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3.3V/5V Palmtop Computer and LCD Power-Supply Regulator

Battery or Wall Adapter Operated System Power Supply Powers Logic and LCD

Product Details

Key Features

Simplified Block Diagram

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Key Features

  • Low 0.9V to 5.5V Battery Input Range
  • Unregulated 7V to 20V DC Input Range
  • Dual Regulated Outputs
    • Main Output: 3.3V/5V
    • Auxiliary Output: 0V to -100V
  • 87% Efficiency at 200mA
  • Efficient PRAM Keep-Alive: 80% at 1mA
  • 8W/in³ Power Density
  • 60µA Quiescent Current
  • 20µA Shutdown Mode with VREF Alive
  • 500kHz Maximum Switching Frequency
  • ±1.5% VREF Tolerance (Over Temp.)
  • Detect Output Power Failures
  • 16-Pin Narrow SO Packages

Applications/Uses

  • Bar-Code Scanners
  • LCD Contrast Control
  • Medical Instrumentation
  • Palmtop Computers
  • Portable Data Communicators
  • Portable Data-Collection Equipment

Description

The MAX722 and MAX723 CMOS power-supply ICs create dual regulated DC outputs for small, battery-operated microprocessor systems. Each device generates a main output (3V or 5V, selectable) and a negative auxiliary output that is adjustable for LCDs. Each device accepts two input voltages. Power can come from a main battery (two or three alkaline or NiCAD), or an unregulated DC source such as an AC-DC wall adapter.

The MAX722/MAX723 provide three improvements over prior-art devices. Physical size is reduced; the high switching frequencies (up to 0.5MHz), made possible by MOSFET power transistors, allow for tiny (< 5mm diameter) surface-mount magnetics. Efficiency is also improved to 87% (10% better than with low-voltage regulators made in bipolar technology). And supply current is reduced to 60µA by CMOS construction and a unique constant-off-time pulse-frequency modulation (PFM) control scheme.

The MAX722 and MAX723 differ only in the lower fixed output voltage of the main regulator, with a 3.3V output for the MAX722 and a 3.0V output for the MAX723.

For flash memory or PCMCIA applications that require a +12V output voltage, refer to the MAX717–721 data sheet.

Simplified Block Diagram

Technical Docs

Support & Training

Search our knowledge base for answers to your technical questions.

Filtered Search

Our dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .