LX1741CDU - Microsemi Corp.

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

HEET

INTEGRATED PRODUCTS

DESCRIPTION

The LX1741 is a compact high

efficiency step-up boost controller.

Featuring a pseudo-hysteretic pulse

frequency modulation topology, the

LX1741 was designed for maximum

efficiency, reduced board size, and

minimal cost.

Utilizing an external N-Channel

MOSFET, the LX1741 offers

designers maximum flexibility with

respect to efficiency and cost. The

LX1741 provides several design

enhancements that improve overall

performance under very light load

currents by implementing control

circuitry that is optimized for portable

systems - thus providing a quiescent

supply current of only 80µA (typ) and

a shutdown current of less than 1µA.

The input voltage ranges from 1.6V

to 6.0V, allowing for a wide selection

of system battery voltages. Start-up

operation is guaranteed at 1.6V input

The output voltage is programmed

easily using two external resistors in

conjunction with the feedback pin.

Depending on the MOSFET selected,

the LX1741 is capable of achieving

output voltages much higher than 40V.

The LX1741 has an additional feature

for simple dynamic adjustment of the

output voltage (i.e., up to ±15% of the

nominal output voltage). Voltage

adjustment is achieved via an analog

reference signal or a direct PWM input

signal applied to the ADJ pin. Any

PWM amplitude is easily accom-

modated with a single external resistor.

The LX1741 is available in both the 8-

Pin MSOP, and the miniature 8-Pin MLP

requiring minimal PCB area.

IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com

KEY FEATURES

 > 85% Maximum Efficiency

 80µA Typical Quiescent Supply

Current

 Externally Programmable Peak

Inductor Current Limit For

Maximum Efficiency

 Logic Controlled Shutdown

 < 0.5 µA Shutdown Current (typ)

 Dynamic Output Voltage

Adjustment Via Analog Reference

Or Direct PWM Input

 8-Pin MSOP Package or 8-Pin

MLP

APPLICATIONS/BENEFITS

 Pagers

 Wireless Phones

 PDAs

 Handheld Computers

 General LCD Bias Applications

 LED Driver

PRODUCT HIGHLIGHT

4.7µF

1kΩ

47µH

1206 Case Size

BAT

= 1.6V to 6.0V

ON OFF

LCD

= 18V ± 15%

LX1741

GND

SHDN

ADJ

NDRV

SRC

PACKAGE ORDER INFO

LM Plastic MLP

8-Pin DU Plastic MSOP

8-Pin

(°C)

RoHS Compliant / Pb-free

Transition DC: 0452

RoHS Compliant / Pb-free

Transition DC: 0432

0 to 70 LX1741CLM LX1741CDU

Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e.

LX1741CDU-TR)

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

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INTEGRATED PRODUCTS

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (V

) .................................................................................... -0.3V to 7.0V

Feedback Input Voltage (V

) ..............................................................-0.3V to V

+ 0.3V

Shutdown Input Voltage (VSHDN ) ........................................................-0.3V to V

+ 0.3V

PWM Input Amplitude .........................................................................-0.3V to V

+ 0.3V

Analog Adjust Input Voltage (V

ADJ

).................................................................-0.3V to V

Source Input Current (I

SRC

).................................................................................. 0.80 A

RMS

Operating Junction Temperature................................................................................ 150°C

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

Lead Temperature (Soldering 180 seconds)............................................................... 235°C

Peak Package Solder Reflow Temp. (40 seconds max. exposure) ................ 260°C (+0, -5)

Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to

Ground. Currents are positive into, negative out of specified terminal

THERMAL DATA

Plastic MSOP 8-Pin

THERMAL RESISTANCE

JUNCTION TO

MBIENT

206°C/W

THERMAL RESISTANCE

JUNCTION TO

ASE

39°C/W

Plastic MLP 8-Pin

THERMAL RESISTANCE

JUNCTION TO

MBIENT

41°C/W

THERMAL RESISTANCE

JUNCTION TO

ASE

5.2°C/W

Junction Temperature Calculation: T

= T

+ (P

x θ

The θ

numbers are guidelines for the thermal performance of the device/pc-board

system. All of the above assume no ambient airflow.

