Overview of Allegro’s A3930 and A3931 Automotive BLDC Controllers
The A3930 and A3931 by Allegro Microsystems Inc. are automotive-focused, 3-phase brushless DC (BLDC) motor controllers designed for use with external N-channel power MOSFETs. They are engineered to facilitate the efficient design of a three-phase motor drive system for automotive applications, aligning with industry requirements for robust performance across a wide input supply range.
Key Features
The controllers offer features vital for automotive systems, including:
- High-current gate driving for N-channel MOSFETs
- Synchronous rectification for improved efficiency
- Protection against cross-conduction
- An integrated charge pump ensuring consistent gate drive voltage
- Integrated commutation decoder logic
- A wide operation range of 5.5 to 50 V supply voltage
- Comprehensive diagnostic outputs
- +5 V power output for Hall sensors
- A low-current sleep mode for energy savings
Specially, the A3930 and A3931 controllers employ a charge pump regulator that delivers more than 10 V gate drive at battery voltages down to 7V and can operate down to 5.5 V. They switch from voltage doubling to dropout mode to save power, using a bootstrap capacitor to generate the necessary above-battery supply voltage.
Performance and Protection
Built-in PWM current control circuitry manages the load current; the peak limit is determined by user-selected reference voltage and an external resistor. PWM input can also adjust speed and torque, leveraging the internal current control to set maximum current limits. Protection features include synchronous rectification to maximize efficiency and crossover control with adjustable dead time to prevent shoot-through.
Physical and Packaging Options
The devices are supplied in a 48-pin LQFP surface mount package with an exposed thermal pad, ensuring efficient heat dissipation. They are available in two main configurations: the A3930 with Hall short detection, and the A3931 with motor pre-positioning suitable for startup algorithms. Trays and reels contain 250 and 1500 pieces, respectively.
Absolute Maximum Ratings
Key parameters outlined in the datasheet include:
- Load Supply Voltage: ~0.3 to 50V
- Operating Temperature Range: -40 to 150°C
- Junction Temperature: 150°C (175°C transient)
- Storage Temperature Range: -55 to 150°C
- ESD protection: 2000V (Human Body Model), 1000V (Charged Device Model)
The A3930 and A3931 controllers differentiate in response to all-zero Hall input states, with the A3930 signaling a logic fault and the A3931 putting motors into a preemptive starting position. The A3931’s feature is particularly beneficial for sensor-less control systems initiated by microprocessors. Compliance with the Automotive Electronics Council’s reliability standards further enhances their applicability in the stringent automotive sector.
References:
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