DocID027688 Rev 3

17/28

PM8908

Device description

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threshold and the device acts as follows:



De-asserts the PGOOD signal



The HS MOSFET is suddenly forced OFF



The LS MOSFET is turned on (to discharge the output and protect the load). When

discharge resistor is off.

In the overvoltage protection state the negative overcurrent limit (OCLN) is masked.

This protection is latched, cycled EN or VCC to recover.

5.4.2

Undervoltage protection

If VOUT falls below the UVP threshold for at least 256

s the IC stops switching and starts

a soft-off sequence.

The device acts as follows:



De-asserts the PGOOD signal



The HS MOSFET and LS MOSFET are forced OFF



The discharge resistor is on.

This protection is latched, cycled EN or VCC to recover.

The UVP protection is enabled after the soft-start end.

5.4.3

Power Good (PGOOD)

The PGOOD is an open drain output. During the startup, the PGOOD goes high after 1 ms

from the threshold detected.

The PGOOD is forced low, to communicate that the output voltage is no longer in regulation,

if one of the following conditions is verified:





The device is disabled, EN is forced low



VCC voltage is below the UVLO threshold



Any protection is triggered (OVP, UVP, OTP).

5.4.4

Overcurrent protection

Overcurrent protection is active as soon as the device is enabled and VCC voltage is above

the UVLO level.

The overcurrent function protects the converter from a shorted output or overload by

sensing the output current information across the low-side integrated MOSFET.



Positive OCL

If the monitored current information is bigger than the overcurrent thresholds, an overcurrent

limit.