PACKAGE PIN OUT

SRC

GND IN

NDRV

ADJ SHDN

ACKAGE

(Top View)

8SRC

GND

SHDN

NDRV

ADJ

ACKAGE

(Top View)

RoHS / Pb-free 100% Matte Tin Lead Finish

FUNCTIONAL PIN DESCRIPTION

AME

ESCRIPTION

IN Unregulated IC Supply Voltage Input – Input range from +1.6V to 6.0V. Bypass with a 1µF or greater capacitor

for operation below 2.0V.

FB Feedback Input – Connect to a resistive divider network between the output and GND to set the voltage at V

(see Output Voltage Programming: Application Information).

SHDN

Active-Low Shutdown Input – A logic low shuts down the device and reduces the supply current to 0.1µA.

Connect

SHDN

to V

for normal operation.

NDRV MOSFET Gate Driver – Connects to an external N-Channel MOSFET.

CS Current-Sense Amplifier Input – Connecting a resistor between CS and GND sets the peak inductor current limit.

GND Common terminal for ground reference.

ADJ

An applied PWM Signal Input becomes the internal reference, via an internal filter and gain resistor, thus allowing

for a dynamic output voltage adjustment of ±15% (i.e., corresponding to the duty cycle variance). Connecting this

pin to ground causes the device to revert to the internal voltage reference (note: refer to figure 8).

SRC MOSFET Current Sense Input - Connects to the External N-Channel MOSFET Source.

Microsemi

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LX1741

High Efficiency High Voltage Boost Controller

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INTEGRATED PRODUCTS

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C

≤

70°C except where

otherwise noted and the following test conditions: V

= 3V, V

OUT

= 18.5V, V

ADJ

= 0V, R

LOAD

= 9.25kΩ,

SHDN

= V

LX1741

Parameter Symbol Test Conditions Min Typ Max

Units

Operating Voltage

1.6 6.0 V

Minimum Start-up Voltage

= +25°C 1.6 V

Start-up Voltage Temperature

Coefficient k

VST

-2

mV/°C

= 1.5V 80 100 µA

Quiescent Current

VSHDN

< 0.4V 0.2 0.5

µA

FB Threshold Voltage

ADJ

= GND 1.264 1.290 1.316 V

FB Input Bias Current

= 1.4V -200 200 nA

ADJ Input Voltage Range

ADJ

–

100mV

ADJ Input Bias Current

ADJ

= V

= 1.29V

0.3 1.0

µA

SRC Input Current

SRC

0.8 A

RMS

Shutdown Input Bias Current

ISHDN

SHDN

= GND -50 50 nA

Shutdown High Input Voltage

VSHDN

= 2V 1.6 V

Shutdown Low Input Voltage

VSHDN V

= 2V 0.4 V

Current Sense Bias Current

3.0 5.0 7.0

µA

Minimum Peak Current

MIN

GBNT

145 mA

Comparator A Delay

GBNT

620 ns

NDRV Sink Current

SNK

= 5V 50 mA

NDRV Source Current

SRC

= 5V 100 mA

Minimum Off-Time

OFF

= 1V 100 500 ns

Notes:

1. When using a DC source to adjust V

OUT

, the recommended V

ADJ

(range) is from 0.9V to 1.50V: see figure 3 and 8.

2. Guaranteed typical value (not tested) @ T

= 25

C (see section “Inductor Selection and Current Limit Programming”)

SIMPLIFIED BLOCK DIAGRAM

Logic

Controller

Reference

Logic

ADJ

Shutdown

Logic SHDN

Driver

GND

NDRV

SRC

2.5M

Ω

50pF

1.29V

Reference

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LX1741

High Efficiency High Voltage Boost Controller

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APPLICATION CIRCUITS

Typical LCD Bias Applications

BAT

= (1.6V to 6.0V)

⎟

⎠

⎞

⎜

⎝

⎛+=

REFOUT

1VV

4.7µF

1nF

1kΩ

* Optional Component

used to reduce output

voltage ripple.

