
light load conditions.
TOPSwitch-FX
Layout Considerations
Primary Side Connections
Use a single point (Kelvin) connection at the negative terminal
of the input filter capacitor for TOPSwitch-FX SOURCE pin
and bias winding return. This improves surge capabilities by
returning surge currents from the bias winding directly to the
input filter capacitor.
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
MULTI-FUNCTION pin should also be located close to
SOURCE and MULTI-FUNCTION pins with dedicated SOURCE
pin connection. The MULTI-FUNCTION pin's trace should be
kept as short as possible and away from the DRAIN trace to
prevent noise coupling. Line sense resistor (R1 in Figures 29 and
30) should be located close to the MULTI-FUNCTION pin to
minimize the trace length on the MULTI-FUNCTION pin side.
In addition to the 47 µF CONTROL pin capacitor, a high frequency
bypass capacitor in parallel may be used for better noise immunity.
The feedback optocoupler output should also be located close to
the CONTROL and SOURCE pins of TOPSwitch-FX.
Y-Capacitor
The Y-capacitor should be connected close to the secondary
output return pin(s) and the primary DC input pin of the
transformer (see Figures 29 and 30).
Heat Sinking
The tab of the Y package (TO-220) is internally electrically
tied to the SOURCE pin. To avoid circulating currents, a heat
sink attached to the tab should not be electrically tied to any
nodes on the PC board.
When using P (DIP-8) or G (SMD-8) packages, a copper area
underneath the package connected to the SOURCE pins will act
as an effective heat sink.
In addition, sufficient copper area should be provided at the
anode and cathode leads of the output diode(s) for heat sinking.
Quick Design Checklist
As with any power supply design, all TOPSwitch-FX designs
should be verified on the bench to make sure that components
specifications are not exceeded under worst case conditions.
The following minimum set of tests is strongly recommended:
1. Maximum drain voltage – Verify that peak VDS does not
exceed 675 V at highest input voltage and maximum overload
output power. Maximum overload output power occurs
when the ouput is overloaded to a level just before the power
supply goes into auto-restart (loss of regulation).
2. 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 saturation and excessive leading edge current
spikes. TOPSwitch-FX has a leading edge blanking time of
200 ns to prevent premature termination of the on-cycle.
Verify that the leading edge current spike is below the
allowed current limit envelope (see Figure 33) for the drain
current waveform at the end of the 200 ns blanking period.
3. Thermal check – At maximum output power, minimum
input voltage and maximum ambient temperature, verify
that temperature specifications are not exceeded for
TOPSwitch-FX, transformer, output diodes and output
capacitors. Enough thermal margin should be allowed for
the part-to-part variation of the RDS(ON) of TOPSwitch-FX as
specified in the data sheet. The margin required can either
be calculated from the tolerances or it can be accounted for
by connecting an external resistance in series with the
DRAIN pin and attached to the same heatsink, having a
resistance value that is equal to the difference between the
measured RDS(ON) of the device under test and the worst case
maximum specification.
Design Tools
1. Technical literature: Data Sheet, Application Notes,
Design Ideas, etc.
2. Transformer design spreadsheet.
3. Engineering prototype boards.
Up to date information on design tools can be found at Power
Integrations Web site: www.powerint.com
TOP232-234
24 B
7/01
ABSOLUTE MAXIMUM RATINGS(1)
DRAIN Voltage ............................................ -0.3 to 700 V
DRAIN Peak Current: TOP232 .................................0.8 A
TOP233 .................................1.6 A
TOP234 .................................2.4 A
CONTROL Voltage .......................................... -0.3 to 9 V
CONTROL Current ...............................................100 mA
MULTI-FUNCTION Pin Voltage .................... -0.3 to 9 V
FREQUENCY Pin Voltage............................... -0.3 to 9 V
IC = 4 mA;
TJ = 25 °C
IC = ICD1
fOSC
∆f
fM
DCMAX
DCMIN
tSOFT
CONTROL FUNCTIONS
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
THERMAL IMPEDANCE
kHz
kHz
Hz
%
%
ms
%/mA
Thermal Impedance: Y Package (θJA)(1) ............... 70 °C/W
(θJC)(2) ................. 2 °C/W
P/G Package:
(θJA) ........45 °C/W(3); 35 °C/W(4)
(θJC)(5) .......................... 11 °C/W
Notes:
