The L99MH98 has been designed to drive four external full bridges, eight half bridges or single high-side/low-side powering mechanisms such as seat-position adjusters, window lifters, sunroofs, pumps, seatbelt pretensioners, and other actuators. It can also drive resistive loads such as heaters, and the internal circuitry contains a charge pump whose output can control a reverse-battery protection MOSFET.
While the drivers can control both logic-level and standard-level MOSFETs, extended gate current capability, programmable up to 120mA, permits driving large numbers of external MOSFETs. Three-stage gate control, which applies the gate signal in three steps, helps to minimize electromagnetic emissions.
Designed to provide each MOSFET’s drain-source voltage (VDS) to an analogue-digital converter (ADC), the L99MH98 leverages indirect current measurement to replace sensing resistors. This ST-patented technique calculates the drain current in each MOSFET by combining the measured VDS with RDS(on) predicted using sensed temperature. The system is calibrated at manufacture to find the nominal RDS(on) values, enabling predictions to be made using the MOSFETs’ resistance-versus-temperature curves.
Another feature, also ST-patented, is the programmable multi-failsafe function that enhances reliability by turning off bridges individually to protect against faults while allowing unaffected bridges to operate normally. Multi-failsafe detects faults including supply overvoltage, high-side over/undervoltage, thermal warning, charge-pump failure, VDS-monitoring failure, and selectively turns off functions such as diagnostics, watchdog, and charge pump depending on fault type.
The L99MH98 is AEC-Q100 qualified and meets ISO 26262 criteria for functional-safety applications up to safety integrity level (ASIL) B.