47µH

LX1741

NDRV

SHDN

SRC

GND

ADJ

Figure 1 – Fixed Output Voltage Operation

BAT

= (1.6V to 6.0V)

⎟

⎠

⎞

⎜

⎝

⎛+=

ADJOUT

1VV

4.7µF

1nF

1kΩ

* Optional Component

used to reduce output

voltage ripple.

47µH

PWM

100kHz

PWM

= 3.0V

625kΩ

LX1741

NDRV

SHDN

SRC

GND

ADJ

Figure 2 – Dynamic Output Voltage Operation Via PWM Input

Note: An in-series R

PWM

will attenuate the PWM amplitude to the proper signal level at the ADJ pin. With the R

PWM

value

shown, a PWM signal having a duty of 30% to 50% will generate 0.9V to 1.5V at the ADJ pin.

Microsemi

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

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INTEGRATED PRODUCTS

APPLICATION CIRCUITS

(CONTINUED)

Typical LCD Bias Applications (Cont)

BAT

= (1.6V to 6.0V)

⎟

⎠

⎞

⎜

⎝

⎛+=

ADJOUT

1VV

4.7µF

1nF

1kΩ

* Optional Component

used to reduce output

voltage ripple.

47µH

ADJ

= 0.9V to 1.5V +

LX1741

NDRV

SHDN

SRC

GND

ADJ

Figure 3 – Dynamic Output Voltage Operation Via Analog Voltage Input

LED Driver Application

4.7µF

1kΩ

47µH

1206 Case Size

63.4Ω

BAT

= 1.6V to 6.0V

ON OFF

1ΜΩ

59kΩ

= 3.6V typ.

LED

= 20mA to 0.25mA

()

⎟

⎠

⎞

⎜

⎝

⎛⎟

⎠

⎞

⎜

⎝

⎛

−

⎟

⎠

⎞

⎜

⎝

⎛

FADJ

LED

V4V

LX1741

NDRV

SHDN

SRC

GND

ADJ

Figure 4 – LED Driver with Full-Range Dimming Via PWM Input

Note The component values shown are only examples for a working system. Actual values will vary greatly depending on

desired parameters, efficiency, and layout constraints.

Microsemi

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

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INTEGRATED PRODUCTS

APPLICATION CIRCUITS

(CONTINUED)

Rcs

20K

30.9K

47µH

B150/B

50V

1nF

50V

4.7uF

50V

3 x BSS138

Vbat = 3.2V Vout = 40V

LX1741

Figure 5 – Application of Fixed Output, 40V @ 20mA

VBAT +VOUT

4.02K

49.9K

787K

47µH

-VOUT

UPS5819

1uF

25V

1uF

25V

UPS5819

1000pF

50V

1uF

25V

1uF

25V

4.7uF

25V

FDV303N

LX1741

Figure 6 – Application of Dual Output, ± 20V @ 2mA

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

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INTEGRATED PRODUCTS

APPLICATION INFORMATION

UNCTIONAL

ESCRIPTION

The LX1741 is a Pulse Frequency Modulated (PFM)

boost converter that is optimized for large step up voltage

applications like LCD biasing. It operates in a pseudo-

hysteretic mode with a fixed switch “off time” of 300ns.

Converter switching is enabled when the feedback voltage,

, falls below the 1.29V reference or VADJ (see Block

Diagram). When this occurs, comparator A activates the

off-time controller. The off-time controller and the current

limiter circuit activate comparator B which toggles the

NDRV output circuit. The NDRV output is switched “on”

(and remains “on”) until the inductor current ramps up to

the peak current level. This current level is set via the

external R

resistor and monitored through the CS and

SRC inputs.

