Full-bridge gate drivers shrink system size

Allegro MicroSystems, Inc. has launched two new full-bridge gate drivers for automotive and industrial applications that can replace mechanical relays with solid-state drivers to improve performance and reliability. The A89505 with direct control and the A89506 with pulse-width modulation options provide a range of built-in capabilities including flexible interface logic, EMI mitigation with programmable gate drive, motor current feedback, and diagnostic features, requiring fewer external components. In addition, the gate drivers are available in a 4 × 4-mm QFN package, which is 36% smaller than comparable  5 × 5-mm devices.

A89505 and A89506 full-bridge gate drivers. Click for a larger image. (Source: Allegro MicroSystems)

Both the A89505 and A89506 full-bridge gate drivers include built-in current sensing capabilities, which eliminate the need for external current sense resistors and reduce external component requirements to as few as seven, reported Allegro. The integrated diagnostics also eliminate the need for additional microprocessor programming and circuitry.

The gate drivers are suited for vehicle applications such as window and door actuators, electric-vehicle charger locks, electronic parking brakes, and folding mirrors. In addition, the solid-state design makes them suited for battery-powered applications that use brushed DC motors such as building automation and robotics.

The A89505 and A89506 are capable of 50-V absolute maximum supply voltages and offer higher gate drive voltage at low VBB and better efficiency when running on battery power, which allows designers to specify lower-cost FETs, said Allegro. They also enable lower current draw in standby states to reduce total battery load.

Other features include a programmable gate drive that reduces EMI and transients caused by fast switching and current limit detection flags that are triggered when the programmable current limit is reached. The current limit detection flags allow a vehicle’s electronic control unit (ECU) to detect pinches or stalls, with the ability to overdrive a motor in case of ice or freezing, said Allegro. Both drivers can adjust gate current to better control the slew rate of external MOSFETs, added the company.

A89505 functional block diagram. Click for a larger image. (Source: Allegro MicroSystems)

“In addition to being 36% smaller than other drivers on the market, the A89505 and A89506 include advanced features and capabilities that help designers shrink overall PCB sizes and fit everything into more compact modules,” said Steve Lutz, business line director for motor drivers at Allegro, in a statement. Both drivers are easier to use and implement than relays or discrete systems, and increase overall reliability while reducing power consumption.”

The A89505 and A89506 are available in a 4 × 4 mm, 20-contact QFN package (suffix “ES”) and a 20-lead eTSSOP (suffix “LP”), both with exposed thermal pad. Contact an Allegro sales office or authorized distributor for product pricing and samples.