Relay driver chip for automotive applications

An automotive-grade relay-driver IC provides robust performance over extended voltage and temperature ranges.

The A2550 from Allegro MicroSystems is an automotive-grade relay-driver IC which combines a 5V voltage regulator, watchdog and reset circuitry, and three low-side DMOS relay-driver outputs, providing robust performance over extended voltage and temperature ranges.

The new device is designed to provide key functions in automotive relay-based applications where a microprocessor is used to implement complex system control and requires a logic supply voltage, power-on reset circuitry and watchdog capabilities.

These systems - typically used for the control of wipers, seats, sunroofs and other closure systems - often have an architecture consisting of brush motors controlled very simply by relays driven with simple on/off commands from the control system.

The three low-side DMOS drivers in the A2550 can drive relay coils of up to 250mA each.

Each driver integrates rugged voltage clamps that eliminate the need for external free-wheeling diodes and enable the drivers to survive automotive load dump pulses of up to 48V to ensure adequate survival in harsh automotive environments.

The 5V linear regulator provides 40mA of output current with a tolerance of 2% over the operating temperature range.

To enhance the device's usefulness in automotive applications, the regulator output and the low-side driver outputs are protected against over-current conditions.

The integral power-on reset circuitry and the built-in watchdog circuit combine to service the monitoring and reset requirements of a system microprocessor.

The user can adjust the reset timing and the watchdog timeout by changing the values of two external capacitors.

The A2550 is supplied in a 16-lead TSSOP package with exposed pad.

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