1. Free standing with no heatsink.
2. Measured at the back surface of tab.
3. Soldered to 0.36 sq. inch (232 mm2), 2oz. (610 gm/m 2) copper clad.
4. Soldered to 1 sq. inch (645 mm2), 2oz. (610 gm/m2) copper clad.
5. Measured on the SOURCE pin close to plastic interface.
124 132 140
61.5 66 70.5
± 4
± 2
250
75.0 78.0 82.0
35.0 47.0 57.0
0.8 1.5 2.7
10 14
-27 -22 -17
IC = 4 mA; TJ = 25 °C
Switching
Frequency
(average)
Frequency Jitter
Deviation
Frequency Jitter
Modulation Rate
Maximum Duty
Cycle
Minimum Duty
Cycle (Prior to
Cycle Skipping)
Soft Start Time
PWM
Gain
FREQUENCY Pin
Connected to SOURCE
FREQUENCY Pin
Connected to CONTROL
132 kHz Operation
66 kHz Operation
IM ≤ IM(DC)
IM = 190 µA
TJ = 25 °C; DCMIN to DCMAX
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.
TOP232-234
B
7/01 25
CONTROL FUNCTIONS (cont.)
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
See Note A
See Figure 4
TJ = 25 °C
IC = 4 mA; TJ = 25 °C
See Figure 32
lB
ZC
PWM Gain
Temperature Drift
External Bias
Current
CONTROL
Current at Start of
Cycle Skipping
Dynamic
Impedance
Dynamic
Impedance
Temperature Drift
Control Pin
Internal Filter Pole
%/mA/°C
mA
mA
Ω
%/°C
kHz
SHUTDOWN/AUTO-RESTART
VC = 0 V
VC = 5 V
lC (CH)
vC(AR)
Control Pin
Charging Current
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
mA
%/°C
V
V
V
%
Hz
-5.0 -3.8 -2.6
-3.0 -1.9 -0.8
0.5
5.8
4.5 4.8 5.1
0.8 1.0
248
1.0
TJ = 25 °C
See Note A
- 0.01
1.2 1.9 2.8
5.9 7.5
10 15 22
0.18
7
TOP232-234
26 B
7/01
MULTI-FUNCTION INPUT
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
lUV
IOV
IREM (N)
IM (SC)
VM
IM (DC)
TRON
TROFF
µA
µA
µA
µA
µA
µA
V
µA
%/µA
mA
µs
µs
44 50 54
210 225 240
10
-43 -35 -27
-7
300 400 520
-300 -240 -180
-110 -90 -70
2.00 2.60 3.00
2.50 2.90 3.30
1.25 1.32 1.39
1.18 1.24 1.30
75 90 110
0.30
0.6 1.1
1.0 1.8
1.5 2.5 4.0
1.5 2.5 4.0
TJ = 25 °C
MULTI-FUNCTION
Pin Floating
MULTI-FUNCTION
Pin Shorted to
CONTROL
TJ = 25 °C
Threshold
Hysteresis
TJ = 25 °C
VM = VC
Normal Mode
Auto-restart Mode
lM = 50 µA
lM = 225 µA
lM = -50 µA
lM = -150 µA
TJ = 25 °C
IM > IM (DC)
VDRAIN = 150 V
From Remote On to Drain Turn-On
See Note B
Minimum Time Before Drain
Turn-On to Disable Cycle
See Note B
VM = 0 V
Threshold
Hysteresis
Line Under-Voltage
Threshold Current
Line Over-Voltage
or Remote ON/
OFF Threshold
Current and
Hysteresis
Remote ON/OFF
Negative Threshold
Current and
Hysteresis
MULTI-FUNCTION
Pin Short Circuit
Current
MULTI-FUNCTION
Pin Voltage
Maximum Duty
Cycle Reduction
Onset Threshold
Current
Maximum Duty
Cycle Reduction
Slope
Remote OFF
DRAIN Supply
Current
Remote ON Delay
Remote OFF
Setup Time
TOP232-234
B
7/01 27
ILIMIT
IINIT
tLEB
tILD
VC(RESET)
RDS(ON)
A
A
ns
ns
°C
°C
V
Ω
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
