Microsemi

Integrated Products Division

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

Page 9

Copyright

 2000

Rev. 1.1, 2002-11-21

LX1741

High Efficiency High Voltage Boost Controller

I N T E GR A T ED

PRO DUC T S

EVALUATION BOA RD

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

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.

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).

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 10K

Ω resistor.

Grounding the SHDN pin shuts down the IC however, the

load is still capable of drawing current through the inductor

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

Pin

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.