SNVSBK9C November 2019 – September 2020 LM63635-Q1
The LM63635-Q1 incorporates an undervoltage-lockout feature on the output of the internal LDO (at the VCC pin). When VIN reaches approximately VPOR-R, the device is ready to receive an EN signal and start up. When VIN falls below VPOR-F, the device shuts down, regardless of EN status. Since the LDO is in dropout during these transitions, the above values roughly represent the VCC voltage levels during the transitions. An extended input voltage UVLO can also be accomplished as shown in Section 18.104.22.168.
Thermal shutdown is provided to protect the regulator from excessive junction temperature. When the junction temperature reaches about 163°C, the device shuts down; re-start occurs when the temperature falls to about 150°C.
The LM63635-Q1 features an output voltage discharge FET connected from the SW pin to ground. This FET is activated when the EN input is below VEN-L, or when the output voltage exceeds VRESET-HIGH. This way, the output capacitors are discharged through the power inductor. At output voltages above about 5 V, the discharge current is approximately constant at IPOR or about 1.4 mA. Below this voltage, the FET characteristic looks approximately resistive at a value of 2.5 kΩ.