CIRCUIT PROTECTION
See Figure 33
TJ = 25 °C
TJ = 25 °C
TJ = 100 °C
TJ = 25 °C
TJ = 100 °C
TJ = 25 °C
TJ = 100 °C
TOP232
ID = 50 mA
TOP233
ID = 100 mA
TOP234
ID = 150 mA
OUTPUT
FREQUENCY INPUT
FREQUENCY Pin
Threshold Voltage
FREQUENCY Pin
Input Current VF = VC
VF
IF
0.465 0.500 0.535
0.930 1.000 1.070
1.395 1.500 1.605
0.75 x
ILIMIT(MIN)
0.6 x
ILIMIT(MIN)
200
100
125 135 150
70
2.0 3.3 4.3
15.6 18.0
25.7 30.0
7.8 9.0
12.9 15.0
5.2 6.0
8.6 10.0
Self Protection
Current Limit
Initial Current Limit
Leading Edge
Blanking Time
Current Limit Delay
Thermal Shutdown
Temperature
Thermal Shutdown
Hysteresis
Power-up Reset
Threshold Voltage
ON-State
Resistance
TOP232
TJ= 25 °C
TOP233
TJ= 25 °C
TOP234
TJ= 25 °C
≤ 85 VAC
(Rectified Line Input)
265 VAC
(Rectified Line Input)
IC = 4 mA
IC = 4 mA
Figure 34, S1 open
Internal; di/dt = 100mA/µs
Internal; di/dt = 200mA/µs
Internal; di/dt = 300mA/µs
See Note B 1.0 2.9 VC -1.0 V
10 22 40 µA
See Note C
See Note C
See Note C
TOP232-234
28 B
7/01
100
50
36
5.60 5.85 6.10
±50
1.0 1.5 2.0
0.3 0.6 1.0
ns
ns
V
V
ppm/°C
mA
Conditions
(Unless Otherwise Specified)
See Figure 34
SOURCE = 0 V; TJ = -40 to 125 °C
Min Typ Max
Parameter Symbol Units
tR
tF
VC(SHUNT)
lCD1
lCD2
Measured in a Typical
Flyback Converter Application
See Note D
IC = 4 mA
Output
MOSFET Enabled
VM = 0 V
Output
MOSFET Disabled
VM = 0 V
SUPPLY VOLTAGE CHARACTERISTICS
OUTPUT (cont.)
Off-State
Current
Breakdown
Voltage
IDSS
BVDSS
150 µA
700 V
Rise
Time
Fall
Time
DRAIN Supply
Voltage
Shunt Regulator
Voltage
Shunt Regulator
Temperature Drift
Control Supply/
Discharge Current
VM = Floating; IC = 4mA
VDS = 560 V; TJ = 125 °C
VM = Floating; IC = 4mA
ID = 100 µA; TJ = 25 °C
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. Guaranteed by characterization. Not tested in production.
C.For externally adjusted current limit values, please refer to the graph (Current Limit vs. External Current Limit
Resistance) in the Typical Performance Characteristics section.
D.It is possible to start up and operate TOPSwitch-FX at DRAIN voltages well below 36 V. However, the CONTROL
pin charging current is reduced, which affects start-up time, auto-restart frequency, and auto-restart duty cycle.
Refer to the characteristic graph on CONTROL pin charge current (IC) vs. DRAIN voltage for low voltage operation
characteristics.
TOP232-234
B
7/01 29
Figure 32. CONTROL Pin I-V Characteristic.
Figure 31. Duty Cycle Measurement.
Figure 33. Drain Current Operating Envelope.
Figure 34. TOPSwitch-FX General Test Circuit.
PI-2538-040401
5-50 V
S4
0-60 kΩ
40 V
0-15 V 0.1 µF47 µF
470 Ω
5 W
470 Ω
100 kΩ
NOTES: 1. This test circuit is not applicable for current limit or output characteristic measurements.