The load is powered from energy stored in the output

capacitor during the inductor charging cycle. Once the peak

inductor current value is achieved, the NDRV output is

turned off (off-time is typically 300ns) allowing a portion of

the energy stored in the inductor to be delivered to the load.

This causes the output voltage to continue to rise at the

input to the feedback circuit (i.e., comparator A). If the

voltage at the FB input is still less than 1.29V at the end of

the off-time period, the NDRV output switches the external

FET “on” and the inductor charging cycle repeats until V

is greater than the internal reference. This switching

behavior is shown in Figure 9 and 11.

The application of an external voltage source at the ADJ

pin allows for output voltage adjustment over a typical

range of approximately ±15%. The designer can select one

of two possible methods. One option is to vary the

reference voltage directly at the ADJ pin by applying a DC

voltage from 0.9 to 1.5V. The second option is to connect a

PWM logic signal to the ADJ pin (e.g., see Figure 2). The

LX1741 includes an internal 50pF capacitor to ground that

works with an external resistor to create a low-pass filter

(i.e., filter out the AC component of a pulse width

modulated input of f

PWM

≥ 100KHz).

The adjustment voltage level is selectable (with limited

accuracy) by implementing the voltage divider created

between the external series resistor and the internal 2.5MΩ

resistor. If the DC voltage at the ADJ pin drops below

0.6V, the device will revert to the internal reference voltage

level of 1.29V. A typical adjustment curve is shown in

Figure 8 (see section titled: Characteristic Curves).

Disabling the LX1741 is achieved by driving the SHDN pin

with a low-level logic signal thus reducing the device power

consumption to less than 1µA.

UTPUT

OLTAGE

ROGRAMMING

Selecting the appropriate values for R1 and R2 in the

voltage divider connected to the feedback pin programs the

output voltage. Using a value of 49.9K for R2 works well

in most applications. R1 can be determined by the

following equation (where V

REF

= 1.29V nominal):

()

V-V

R2R1

REF

REFOUT

×=

ESIGN

XAMPLE

Let R2 equals 49.9K and the required VOUT equal to

18V.

()

Ω=×Ω= K4.646 49.9KR1 1.29V

1.29V- 18V

NDUCTOR

ELECTION AND

URRENT

IMIT

ROGRAMMING

Setting the level of peak inductor current to, at least, 1.5x

the expected maximum DC input current will minimize the

inductor size, the input ripple current, and the output ripple

voltage. The designer is encouraged to use inductors that

will not saturate at the peak inductor current level. An

inductor value of 47µH is recommended. Choosing a lower

value emphasizes peak current overshoot while choosing a

higher value emphasizes output ripple voltage. The peak

switch current is defined using a resistor placed between the

CS terminal and ground and the I

PEAK

equation is:

SCALE

MINPEAK

RIt

⎟

⎠

⎞

⎜

⎝

⎛

⎟

⎠

⎞

⎜

⎝

⎛

++=

The maximum I

PEAK

value is limited by the I

SRC

value

(max. = 0.8A

RMS

). The minimum I

PEAK

value is defined

when R

is zero. A typical value for the minimum peak

current (I

MIN

) at 25

C is 145mA. The parameter t

is related

to internal operation of comparator A. A typical value at

C is 620ns. A typical value of I

SCALE

at 25

C is 31mA

per KΩ. All of these parameters have an effect on the final

PEAK

value.

ESIGN

XAMPLE

Determine I

PEAK

where V

equals 3.0V and R

equals

4.02KΩ using nominal values for all other parameters.

4.02KΩ

kΩ

31mA

620ns

H47

3.0V

145mAI

PEAK

×+×+=

⎟

⎠

⎞

⎜

⎝

⎛

⎟

⎠

⎞

⎜

⎝

⎛

The result of this example yields a nominal I

PEAK

equal to

145mA + 39.6mA + 124.6ma = 309.2mA.

