SMM665C datasheet(17/36 Pages) SUMMIT

17 / 36 page

SMM665C

Summit Microelectronics, Inc

2125 3.1 7/22/2008

APPLICATIONS INFORMATION (CONTINUED)

FORCE SHUTDOWN

The Force Shutdown operation brings all PUPX

outputs to their inactive state. This operation is used

for an emergency shutdown when there is not enough

time to sequence the supplies off.

The Force

Shutdown operation shuts off all sequenced channels

and waits for the supply voltages to drop below their

respective OFF thresholds.

A Force Shutdown operation can be initiated by any

one of four events. The first two methods for initiating

a Force Shutdown are always enabled. Simply taking

the FS pin to its active state will initiate a Force

Shutdown operation and maintain it until the pin is

brought to its inactive state. An I

2C Force Shutdown

command allows the Force Shutdown operation to be

initiated via software control. This I

2C Force Shutdown

command sets a volatile register bit that triggers a

Force Shutdown.

This bit is cleared after all

sequenced channels have dropped below their OFF

voltage threshold.

During Power-on and Power-off

sequencing, the sequence termination timer can

initiate a Force Shutdown operation.

As described in the previous sections, the sequence

termination timer triggers a Force Shutdown operation

if it times out before the power supply voltages

surpass their voltage thresholds.

This Force

Shutdown will remain active until all sequenced power

supply channels have dropped below their OFF

voltage threshold. While the SMM665C is in ongoing

operations-monitor

mode,

programmed

fault

condition on any power supply channel or on the

12VIN or VDD inputs can trigger a Force Shutdown. A

Force Shutdown resulting from this will remain active

until all sequenced power supply channels have

dropped below their OFF voltage threshold.

For restarting the device, the FS command needs to

be cleared by writing that bit to a zero. This will clear

the command and, if the POWER-ON/OFF pin is not

being forced low externally the SMM665C will begin a

power-on sequence

SMM665C Datasheet(PDF) 17 Page - Summit Microelectronics, Inc.

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