UCD90120A_15 Datasheet, PDF (18/58 Pages) Texas Instruments – 12-Rail Power Supply Sequencer and Monitor With ACPI Support

UCD90120A
SLVSAN9B – APRIL 2011 – REVISED DECEMBER 2015
www.ti.com
7.4 Device Functional Modes
7.4.1 Power-Supply Sequencing
The UCD90120A 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 I²C
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.
7.4.1.1 Turn-On Sequencing
The following sequence-on options are supported for each rail:
• Monitor only – do not sequence-on
• Fixed delay time (TON_DELAY) after an OPERATION command to turn on
• Fixed delay time after assertion of the PMBUS_CNTRL pin
• Fixed time after one or a group of parent rails achieves regulation (POWER_GOOD_ON)
• Fixed time after a designated GPI has reached a user-specified state
• Any combination of the previous options
The maximum TON_DELAY time is 3276 ms.
7.4.1.2 Turn-Off Sequencing
The following sequence-off options are supported for each rail:
• Monitor only – do not sequence-off
• Fixed delay time (TOFF_DELAY) after an OPERATION command to turn off
• Fixed delay time after deassertion of the PMBUS_CNTRL pin
• Fixed time after one or a group of parent rails drop below regulation (POWER_GOOD_OFF)
• Fixed delay time in response to an undervoltage, overvoltage, or max turn-on fault on the rail
• Fixed delay time in response to a fault on a different rail when set as a fault shutdown slave to the faulted rail
• Fixed delay time in response to a GPI reaching a user-specified state
• Any combination of the previous options
The maximum TOFF_DELAY time is 3276 ms.
(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.
18
Submit Documentation Feedback
Copyright © 2011–2015, Texas Instruments Incorporated
Product Folder Links: UCD90120A