STMicro introduces hot swap ideal diode controller for functional safety
The STPM801 is the industry’s hot swap and ideal-diode controller certified for automotive safety critical applications up to ASIL-D, claimed STMicroelectronics. The automotive-qualified device integrates an ideal diode controller which drives an external MOSFET replacing a Schottky diode conventionally used for reverse input protection and output voltage holdup. The reduced voltage drop across the MOSFET reduces power dissipation during normal operation, explained ST, compared to the forward voltage of the Schottky diode. When a reverse voltage event occurs, in case of faults like power source failure, brownout or input short circuit, turning off the MOSFET blocks the associated reverse current transients.
The ideal diode controller circuit also provides power ORing, to switch between a main and backup battery to ensure uninterrupted supply to safety critical equipment such as autonomous driving and advanced driver assistance systems (ADAS).
The integrated hot-swap controller drives a second external N-channel MOSFET to protect loads during hot swap events. A soft start function controls the turn on transient of this second MOSFET by charging a capacitor of known value connected to its gate at constant current to avoid high inrush currents. The over voltage and under voltage pins cut off the output voltage whenever the input voltage is not within specified thresholds.
The STPM801 also includes protection features and monitoring suitable for applications that meet functional safety requirements for systems up to Automotive Safety Integrity Level (ASIL) D according to ISO 26262. All of this functionality is packaged in a 5.0 x 5.0mm VFQFN-32 footprint. According to ST, this save PCB space and minimises the external component count.
The controller operates from a supply voltage of 4.0 to 65V and a quiescent current of 25 microA in order for the STPM801 to withstand automotive electrical hazards and minimises battery drain when the vehicle is turned off. It is used in zonal/body engine control units (ECUs), ADAS ECUs, high-performance computing ECUs, infotainment ECUs, redundant power delivery systems and dual-battery systems.
The STPM801 is in mass production now.
