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MAX749
Digitally Adjustable LCD Bias Supply

Capable for generating >-100V


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Description
FULL DATA SHEET (PDF, 120kB)
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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, simplifying software control. The MAX749 drives either an external P-channel MOSFET or a PNP transistor.

Key Features   Applications/Uses
  • +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

 
  • Communication Systems
  • Laptop Computers
  • Notebook Computers
  • Palmtop Computers
  • PDAs and Other Handheld Devices
  • Portable Data-Collection Terminals

    Key Specifications:   Switch-Mode DC-DC Power Supplies
    Part Number Topology VIN (min) (V) VIN (max) (V) Number of DC-DC Outputs Digital/VID Programmed Output Min. Adjustable VOUT (V) Max. Adjustable VOUT (V) IOUT (A) Operating Current, ICC (max) (mA) Fixed Freq/PWM Operation Operating Freq. (kHz) Internal Power Switch(es) Synchronous Rectifier Package Smallest Available Package (max w/pins) (mm2) Price**
    MAX749  Inverting 2 6 1 No -2 -100 0.1 0.06 Yes 500 No No DICE SALES/0
    PDIP/8
    SOIC/8
    31 $2.49 @ 1k
    See All Switch-Mode DC-DC Power Supplies (421)
    Notes:
    **This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

    Diagram
    MAX749: Typical Operating Circuit
    Typical Operating Circuit

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    Document Ref.: 19-0143; Rev 1; 1995-02-01
    This page last modified: 2007-07-17



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