Datasheet

UCD90124A

SLVSAN8 –JANUARY 2012

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Figure 8. Fusion GUI Flash-Error Log (Logged Faults)

POWER-SUPPLY SEQUENCING

The UCD90124A can control the turn-on and turn-off sequencing of up to 12 voltage rails by using a GPIO to set

a power-supply enable pin high or low. In PMBus-based designs, the system PMBus master can initiate a

sequence-on event by asserting the PMBUS_CNTRL pin or by sending the OPERATION command over the I

serial bus. In pin-based designs, the PMBUS_CNTRL pin can also be used to sequence-on and sequence-off.

The auto-enable setting ignores the OPERATION command and the PMBUS_CNTRL pin. Sequence-on is

started at power up after any dependencies and time delays are met for each rail. A rail is considered to be on or

within regulation when the measured voltage for that rail crosses the power-good on (POWER_GOOD_ON

(1)

)

limit. The rail is still in regulation until the voltage drops below power-good off (POWER_GOOD_OFF). In the

case that there isn't voltage monitoring set for a given rail, that rail is considered ON if it is commanded on (either

by OPERATION command, PMBUS CNTRL pin, or auto-enable) and (TON_DELAY +

TON_MAX_FAULT_LIMIT) time passes. Also, a rail is considered OFF if that rail is commanded OFF and

(TOFF_DELAY + TOFF_MAX_WARN_LIMIT) time passes

(1) In this document, configuration parameters such as Power Good On are referred to using Fusion GUI names. The UCD90xxx

Sequencer and System Health Controller PMBus Command Reference name is shown in parentheses (POWER_GOOD_ON) the first

time the parameter appears.

Product Folder Link(s) :UCD90124A