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

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INTEGRATED PRODUCTS

APPLICATION INFORMATION (CONTINUED)

UTPUT

IPPLE

APACITOR

ELECTION

Output voltage ripple is a function of the inductor value

(L), the output capacitor value (C

OUT

), the peak switch

current setting (I

PEAK

), the load current (I

OUT

), the input

voltage (V

) and the output voltage (V

OUT

) for a this

boost converter regulation scheme. When the switch is

first turned on, the peak-to-peak voltage ripple is a

function of the output droop (as the inductor current

charges to I

PEAK

), the feedback transition error (i.e.,

typically 10mV), and the output overshoot (when the

stored energy in the inductor is delivered to the load at the

end of the charging cycle). Therefore the total ripple

voltage is

RIPPLE

= ∆V

DROOP

+ ∆V

OVERSHOOT

+ 10mV

The initial droop can be estimated as follows where the

0.5v value in the denominator is an estimate of the voltage

drop across the inductor and the FET’s R

DS_ON

()

0.5V

∆V

OUTPK

OUT

DROOP

−

××

⎟

⎠

⎞

⎜

⎝

⎛

The output overshoot can be estimated as follows

where the 0.5 value in the denominator is an estimate of

the voltage drop across the diode:

()

INOUT

OUTPK

OUT

OVERSHOOT

V0.5V

∆V−+

−×

⎟

⎠

⎞

⎜

⎝

⎛

DESIGN EXAMPLE:

Determine the V

RIPPLE

where I

equals 200mA, I

OUT

equals 35mA, L equals 47µH, C

OUT

equals 4.7µF, V

equals 3.0V, and V

OUT

equals 18.0V:

()

mV82

0.53.0

35mA200mA

F4.7

H47

∆V

DROOP

−

××

⎟

⎠

⎞

⎜

⎝

⎛

()

mV4.9

0.30.50.81

mA53mA200

F4.7

H47

∆V

OVERSHOOT =

−+

−×

⎟

⎠

⎞

⎜

⎝

⎛

Therefore, for C

OUT

equals 4.7µF:

RIPPLE

= 28mV + 9.4mV + 10mV = 47.4mV

Increasing the output capacitor value results in the

reduction of the output voltage ripple voltage. Low ESR

capacitors are recommended to reduce ripple caused by the

switching current. Multi-layer ceramic capacitors with

X5R or X7R dielectric are a superior choice featuring small

size, very low ESR, and a temperature stable dielectric.

Low ESR electrolytic capacitors such as solid tantalum or

OS-CON types are also acceptable. Moreover, adding a

capacitor from the output to the feedback pin (C2) allows

the internal feedback circuitry to respond faster which

further minimizes output voltage ripple and reduces noise

coupling into the high impedance feedback input.

IODE

ELECTION

A Schottky diode is recommended for most applications

(e.g. Microsemi UPS5819). The low forward voltage drop

and fast recovery time associated with this device supports

the switching demands associated with this circuit topology.

The designer is encouraged to consider the diode’s average

and peak current ratings with respect to the application’s

output and peak inductor current requirements. Further, the

diode’s reverse breakdown voltage characteristic must be

capable of withstanding a negative voltage transition that is

greater than V

OUT

RANSISTOR

ELECTION

The LX1741 can drive up to 100mA of gate drive

current. An N-channel MOSFET with a relatively low

threshold voltage, low gate charge and low R

DS(ON)

required to optimize overall circuit performance. The

LXE1741 Evaluation Board uses a Fairchild FDV303. This

NMOS device was chosen because it demonstrates an

DS_ON

of 0.33Ω and a total gate charge Q

of 1.64nC (typ.).

PCB

AYOUT

The LX1741 produces high slew-rate voltage and current

waveforms hence; the designer should take this into

consideration when laying out the circuit. Minimizing trace

lengths from the IC to the inductor, transistor, diode, input

and output capacitors, and feedback connection (i.e., pin 6)

are typical considerations. Moreover, the designer should

maximize the DC input and output trace widths to

accommodate peak current levels associated with this

circuit.

