ZHCSSL6B July 2023 – March 2024 TPS7H6003-SP , TPS7H6013-SP , TPS7H6023-SP
PRODMIX
For proper startup up of the high side, the BOOT to SW voltage must be greater than the BOOT UVLO rising threshold value of 6.65 V (typical). In half-bridge converter configurations that have a pre-bias voltage present at the output, the bootstrap capacitor may not be able to adequately charge from VIN until the output voltage is sufficiently discharged. This same behavior can be seen during a brownout of VIN in which the input voltage temporarily decreases below the VIN UVLO falling threshold. Upon recovery, the low-side driver will attempt to begin normal operation, but the turn-on of the high-side driver will be delayed due to the output voltage that is present on the converter. This is a problem that is inherent in half-bridge gate drivers. Discharge circuits at the converter output can help alleviate the problem by forcing the output to a low voltage, only after which gate drive startup is attempted.