SLVSA30D April 2011 – March 2019 UCD9090
PRODUCTION DATA.
Another method to cascade multiple devices is to connect the power-good output of the first device to a MON pin of the second device, connect the power-good output of the second device to a MON pin of the third device, and so on. As an option, connect the power-good output of the last device to a MON pin of the first device. The rails controlled by a device have dependency on the power-good output of the previous device. This method allows the rails controlled by multiple devices to be sequenced.
The de-assertion of a power-good output can trigger an undervoltage fault of the next device in the chain. The undervoltage fault response can be configured to shut down other rails controlled by the same device. This process ensures that when one rail has fault shutdown, other rails controlled by other devices can be shut down in the same way.
The PMBus specification implies that the power-good signal is active when ALL the rails in a controller are regulating at their programmed voltage. The UCD9090 allows GPIOs to be configured to respond to a desired subset of power-good signals.