Isolated Transformer Driver for PCMCIA Applications

 

Part Number	Replacement	Explanation

Description

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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.

MAX845: Typical Operating Circuit Enlarge+

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

Applications/Uses

• 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