SLVSDN4 June 2017 TPS82150
The internal voltage clamp controls the output voltage slope during startup. This avoids excessive inrush current and ensures a controlled output voltage rise time. When the EN pin is pulled high, the device starts switching after a delay of typically 55μs and the output voltage rises with a slope controlled by an external capacitor connected to the SS/TR pin. Using a very small capacitor or leaving the SS/TR pin floating provides fastest startup time.
The TPS82150 is able to start into a pre-biased output capacitor. During the pre-biased startup, both the power MOSFETs are not allowed to turn on until the internal voltage clamp sets an output voltage above the pre-bias voltage.
When the device is in shutdown, undervoltage lockout or thermal shutdown, the capacitor connected to SS/TR pin is discharged by an internal resistor. Returning from those states causes a new startup sequence.