General Description

The MAX1620/MAX1621 convert a 1.8V to 20V battery

voltage to a positive or negative LCD backplane bias

voltage. Backplane bias voltage can be automatically

disabled when the display logic voltage is removed,

protecting the display. These devices use very little PC

board area, come in ultra-small QSOP packages, and

require only small, low-profile external components.

Output voltage can be set to a desired positive or nega-

tive voltage range with external resistors, and adjusted

over that range with the on-board digital-to-analog con-

verter (DAC) or with a potentiometer. The MAX1620/

MAX1621 include a 5-bit DAC, allowing digital software

control of the bias voltage. The MAX1620 uses up/down

digital signaling to adjust the DAC, and the MAX1621

uses the System Management Bus (SMBus™) 2-wire

serial interface.

These devices use a low-cost, external, N-channel MOSFET

power switch or NPN transistor, and can be configured

for positive or negative output voltages. Operating cur-

rent is a low 150µA, typically provided from a display’s

logic supply of 3.0V to 5.5V. The MAX1620/MAX1621 are

available in a 16-pin QSOP package.

Applications

Notebook Computers

Palmtop Computers

Personal Digital Assistants

Portable Data-Collection Terminals

Features

o 1.8V to 20V Battery Input Voltage

o Automatic Disable when Display Logic

is Shut Down

o Extremely Small QSOP Package

o 32-Level Internal DAC

o SMBus Serial Interface (MAX1621)

o Positive or Negative Output Voltage

Digitally Adjustable LCD Bias Supplies

________________________________________________________________

Maxim Integrated Products

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PART

MAX1620EEE

MAX1621EEE

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE

PIN-PACKAGE

16 QSOP

16 QSOP

EVALUATION

KIT MANUAL

FOLLOWS

DATA

SHEET

Ordering Information

19-1214; Rev 1; 1/98

LX

DHI

DLO

PGND

DOUT

FB

POL

SHDN

DN

UP

REF

AGND

MAX1620

12.5V

TO

23.5V OUT

2V TO

12V

3V TO

5.5V

DOWN

UP

LCDON

POK

BATT

Typical Operating Circuit

SMBus is a trademark of Intel Corp.

Pin Configuration

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

DHI

DLO

LX

PGND

AGND

DOUT

FB

DN (SDA)

UP (SCL)

BATT

SHDN (SUS)

POK

REF

POL

LCDON

TOP VIEW

MAX1620

MAX1621

QSOP

( ) ARE FOR MAX1621 ONLY.

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For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 1-800-835-8769.