Any time the output voltage falls more than a few percent, output voltage ramps up slowly. This condition, called graceful recovery from dropout in this document, differs from soft start in two important ways:
- The reference voltage is set to approximately 1% above what is needed to achieve the existing output voltage.
- If the device is set to FPWM, it will continue to operate in that mode during
its recovery from dropout. If output voltage were
to suddenly be pulled up by an external supply,
the LMR436x0-Q1 can pull down on the output. Note
that all protections that are present during
normal operation are in place, preventing any
catastrophic failure if output is shorted to a
high voltage or ground.
Figure 8-11 Recovery from Dropout Figure 8-12 Typical Output Recovery from Dropout from 8 V to 4 V
Whether output voltage falls due to high load or
low input voltage, once the condition that causes output to fall below its set point
is removed, the output climbs at the same speed as during start-up. Figure 8-12 shows an example
of this behavior.