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LX1741

High Efficiency High Voltage Boost Controller

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INTEGRATED PRODUCTS

EVALUATION BOARD

VERVIEW

The LXE1741 evaluation board is available from

Microsemi for assessing overall circuit performance. The

evaluation board, shown in Figure 5, is 3 by 3 inches (i.e.,

7.6 X 7.6cm) square and factory calibrated to provide a

nominal 18V output from a 1.6V to 6.0V input. Circuit

designers can easily modify output voltage and current to

suit their particular application by replacing the R1 and R

values respectively. Moreover, inductor, FET, and diodes

are easily swapped out to promote design verification of a

circuit that maximizes efficiency and minimizes cost for any

particular application. The input and output connections are

described in Table 1.

LECTRICAL

ONNECTIONS

Apply the DC input voltage to VBAT (not VCC)

however, the LX1741 IC may be driven from a separate DC

source via the VCC input (if desired). Connect the test load

to VOUT. Primary output voltage adjustment is

accomplished by selecting the appropriate value for R1.

Optional fine adjustment of the output voltage is achieved

by applying either a DC voltage or a PWM-type signal to

the VADJ input. Both low frequency (f < 100KHz) and high

frequency (f > 100KHz) PWM signals are accommodated

by choosing the appropriate jumper connection. Further, the

VADJ circuit can be bypassed by selecting the appropriate

jumper position (see Table 2).

The LX1741 exhibits a low quiescent current (I

< 1µA:

typ) during shutdown mode. The SHDN pin can be used to

examine shutdown performance on the evaluation board.

This pin is pulled-up to VCC via a 10KΩ resistor.

Grounding the SHDN pin shuts down the IC however, the

load is still capable of drawing current through the inductor

& diode circuit path. Hence, V

OUT

during shutdown will be

approximately V

BAT

minus the inductor and diode forward

voltage drop.

The LX1741 can achieve output voltages in excess of

25V. In certain applications, it is necessary to protect the

load from excessive voltage excursions. The evaluation

board provides a VLIM jumper position for this purpose.

Engaging this jumper position ensures that the output

voltage does not exceed 25V.

The LXE1741 evaluation board provides an easy and cost

effective solution for evaluation on the LX1741. The

factory installed component list for the evaluation board is

provided in Table 3 and the schematic is shown in Figure 6.

Figure 7

– LX1741 Circuit Evaluation Board

Table 1: Input and Output Pin Assignments

Name Allowable

Range Description

VBAT 0 to 6V Main power supply for output. (Set external current limit to 0.5A)

VCC 1.6V to 6V LX1741 power. May be strapped to VBAT or use a separate supply if VCC jumper is in the

SEP position. Do not power output from VCC pin on board..

SHDN 0 to VCC Pulled up to VCC on board (10KΩ), Ground to inhibit the LX1741.

VOUT VCC to 25V Programmed for 18V output, adjustable up to 25V.

VADJ IN 0 to VCC Apply a DC input or PWM input to adjust the output voltage.

Note: All pins are referenced to ground.

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

HEET

INTEGRATED PRODUCTS

EVALUATION BOARD (CONTINUED)

Table 2: Jumper Pin Position Assignments

Jumper / Position Function

VCC/ VBAT Use this position when powering VBAT and VCC from the same supply. Do not connect power to the

VCC input when using this jumper position.

VCC/ SEP Use this position when using a separate VCC supply (different from VBAT).

REF/ EXT Use this position when using an external source to adjust the output voltage.

REF/ INT Use this position when using the fixed output voltage mode. In this mode the output voltage can be

varied by changing the value of R1 as described in the data sheet.

ADJ/ HF Use this position when adjusting the output with an external PWM that has a repetition rate in excess of

100KHz.

ADJ/ LF Use this position when adjusting the output with an external PWM that has a repetition rate less than

100KHz. Or when using a DC adjustment voltage.

VLIM/ IN Use this position when adjusting the output voltage to prevent the output voltage from accidentally

exceeding 25V.

