MAX1620 Datasheet, PDF (1/20 Pages) Maxim Integrated Products – Digitally Adjustable LCD Bias Supplies

19-1214; Rev 1; 1/98
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Digitally Adjustable LCD Bias Supplies
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.
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
PART
MAX1620EEE
MAX1621EEE
Ordering Information
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
Applications
Notebook Computers
Palmtop Computers
Personal Digital Assistants
Portable Data-Collection Terminals
Pin Configuration
TOP VIEW
DN (SDA) 1
UP (SCL) 2
BATT 3
SHDN (SUS) 4
POK 5
REF 6
POL 7
LCDON 8
MAX1620
MAX1621
( ) ARE FOR MAX1621 ONLY.
QSOP
16 DHI
15 DLO
14 LX
13 PGND
12 AGND
11 V_DD
10 DOUT
9 FB
Typical Operating Circuit
2V TO
12V
3V TO
5.5V
ON/OFF
DOWN
UP
BATT
V_DD
LX
POL
DHI
SHDN
DN
UP
DLO
PGND
MAX1620
REF DOUT
AGND
FB
POK LCDON
12.5V
TO
23.5V OUT
SMBus is a trademark of Intel Corp.
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