19-1214; Rev 1; 1/98
Dig it a lly Ad ju s t a b le LCD Bia s S u p p lie s
0/MAX621
Ge n e ra l De s c rip t io n
Fe a t u re s
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.
♦ 1.8V to 20V Battery Input Voltage
♦ Automatic Disable when Display Logic
is Shut Down
♦ Extremely Small QSOP Package
♦ 32-Level Internal DAC
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.
♦ SMBus Serial Interface (MAX1621)
♦ Positive or Negative Output Voltage
Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
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.
MAX1620EEE
MAX1621EEE
16 QSOP
Ap p lic a t io n s
Notebook Computers
Palmtop Computers
Typ ic a l Op e ra t in g Circ u it
Personal Digital Assistants
Portable Data-Collection Terminals
2V TO
12V
P in Co n fig u ra t io n
BATT
12.5V
TO
23.5V OUT
3V TO
5.5V
V
LX
DHI
DD
TOP VIEW
POL
DN (SDA)
UP (SCL)
BATT
1
2
3
4
5
6
7
8
16 DHI
DLO
/
ON OFF
SHDN
DLO
15
DOWN
UP
DN
UP
14 LX
PGND
SHDN (SUS)
POK
13 PGND
MAX1620
MAX1621
MAX1620
REF
12
11
10
9
AGND
DOUT
REF
V
DD
FB
POL
DOUT
FB
AGND
LCDON
POK LCDON
QSOP
( ) ARE FOR MAX1621 ONLY.
SMBus is a trademark of Intel Corp.
________________________________________________________________ Maxim Integrated Products
1
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.