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Allegro three-phase driver IC targets factory automation apps

Posted: 04 Nov 2002 ?? ?Print Version ?Bookmark and Share

Keywords:allegro microsystems? a3935? mosfet controller? automotive mosfet? power mosfet controller?

Allegro Microsystems Inc. calls its A3935 automotive power MOSFET controller a substantially integrated pre-driver IC for large three-phase brushless dc motors that brings operating and monitoring flexibility to factory automation and under-the-hood automotive environments. The device targets such applications such as engine cooling and electronic power steering.

The A3935's six outputs (three high-side, three low-side driver blocks) can drive a wide range of external n-channel power MOSFETs serving in the motor's three-phase bridge.

This gate-drive IC, using the company's bipolar CMOS DMOS process, called ABCD3, operates from a 7V to 40V input, making it a good choice for systems where either 12V or 24V battery systems are in use. It integrates a pulse-frequency-modulated boost converter and an LDO regulator that allows the chip to maintain adequate gate drive voltage under low-battery conditions or when used with a low-voltage supply.

The device has six TTL-compatible parallel-input pins, allowing the user to directly and independently control each of the external power MOSFETs used in the application. Thus, the user can implement functions like sinusoidal control of the brushless dc motor. A differential amplifier is included in the circuitry to accurately measure the current in the three-phase bridge.

The chip's protection circuitry has an adjustable overvoltage setting, which protects the IC if the motor's supply voltages exceed a user-set voltage (range is 19.4V to 40V). Additional protection features include circuitry for undervoltage and thermal shutdown.

Tied in with those protection features are several functions that are particularly useful in automotive and industrial applications, including fault reporting and diagnostics for short-to-battery, short-to-supply, and bridge-open conditions. Three fault-output reporting pins are used to help a system controller diagnose and decode the cause of a fault and to take appropriate action.

The A3935, in a 36-lead QSOP, is rated for operation over -400C to 1350C ambient. It is priced at $3.26 each in quantities of 10,000. Lead time is eight weeks.

EE Times

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