When designing with
the TPSM365Rx, slow
rise in output voltage due to recovery from dropout and soft
start must be considered as a two separate operating
conditions, as shown in Figure 9-11 and Figure 9-12. Soft start is triggered by any of the following
conditions:
- Power is applied to the VIN pin of the
device, releasing undervoltage lockout.
- EN is used to turn on the device.
- Recovery from shutdown due to
overtemperature protection.
After soft
start is triggered, the power module takes the following
actions:
- The reference used by the power module
to regulate the output voltage is slowly ramped
up. The net result is that output voltage, if
previously 0 V, takes tSS to reach 90%
of the desired value.
- Operating mode is set to auto mode of
operation, activating the diode emulation mode for
the low-side MOSFET. This allows start-up without
pulling the output low. This is true even when
there is a voltage already present at the output
during a pre-bias start-up.