VLIM/ OUT This position disables the output voltage adjustment clamp. This position may be desired if maximizing

efficiency when operating near 25V output level.

Note: Always put jumpers in one of the two possible positions

Table 3: Factory Installed Component List for the L X 1741Evaluation Board

Ref Description Supplier Part Number

C1 CAPACITOR, COG, 1000pF, 0402, 50V MURATA GRM36X7R102M050

C2 CAPACITOR, X7R, 0.1uF, 0805, 50V MURATA GRM40X7R104M050

C3 CAPACITOR, Y5V, 2.2uF, 0805, 16V AVX 0805YG225ZAT

C4,5 CAPACITOR, X5R, 4.7uF, 1210, 25V TAIYO YUDEN CETMK325BJ475MN

CR1 RECTIFIER, SCHOTTKY, 1A, 40V,

POWERMITE MICROSEMI UPS5819

L1 INDUCTOR, 47UH, 480mA, SMT TOKO A920CY-470M

JP1-7 3 TERM HEADER, 0.1 IN CTR 3M 929647-09-36-I

SB1-4 JUMPER 3M 929955-06

Q1 MOSFET, N-CHAN, 25V, SOT-23 FAIRCHILD FDV303N

Q2 TRANSISTOR, NPN, 40V, SOT-23 ON MMBT3904LT1

R1 RESISTOR, 698K, 1/16W, 0603 PANASONIC ERJ3EKF6983

R2 RESISTOR, 49.9K, 1/16W, 0603 PANASONIC ERJ3EKF4992

R3 RESISTOR, 619K, 1/16W, 0603 PANASONIC ERJ3EKF6193

R4 RESISTOR, 100K, 1/16W, 0603 PANASONIC ERJ3EKF1003

R5,R6 RESISTOR, 1.00K, 1/16W, 0603 PANASONIC ERJ3EKF1001

R7 RESISTOR, 10.0K, 1/16W, 0603 PANASONIC ERJ3EKF1002

R8 RESISTOR, 4.02K, 1/16W, 0603 PANASONIC ERJ3EKF4021

U1 IC, BOOST CONTROLLER MICROSEMI LX1741

VR1 ZENER, 24V,225mW, SOT-23 ON BZX84C24LT1

Note: The minimum part set for a working power supply consists of: C1, C2, C5, CR1, L1, Q1, R1, R2, R8, U1

Microsemi

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

HEET

INTEGRATED PRODUCTS

EVALUATION BOARD (CONTINUED)

VBAT

GND

VCC

SHDN

VADJ

VOUT

GND

4.7µF

25V

1000pF

50V

4.7µF

25V

0.1µF

50V

2.2µF

16V

10K

4.02K

619K

100K

49.9K

698K

JB1

VCC

JB2

REF

ADJ

JB4

VLIM

MMBT3904LT1

CR1

UPS5819

LX1741

FDV303N

VR1

24V

225mW

BZX84C24LT1

47µH

Figure 8

– LX1741 Boost Evaluation Board Schematic

CHARACTERISTIC CURVES

Channel 1

Channel 2

Figure 9 –

OUT

and Inductor Current Waveforms

Channel 1: V

OUT

(AC coupled; 100mV/div)

Channel 2: Inductor Current (100mA/div.)

Configuration: V

= 1.6V, V

OUT

= 5.0V, I

OUT

= 20.0mA

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7

Adjustment Voltage

Output Voltage

igure 10 –

Typical

OUT

versus V

ADJ

• 0 ~ 0.6V : LX1741 uses internal 1.29V reference.

• 0.7V ~ 0.8V : transition from internal to external reference.

• 0.9 to 1.6V : LX1741 defaults to external voltage reference.

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

HEET

INTEGRATED PRODUCTS

CHARACTERISTIC CURVES

Channel 1

Channel 2

Figure 11

–

OUT

and Inductor Current Waveforms (mA)

Channel 1: V

OUT

(AC coupled; 100mV/div)

Channel 2: Inductor Current (100mA/div.)

