ZHCS360F July 2012 – November 2020 TPS54020
PRODUCTION DATA
While the low-side MOSFET is turned on, its conduction current is monitored by the internal circuitry. During normal operation, the low-side MOSFET sources current to the load. At the end of every clock cycle, the low-side MOSFET sourcing current is compared to the internally-set low-side sourcing current limit. If the low-side sourcing current is exceeded, the high-side MOSFET is not turned on and the low-side MOSFET stays on for the next cycle. The high-side MOSFET is turned on again when the low-side MOSFET current is less than the low-side MOSFET sourcing current limit at the start of a cycle.
To boost efficiency in light load conditions, the control circuitry does not allow the low-side MOSFET to sink current from the load. When negative low-side MOSFET current is detected, the low-side MOSFET is turned OFF immediately for the rest of that clock cycle. In this scenario, both MOSFETs are off until the start of the next cycle.
Additionally, if an output overload condition (as measured by the COMP pin voltage) has lasted for more than the hiccup wait time which is programmed for 128 switching cycles, the device shuts down and restarts only after the hiccup time of 16384 cycles has elapsed. The hiccup mode helps to reduce the device power dissipation under severe overcurrent conditions.