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Allegro MOSFET pre-driver controls dc brush motors

Posted: 06 May 2003 ?? ?Print Version ?Bookmark and Share

Keywords:allegro microsystems? a3940? pre driver ic? power mosfet driver? dc motor driver?

The A3940 power MOSFET pre-driver IC of Allegro MicroSystems Inc. provides four high-current, gate-drive outputs capable of driving a wide range of power n-channel MOSFETs and is designed for use in large brush dc motors found in the automotive and industrial markets.

Available as a 28-lead TSSOP or SOIC, the device operates bipolar stepper motors in full, half, quarter, and eighth step modes, with output drive capability of 30V and 750mA.

Bootstrap capacitors are used to provide the above-battery supply voltage required for n-channel FETs, while an internal charge pump for high side allows for dc operation of the bridge. PHASE and ENABLE input terminals are provided for use in controlling the speed and direction of a dc motor with externally applied PWM control signals.

When a STEP signal occurs, the A3967 determines if that step results in a higher or lower current in each of the motor phases. If the change is a higher current, then the decay mode is set to slow decay. If the change is a lower current, then the decay mode will be set by the voltage at the percent-fast-decay input.

The A3940 is manufactured using the Allegro Bipolar CMOS DMOS 3rd generation (ABCD3) process and carries protection features including supply undervoltage and overvoltage, programmable dead time adjustment for cross-conduction protection, thermal shutdown, and motor lead short-to-supply and short-to-ground protection.

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