2. For P and G packages, short all SOURCE pins together.
D
SF
C
M
CCONTROL
TOPSwitch-FX
S2
S3
S1
0.8
1.3
1.2
1.1
0.9
0.8
1.0
0012 6 83
Time (us)
DRAIN Current (normalized)
PI-2022-033001
45 7
0.7
0.6
0.5
0.4
0.3
0.2
0.1
ILIMIT(MAX) @ 25 °C
ILIMIT(MIN) @ 25 °C
IINIT(MIN) @ 85 VAC
IINIT(MIN) @ 265 VAC
tLEB (Blanking Time)
PI-2039-033001
DRAIN
VOLTAGE
HV
0 V
90%
10%
90%
t2
t1
D = t1
t2
120
100
80
40
20
60
00246810
CONTROL Pin Voltage (V)
CONTROL Pin Current (mA)
1
Slope
Dynamic
Impedance =
PI-1939-091996
TOP232-234
30 B
7/01
The following precautions should be followed when testing
TOPSwitch-FX by itself outside of a power supply. The schematic
shown in Figure 34 is suggested for laboratory testing of
TOPSwitch-FX.
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 TOPSwitch-FX, which then will come up in the
correct state.
.3
.4
.5
.6
.7
.8
.9
1.0
-250 -200 -150 -100 -50 0
I
M
(µA)
Current Limit (A)
CURRENT LIMIT vs. MULTI-FUNCTION
PIN CURRENT PI-2540-033001
60
80
100
120
140
160
180
200
di/dt (mA/µs)
TOP234 1.50
TOP233 1.00
TOP232 0.50
Scaling Factors:
.3
.4
.5
.6
.7
.8
.9
1.0
1.1
60
80
100
120
140
160
180
200
0 5K 10K 15K 20K 25K
External Current Limit Resistor R
IL
(Ω)
Current Limit (A)
di/dt (mA/µs)
CURRENT LIMIT vs. EXTERNAL
CURRENT LIMIT RESISTANCE
PI-2539-033001
30K
Maximum and minimum levels
are based on characterization.
Maximum
Minimum
Typical
TOP234 1.50
TOP233 1.00
TOP232 0.50
Scaling Factors:
TOP232-234
B
7/01 31
Typical Performance Characteristics (cont.)
1.1
1.0
0.9 -50 -25 0 25 50 75 100 125 150
Junction Temperature (°C)
Breakdown Voltage
(Normalized to 25 °C)
BREAKDOWN vs. TEMPERATURE
PI-176B-033001
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)
FREQUENCY vs. TEMPERATURE
PI-1123A-033001
Output Frequency
(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)
INTERNAL CURRENT LIMIT
vs. TEMPERATURE
PI-2555-033001
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)
EXTERNAL CURRENT LIMIT vs.
TEMPERATURE with R
IL = 12 kΩ
PI-2554-033001
Current Limit (A)
TOP234 1.50
TOP233 1.00
TOP232 0.50
Scaling Factors:
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)
OVER-VOLTAGE THRESHOLD
vs. TEMPERATURE
PI-2553-033001
Over-Voltage Threshold
(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)
UNDER-VOLTAGE THRESHOLD
vs. TEMPERATURE
PI-2552-033001
Under-Voltage Threshold
(Normalized to 25 °C)
TOP232-234
32 B
7/01
Typical Performance Characteristics (cont.)
