7.3.11.2 Low-Side Overcurrent Protection

The conduction current of the low-side MOSFET is also monitored by TPS54678. During normal operation, the low-side sources current into the load. When the sourcing current reaches the internally set low-side sourcing (forward) current limit, the high-side is not turned on and skipped during the next clock cycle. Under this condition, the low-side is kept on until the sourcing current becomes less than the internally set current limit and then the high-side is turned on at the beginning of the following clock cycle. This ensures protection under an output short condition; thereby, preventing current run-away.

The low-side can also sink current from the load. If the low-side sinking (reverse) current limit is exceeded, the low-side is turned off immediately for the rest of the clock cycle. Under this condition, both the high-side and low-side are off until the start of the next cycle.