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MAX1620, MAX1621
Digitally Adjustable LCD Bias Supplies

Industry's-First Digitally Controlled Positive or Negative LCD Bias Supply


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Description
FULL DATA SHEET (PDF, 264kB)
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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 negative voltage range with external resistors, and adjusted over that range with the on-board digital-to-analog converter (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 current 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.

Key Features   Applications/Uses
  • 1.8V to 20V Battery Input Voltage
  • Automatic Disable when Display Logic is Shut Down
  • Extremely Small QSOP Package
  • 32-Level Internal DAC
  • SMBus Serial Interface (MAX1621)
  • Positive or Negative Output Voltage

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

    Key Specifications:   Inverting Switching Regulators
    Part Number VIN (min) (V) VIN (max) (V) IOUT (A) IOUT (A) Output Adj. Method Operating Current, ICC (max) (mA) Number of DC-DC Outputs Alternate Topology Operating Freq. (kHz) Package Price**
    MAX1620  1.8 20 0.07 0.07 Digital
    Resistor
    0.25 1 Inverting
    Step-Up
    300 QSOP/16 $1.99 @ 1k
    MAX1621   
    See All Inverting Switching Regulators (21)

    Key Specifications:   Step-Up Switching Regulators
    Part Number VIN (min) (V) VIN (max) (V) IOUT (A) IOUT (A) Output Adj. Method Operating Current, ICC (max) (mA) Number of DC-DC Outputs Operating Freq. (kHz) Package Price**
    MAX1620  1.8 20 0.07 0.07 Digital
    Resistor
    0.25 1 300 QSOP/16 $1.99 @ 1k
    MAX1621   
    See All Step-Up Switching Regulators (89)
    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
    MAX1620, MAX1621: Typical Operating Circuit
    Typical Operating Circuit

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    Document Ref.: 19-1214; Rev 1; 1998-01-01
    This page last modified: 2007-07-17



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