JAJSMF5B september 2022 – june 2023 TPS25990
PRODUCTION DATA
The TPS25990 can detect and report certain conditions which are indicative of a failure of the power path FET. If undetected or unreported, these conditions can compromise system performance either by not providing power to the load correctly or the necessary level of protection. After a FET failure is detected, the TPS25990 tries to turn off the internal FET by pulling the gate low and asserts the FLT pin. The specific FET fault type is also reported in the STATUS_MFR_SPECIFIC status register.
D-S short: D-S short can result in a constant uncontrolled power delivery path formed from source to load, either due to a board assembly defect or due to internal FET failure. This condition is detected at start-up by checking if VIN-OUT < VDSFLT before the FET is turned ON. If yes, the device engages the internal output discharge to try and discharge the output. If the VOUT doesn’t discharge below VFB within a certain allowed interval, the device asserts the FLT pin and sets the FET_FAULT_DS bit in the STATUS_MFR_SPECIFIC status register.
There is an option to disable the D-S fault detection digitally by setting the DIS_VDSFLT bit in the DEVICE_CONFIG register. This allows the device start-up into a pre-charged output without triggering the D-S fault.
G-D short: The TPS25990 detects this kind of FET failure at all times by checking if the gate voltage is close to VIN even when the internal control logic is trying to hold the FET in OFF condition. If this condition is detected, the device asserts the FLT pin and sets the FET_FAULT_GD bit in the STATUS_MFR_SPECIFIC status register.
G-S short: The TPS25990 detects this kind of FET failure during start-up by checking if the FET G-S voltage fails to reach the necessary overdrive voltage within a certain timeout period (tSU_TMR) after the gate driver is turned ON. While in steady-state, if the G-S voltage becomes low before the controller logic has signaled to the gate driver to turn off the FET, it is latched as a fault. If this condition is detected, the device asserts the FLT pin and sets the FET_FAULT_GS bit in the STATUS_MFR_SPECIFIC status register.