Three-phase isolator MOSFET driver IC is designed to replace relays
Published time: 2018-12-20
Three-phase isolator MOSFET driver replaces relays-Allegro A6861
Allegro MicroSystems, LLC (Worcester, MA) introduced a new N-channel power MOSFET driver capable of isolating a three phase load by controlling the in-phase isolation MOSFETS. Allegro’s A6861 motor driver IC is intended for automotive systems that must meet Automotive Safety Integrity Level (ASIL) requirements.
The A6861 has three independent floating gate drive outputs to maintain the power MOSFETs in the on state, or the off state, over the full supply range in the presence of high phase-voltage slew rates. With the addition of a few external components it can also isolate the load when high load currents are present. An integrated charge pump regulator provides the above battery supply voltage necessary to maintain the power MOSFETs in the on state continuously when the phase voltage is equal to the battery voltage. The charge pump will maintain sufficient gate drive (>7.5 V) for battery voltages down to 4.5 V with 100 kΩ gate-source resistors. The three gate drives can be independently controlled by a logic level control input. Key applications include:
- EPS (Electronic Power Steering) systems.
- Electric braking.
- Three-phase relay drivers.
Three-phase isolator MOSFET driver replaces relays-Allegro A6862
With the A6862, Allegro Microsystems Europe has introduced an n-channel MOSFET driver IC that can isolate a three-phase load by directly driving the isolation MOSFET, separately phase by phase. The device is designed for safety-relevant automotive systems that need to fulfill the ASIL requirements. Examples are electronic power steering, applications with three-phase relay drivers and electric brakes.
In safety-critical applications, motor isolation is a requirement which in most cases is met by discrete circuits or mechanical relays. Allegro’s A 2-SIL products offer a beneficial alternative and ease ASIL certification. The A6862 3-phase isolating driver can replace relay-controlled motor cut-off in safety-critical systems. Likewise, it can be used as reverse polarity protection and as battery separating switch.
The A6862 has three independent floating gate driver ports which enables the power MOSFETS to retain in the on- or off-state across the entire supply voltage range as well as under high phase voltage gradients. Representing The third generation of isolating drivers from Allegro, the A6862 is now equipped with additional single-input control mode, two independent enabling inputs to switch the device to energy saving mode and additional gate-source protection. The chip comes in a 16-pin TSSOP package with Exposed Pad for better heat removal.
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