PCIM: Functional safety isolated gate driver for SiC and IGBT vehicle traction inverters

Texas Instruments is aiming at electric vehicle traction inverters with a functional safety-compliant isolated gate driver for silicon carbide mosfets and IGBTs.

Called UCC5880-Q1, it is in pre-production and the full data sheet has not yet been made public.

One novel feature that has been revealed is that the device has two parallel high-side drivers and two parallel low-side drivers for the following gate.

In each case, one driver of a pair can deliver up to 5A and the other up to 15A.

These can be enabled and disabled on-the-fly to vary drive across 5A – 15A – 20A.

Each of the four outputs is via a separate pin, allowing four separate slew-limiting series resistors to be applied.

Variable drive has been included for transient over-shoot management at the driven device’s output node. “A fully charged battery with a state of charge from 100% to 80% should use low gate-drive strength to maintain SiC voltage overshoot within the limits,” said TI’s George Lakkas. “As the battery charge drops from 80% to 20%, employing high gate-drive strength reduces switching losses and increases traction inverter efficiency. These scenarios are possible during 75% of the charging cycle, so the efficiency gains can be quite significant.”

Power transistor protections include shunt resistor based over-current, over-temperature and desaturation detection, and there is selectable soft turn-off or two-level soft turn-off as a response to these faults.

An active Miller clamp is included, as is an active gate pull-down while the driver is un-powered.

A 10bit ADC enables monitoring of up to two analogue inputs, the secondary side supply voltage, desat and the driver’s temperature. This part of a suite of built-in self-test circuits.

“Diagnostics and detection functions are integrated to simplify the design of ASIL-compliant systems,” according to TI. “The parameters and thresholds for these features are configurable
using the SPI interface, which allows the device to be used with nearly any SiC mosfet or IGBT.”

Documentation will be available to aid ISO 26262 system design up to ASIL D

Common-mode transients up to 100kV/µs are allowed across the isolation barrier, and 5kVrms isolation testing for 1 minute as per UL1577 is in the pipeline.

Packaging is 10.5 x 7.5mm 32pad SSOP.

With SiC mosfet maker Wolfspeed, TI has created TIDM-02014, an example 800V SiC traction inverter for motor sup to 300kW and 20,000rpm.