1.2
1.4
1.6
0.4
0.6
0.2
0.8
1.0
0-300 -200 -150 -50-250 -100 0
MULTI-FUNCTION Pin Voltage (V)
MULTI-FUNCTION PIN VOLTAGE
vs. CURRENT (EXPANDED)
PI-2541-091699
MULTI-FUNCTION Pin Current (µA)
6
5
4
3
2
1
0-300 -200 -100 0 100 200 300 400 500
MULTI-FUNCTION PIN VOLTAGE
vs. CURRENT
PI-2542-091699
MULTI-FUNCTION Pin (V)
MULTI-FUNCTION Pin Current (µA)
See
Expanded
Version
2
1.2
1.6
0020 40 60 80 100
DRAIN Voltage (V)
CONTROL Pin
Charging Current (mA)
IC vs. DRAIN VOLTAGE
PI-2564-101499
0.4
0.8
V
C
= 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)
CONTROL CURRENT at START of
CYCLE SKIPPING vs. TEMPERATURE
PI-2562-033001
CONTROL Current
(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)
MAX. DUTY CYCLE REDUCTION ONSET
THRESHOLD CURRENT vs. TEMPERATURE
PI-2563-033001
Onset Threshold Current
(Normalized to 25 °C)
1.5
00246810
DRAIN Voltage (V)
DRAIN Current (A)
OUTPUT CHARACTERISTICS
PI-1940-033001
0.5
T
CASE
= 25 °C
T
CASE
= 100 °C
1
TOP234 1.00
TOP233 0.67
TOP232 0.33
Scaling Factors:
TOP232-234
B
7/01 33
Typical Performance Characteristics (cont.)
1000
10 0 400200 600
DRAIN Voltage (V)
DRAIN Capacitance (pF)
COSS vs. DRAIN VOLTAGE
100
PI-1941-033001
TOP234 1.00
TOP233 0.67
TOP232 0.33
Scaling Factors:
200
300
100
00 200 400 600
DRAIN Voltage (V)
Power (mW)
DRAIN CAPACITANCE POWER (132 kHz)
PI-1942-033001
TOP234 1.00
TOP233 0.67
TOP232 0.33
Scaling Factors:
TOP232-234
34 B
7/01
PI-2560-033001
Notes:
1. Controlling dimensions are inches. Millimeter
dimensions are shown in parentheses.
2. Pin locations start with Pin 1, and continue
from left to right when viewed from the front.
Pins 2 and 6 are omitted.
3. Dimensions do not include mold flash or
other protrusions. Mold flash or protrusions
shall not exceed .006 (.15mm) on any side.
4. Minimum metal to metal spacing at the pack-
age body for omitted pin locations is .068
inch (1.73 mm).
5. Position of the formed leads to be measured
at the mounting plane, .670 inch (17.02 mm)
below the hole center.
6. All terminals are solder plated.
Y07B
PIN 1 PIN 7
MOUNTING HOLE PATTERN
.050 (1.27)
.150 (3.81)
.050 (1.27)
.150 (3.81)
.050 (1.27)
.050 (1.27)
.180 (4.58)
.200 (5.08)
PIN 1
+
.010 (.25) M
.467 (11.86)
.487 (12.37)
.400 (10.16)
.415 (10.54)
.146 (3.71)
.156 (3.96)
.860 (21.84)
.880 (22.35)
.028 (.71)
.032 (.81)
.050 (1.27) BSC
.150 (3.81) BSC
.108 (2.74) REF
PIN 1 & 7
7° TYP.
PIN 4
.040 (1.02)
.060 (1.52)
.190 (4.83)
.210 (5.33)
.015 (.38)
.020 (.51)
.095 (2.41)
.115 (2.92)
.236 (5.99)
.260 (6.60)
.165 (4.19)
.185 (4.70)
.040 (1.02)
.060 (1.52)
.045 (1.14)
.055 (1.40)
.670 (17.02)
REF.
.570 (14.48)
REF.
TO-220-7B
TOP232-234
B
7/01 35
Notes:
1. Package dimensions conform to JEDEC specification
MS-001-AB (Issue B 7/85) for standard dual-in-line (DIP)
package with .300 inch row spacing.
2. Controlling dimensions are inches. Millimeter sizes are
shown in parentheses.
3. Dimensions shown do not include mold flash or other
protrusions. Mold flash or protrusions shall not exceed
.006 (.15) on any side.
4. Pin locations start with Pin 1, and continue counter-clock-
wise to Pin 8 when viewed from the top. The notch and/or
dimple are aids in locating Pin 1. Pin 6 is omitted.
5. Minimum metal to metal spacing at the package body for
the omitted lead location is .137 inch (3.48 mm).
6. Lead width measured at package body.
7. Lead spacing measured with the leads constrained to be
perpendicular to plane T.