Configuration: V

= 3.0V, V

OUT

= 17.9V, I

OUT

= 11.0mA

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 101112131415 1617181920

Output Current

Efficiency (%)

Figure 12 –

Efficiency vs. Output Current (mA)

Configuration: V

= 3.0V, V

OUT

= 17.9V, L1 = 47.0µH

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11121314151617181920

Output Current

Efficiency (%)

Figure 13 –

Efficiency vs. Output Current (mA)

Configuration: V

= 5.2V, V

OUT

= 17.9V, L1 = 94.0µH

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 101112131415 1617181920

Output Current

Efficiency (%)

Figure 14 –

Efficiency vs. Output Current (mA)

Configuration: V

= 3.0V, V

OUT

= 10.0V, L1 = 47.0µH

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

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INTEGRATED PRODUCTS

CHARACTERISTIC CURVES

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11121314151617181920

Output Current

Efficiency (%)

Figure 15 –

Efficiency vs. Output Current (mA)

Configuration: V

= 1.6V, V

OUT

= 5.0V, L1 = 47.0µH

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11121314151617181920

Output Current

Efficiency (%)

Figure 16 –

Efficiency vs. Output Current (mA)

Configuration: V

= 3.0V, V

OUT

= 5.0V, L1 = 47.0µH

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2 0

Output Current

Efficiency (%)

Figure 17 –

Efficiency vs. Output Current (mA)

Configuration: V

= 3.0V, V

OUT

= 5.0V, L1 = 47.0µH

0 20 40 60 80 100 120

Drive Current (mA)

Gate Drive Voltage (V)

Figure 18 – Gate Drive Voltage vs. Drive Current (mA)

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

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INTEGRATED PRODUCTS

PACKAGE DIMENSIONS

8-Pin Miniature Shrink Outline Package (MSOP)

MILLIMETERS INCHES

Dim MIN MAX MIN MAX

A 2.85 3.05 .112 .120

B 2.90 3.10 .114 .122

C – 1.10 – 0.043

D 0.25 0.40 0.009 0.160

G 0.65 BSC 0.025 BSC

H 0.38 0.64 0.015 0.025

J 0.13 0.18 0.005 0.007

K 0.95 BSC 0.037 BSC

L 0.40 0.70 0.016 0.027

M 3° 3°

N 0.05 0.15 0.002 0.006

P 4.75 5.05 0.187 0.198

8-Pin Plastic MLP-Micro Exposed Pad

Internally Connected

together, but isolated

from all other terminals

A2 A

MILLIMETERS INCHES

Dim MIN MAX MIN MAX

A 0.80 1.00 0.031 0.039

A1 0.00 0.05 0.000 0.002

A2 0.65 0.75 0.025 0.029

A3 0.15 0.25 0.005 0.009

b 0.28 0.38 0.011 0.015

D 2.90 3.10 0.114 0.122

E 2.90 3.10 0.114 0.122

e 0.65 BSC 0.025 BSC

D2 1.52 2.08 0.060 0.082

E2 1.02 1.31 0.040 0.052

K 0.20 * 0.008 *

L 0.20 0.60 0.008 0.023

L2 0 0.13 0 0.005

Θ 0° 12° 0° 12°

Note:

1. Dimensions do not include mold flash or

protrusions; these shall not exceed

0.155mm(.006”) on any side. Lead dimension

shall not include solder coverage.

Microsemi

Integrated Products Division

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Rev. 1.1b, 2005-03-03

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LX1741

High Efficiency High Voltage Boost Controller

RODUCTIO N

HEET

INTEGRATED PRODUCTS

NOTES

PRODUCTION DATA – Information contained in this document is proprietary to

Microsemi and is current as of publication date. This document may not be modified in

any way without the express written consent of Microsemi. Product processing does not

necessarily include testing of all parameters. Microsemi reserves the right to change the

configuration and performance of the product and to discontinue product at any time.