Rainbow Electronics MAX749 - Manual

Digitally Adjustable LCD Bias Supply
_______________General Description
The MAX749 generates negative LCD-bias contrast
voltages from 2V to 6V inputs. Full-scale output voltage
can be scaled to -100V or greater, and is digitally
adjustable in 64 equal steps by an internal digital-to-
analog converter (DAC). Only seven small surface-
mount components are required to build a complete
supply. The output voltage can also be adjusted using
a PWM signal or a potentiometer.
A unique current-limited control scheme reduces supply
current and maximizes efficiency, while a high switching
frequency (up to 500kHz) minimizes the size of external
components. Quiescent current is only 60µA max and is
reduced to under 15µA in shutdown mode. While shut
down, the MAX749 retains the voltage set point, simpli-
fying software control. The MAX749 drives either an
external P-channel MOSFET or a PNP transistor.
________________________Applications
Notebook Computers
Laptop Computers
Palmtop Computers
Personal Digital Assistants
Communicating Computers
Portable Data-Collection Terminals
____________________________Features
♦ +2.0V to +6.0V Input Voltage Range
♦ Flexible Control of Output Voltage:
Digital Control
Potentiometer Adjustment
PWM Control
♦ Output Voltage Range Set by One Resistor
♦ Low, 60µA Max Quiescent Current
♦ 15µA Max Shutdown Mode
♦ Small Size – 8-Pin SO and Plastic DIP Packages
MAX749
_______________________________________________________________ Maxim Integrated Products 1
1
2
3
4
8
7
6
5
CS
DHI
DLOW
GND FB
CTRL
ADJ
V+
DIP/SO
TOP VIEW
MAX749
__________________Pin Configuration
V+
ADJ
CTRL
FB
CS
DHI
DLOW
GND
V IN +5V
-V OUT
R SENSE
C COMP
ON/OFF
DIGITAL
ADJUST
R FB
1 0.1 µ F
2
3
4 5
6
7
8
MAX749
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.
19-0143; Rev 1; 2/95
PART TEMP. RANGE PIN-PACKAGE
MAX749CPA 0°C to +70°C 8 Plastic DIP
MAX749CSA 0°C to +70°C 8 SO
MAX749EPA -40°C to +85°C 8 Plastic DIP
MAX749ESA -40°C to +85°C 8 SO
MAX749C/D 0°C to +70°C Dice*
______________Ordering Information
* Contact factory for dice specifications.
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