ZHCSL05C October 2019 – October 2023 TPS65313-Q1
PRODUCTION DATA
The currents through the high-side (HS) power MOSFET and the low-side (LS) power MOSFET are continuously monitored to protect the internal MOSFETs from damage. Cycle-by-cycle currents through the HS MOSFET and LS MOSFET are compared against the IHS_ LIMIT_BOOST and ILS_ LIMIT_BOOST current limits, respectively.
As load current increases to greater than the maximum IBOOST_LOAD current defined in Section 9.9, the HS MOSFET current exceeds the IHS_LIMIT_BOOST current limit. Consequently, an overload event is detected and the BOOST_HS_OVC status bit is set in the SAFETY_BOOST_STAT1 register. However, the regulator does not shut down. If the load current continues to increase, the LS MOSFET current exceeds the short-circuit current limit (ILS_LIMIT_BOOST). The LS MOSFET is turned off immediately and the HS MOSFET is turned on until the inductor current decreases to less than the overload threshold (IHS_ LIMIT_BOOST). The BOOST converter is then disabled and the BOOST_SCG status bit is set in the SAFETY_BOOST_STAT1 register. The BOOST_EN control bit is cleared and the device goes into the SAFE state, where the device error counter increments and the ENDRV/nIRQ pin is driven low. If the BOOT_UV_RST_EN bit is set to 1b (BOOST UV event configured as RESET state condition), as the VBOOST voltage rail is discharged to less than its UV-threshold level, the device goes into the RESET state.
The HS MOSFET is also protected by detection circuitry for a cycle-by-cycle sink-current limit. This detection circuitry protects the HS MOSFET from excessive reverse current caused by switching the PH3 pin to the VSUP2 supply pin. If the HS sinking current exceeds the ICL_HS_SINK_BOOST sink-current limit, an event is detected and the BOOST_HS_SINK_OVC SPI status bit is set in the SAFETY_BOOST_STAT1 register. If the event occurs for more than 20 µs (typical), the BOOST converter is turned off. The inductor current continues to flow to the supply (VBUCK1 voltage rail) through the body diode of the LS MOSFET. The device response after detection of a HS sink-current limit is identical to that of a short-circuit event.
The HS sink current-limit event can also be detected when the regulator is enabled while its output has not been discharged to less than the voltage level defined by the VBOOST_RESTART_LEVEL level. Therefore, the HS sink current-limit event is masked when the BOOST converter is enabled until it the output voltage ramps to greater than its UV-threshold level.
After receiving an interrupt, the MCU can try to enable the BOOST converter again by sending command to set the BOOST_EN control bit. If a current-limit condition is still present, the BOOST converter is switched off again and the device error counter increments.