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Allegro MicroSystems, Inc. Announces Half-Bridge
Pre-Driver IC Targeted at High-Power Automotive and Industrial Loads
New Gate-Driver IC (A3946) 
Worcester, MA - July 25, 2003 — Allegro MicroSystems, Inc. announces the release of the A3946, a new power-MOSFET pre-driver IC designed to drive brush DC motors, three-phase brushless DC motors (BLDC), switched reluctance motors, and other large inductive loads. With features such as fault reporting, extended operating voltages (7 V to 60 V), and extended temperature ratings (-40°C to +135°C), the A3946 becomes a perfect choice for driving automotive loads.
The A3946 provides two high-current gate-drive outputs capable of driving a wide variety of N-Channel MOSFETs. The two outputs are configured to drive a classic half-bridge. An externally supplied PWM signal to the input of the A3946 switches the high-side gate-driver output. The low-side gate-driver output can be configured to automatically switch on during the PWM off-time, thereby acting as a synchronous rectifier.
A unique feature of the A3946 is the flexibility of the two inputs. These can either be tied together to allow for a single PWM input signal, or they can be driven independently to provide direct control over the high-side and low-side gate drive outputs. In the single PWM input mode the cross-conduction dead time is determined by the value of an external resistor. When driving the two inputs independently, the system controller determines the cross-conduction dead time.
A bootstrap capacitor is utilized to provide the above-battery supply voltage required for N-Channel MOSFETs. An internal charge pump for the high side will allow for DC (100% duty cycle) operation of the half bridge.
The A3946 is manufactured using Allegro's ABCD3 (Allegro Bipolar CMOS DMOS 3rd generation) process, and is supplied in a batwing 16-lead SOIC. This half-bridge pre-driver IC is targeted to meet the needs of the automotive and industrial markets.
About Allegro
Allegro MicroSystems, Inc. is a leader in developing, manufacturing and marketing high-performance power and Hall-effect sensor integrated circuits. Allegro's innovative solutions serve high-growth applications within the automotive, communications, computer/office automation, consumer and industrial markets. Allegro is headquartered in Worcester, Massachusetts (USA) with design and applications centers located in North and South America, Asia, and Europe. Further information about Allegro can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director - Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com
Technical Contact:
Bob Brodeur
Strategic Marketing Manager
Tel: (508) 854-5558
bbrodeur@allegromicro.com