.010 (.25)
.015 (.38)
.300 (7.62) BSC
(NOTE 7)
.300 (7.62)
.390 (9.91)
.375 (9.53)
.385 (9.78)
.245 (6.22)
.255 (6.48)
.128 (3.25)
.132 (3.35)
.057 (1.45)
.063 (1.60)
.125 (3.18)
.135 (3.43)
0.15 (.38)
MINIMUM
.048 (1.22)
.053 (1.35)
.100 (2.54) BSC
.014 (.36)
.022 (.56)
-E-
Pin 1
SEATING
PLANE
-D-
-T-
P08B
DIP-8B
PI-2551-033001
D S .004 (.10)
⊕
T E D S .010 (.25) M
⊕
(NOTE 6)
SMD-8B
PI-2546-040501
.004 (.10)
.012 (.30) .036 (0.91)
.044 (1.12)
.004 (.10) 0 -
°
8
°
.375 (9.53)
.385 (9.78)
.048 (1.22) .009 (.23)
.053 (1.35)
.032 (.81)
.037 (.94)
.128 (3.25)
.132 (3.35)
-D-
Notes:
1. Controlling dimensions are
inches. Millimeter sizes are
shown in parentheses.
2. Dimensions shown do not
include mold flash or other
protrusions. Mold flash or
protrusions shall not exceed
.006 (.15) on any side.
3. Pin locations start with Pin 1,
and continue counter-clock
Pin 8 when viewed from the
top. Pin 6 is omitted.
4. Minimum metal to metal
spacing at the package body
for the omitted lead location
is .137 inch (3.48 mm).
5. Lead width measured at
package body.
6. D and E are referenced
datums on the package
body.
.057 (1.45)
.063 (1.60)
(NOTE 5)
E S
.100 (2.54) (BSC)
.372 (9.45)
.245 (6.22) .388 (9.86)
.255 (6.48) .010 (.25)
-E-
Pin 1
D S .004 (.10)
⊕
⊕
G08B
Heat Sink is 2 oz. Copper
As Big As Possible
.420
.046 .060 .060 .046
.080
Pin 1
.086
.186
.286
Solder Pad Dimensions
TOP232-234
36 B
7/01
Notes
-
1) Corrected rounding of operating frequency (132/66 kHz).
2) Corrected spelling.
3) Corrected Storage Temperature θJC and updated nomenclature in parameter table.
Date
1/00
7/01
Revision
A
B
KOREA
Power Integrations
International Holdings, Inc.
Rm# 402, Handuk Building
649-4 Yeoksam-Dong,
Kangnam-Gu,
Seoul, Korea
Phone: +82-2-568-7520
Fax: +82-2-568-7474
e-mail: koreasales@powerint.com
WORLD HEADQUARTERS
AMERICAS
Power Integrations, Inc.
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
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 PI Logo,
TOPSwitch
,
TinySwitch
and
EcoSmart
are registered trademarks of Power Integrations, Inc.
©Copyright 2001, Power Integrations, Inc.
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.
17F-3, No. 510
Chung Hsiao E. Rd.,
Sec. 5,
Taipei, Taiwan 110, R.O.C.
Phone: +886-2-2727-1221
Fax: +886-2-2727-1223
e-mail: taiwansales@powerint.com
EUROPE & AFRICA
Power Integrations (Europe) Ltd.
Centennial Court
Easthampstead Road
Bracknell
Berkshire, RG12 1YQ
United Kingdom
Phone: +44-1344-462-300
Fax: +44-1344-311-732
e-mail: eurosales@powerint.com
CHINA
Power Integrations
International Holdings, Inc.
Rm# 1705, Bao Hua Bldg.
1016 Hua Qiang Bei Lu
Shenzhen, Guangdong 518031
China
Phone: +86-755-367-5143
Fax: +86-755-377-9610
e-mail: chinasales@powerint.com
INDIA (Technical Support)
Innovatech
#1, 8th Main Road
Vasanthnagar
Bangalore, India 560052
Phone: +91-80-226-6023
Fax: +91-80-228-9727
e-mail: indiasales@powerint.com
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