Isolated Transformer Driver for PCMCIA Applications

Internal Power MOSFETs Save Space and Deliver 750mW
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Status Explanations for product status codes

Active: In Production.


The MAX845 provides an isolated power supply small enough to fit in thin PCMCIA cards and space-sensitive applications. It drives a low-profile center-tapped transformer primary from a 5V or 3.3V DC power supply. The secondary can be wound to provide any isolated positive or negative voltage at powers up to 750mW.

The MAX845 consists of an oscillator followed by a toggle flip-flop. The flip-flop generates two 50% duty-cycle square waves, which are complementary at half the oscillator frequency (450kHz, min). These two signals drive the ground-referenced N-channel power switches. Internal circuitry ensures break-before-make action between the two switches.

A low-power shutdown disables both the switches and the oscillator, reducing power consumption. An evaluation kit (MAX845EVKIT-MM) is available to evaluate low-profile 5V 40mA and 5V 100mA applications.

Data Sheet

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An evaluation board is available: MAX845EVKIT

Key Features

  • Transformer Driver for Ultra-Thin 5V-µs Transformers
  • Isolated DC-to-DC Power Supply for PCMCIA Applications
  • 450kHz Minimum Switching Frequency
  • Ultra-Low Input Supply Current Ripple
  • Single +5V or +3.3V Supply
  • 5µW Low-Power Shutdown Mode
  • 8-Pin SO and µMAX Packages
  • Low Output Ripple Permits Miniature Output Capacitors


  • Bridge Ground Differentials
  • Isolated Data Acquisition
  • Isolated Interface Power Supply
  • Low-Power LAN Networks
  • Medical Equipment
  • Noise-Immunity Communications Interface
  • PCMCIA Modem Cards
  • Process Control

Key Specifications:

Transformer Drivers
Part Number VIN
Driver Output Resistance
Topology Features Freq.
Oper. Temp.
min max max See Notes
MAX845  2.5 6 4 0.2 Push-Pull
Thermal Shutdown
860 1.1 -40 to +85 $2.23 @1k
See All Transformer Drivers (6)

Pricing 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 and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.


MAX845: Typical Operating Circuit
Typical Operating Circuit

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Information Index

Document Ref.: 19-0372 Rev 4; 1997-10-01
This page last modified: 2007-05-30