Gate Driver controls 3-phase motors.

Press Release Summary:




Model A3938 3-phase power MOSFET controller with high-current gate drive capability, drives discrete n-channel MOSFETs and supports motor supply voltages from 12-50 V. Unit integrates bootstrapped high-side driver, integrated PWM control logic, commutation logic, and synchronous rectification. Offered with selectable coast or dynamic braking options, product includes fixed off-time PWM current control circuitry and adjustable crossover delay.



Original Press Release:



New High-Current Gate Driver for Three-Phase Motors



Integrated Solution Drives a Wide Range of High Power N-Channel MOSFETs and includes Power Loss Brake Function

Worcester, MA - March 20, 2003 - Allegro MicroSystems, Inc. introduces a new three-phase power MOSFET controller with high-current gate drive capability that drives a wide range of power discrete n-channel MOSFETs and supports motor supply voltages from 12 V to 50 V. The A3938 integrates a bootstrapped high-side driver to minimize the external component count required to drive the n-channel MOSFETs. Integrated PWM control logic, commutation logic, synchronous rectification and sophisticated protection features make the A3938 cost-effective and easy to implement. The A3938 offers selectable coast or dynamic braking options, allowing the end user controlled motor operation during a power loss event.

Internal fixed off-time PWM current control circuitry can be used to regulate the maximum load current to a desired value for speed/torque control. For added flexibility, a user-selected external RC timing network sets the fixed off-time pulse duration. In addition, the A3938 features an adjustable crossover delay for cross conduction protection.

The A3938 synchronous rectification circuitry minimizes the power dissipation in the discrete MOSFETs, eliminating the need for external power clamp diodes and allows for a more economical choice for the n-channel MOSFET drivers.

Allegro's A3938 also provides commutation logic to directly interface Hall sensors configured for 120-degree spacing. The Hall input pins are pulled up to an internally generated 5 V reference. Power MOSFET protection features include a bootstrap capacitor charging current monitor, an under-voltage monitor, a motor lead short-to-ground, and thermal shutdown.

The A3938 is manufactured using Allegro's new ABCD3 (Allegro Bipolar CMOS DMOS 3rd generation) process, and is targeted to meet the needs of the office automation, industrial, consumer and medical equipment markets. The A3938 is offered in the following packages: 32-lead PLCC, 36-lead QSOP package, and a 38-lead TSSOP. All packages have a 14 - 16 week lead-time to market, and are priced at $3.11 per part in quantities of 10,000.

Allegro MicroSystems, Inc. is a leading supplier of advanced mixed-signal power semiconductors and Hall-effect sensors targeted toward the computer/office, automotive, industrial, telecommunication and consumer markets. With over 2,400 employees, Allegro is headquartered in Worcester, MA and operates multiple wafer-fabrication plants worldwide. Further information on Allegro can be found at www.allegromicro.com.

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