Datasheet

UCD90124A
www.ti.com SLVSAN8 –JANUARY 2012
THEORY OF OPERATION
Modern electronic systems often use numerous microcontrollers, DSPs, FPGAs, and ASICs. Each device can
have multiple supply voltages to power the core processor, analog-to-digital converter or I/O. These devices are
typically sensitive to the order and timing of how the voltages are sequenced on and off. The UCD90124A can
sequence supply voltages to prevent malfunctions, intermittent operation, or device damage caused by improper
power up or power down. Appropriate handling of under- and overvoltage faults can extend system life and
improve long term reliability. The UCD90124A stores power supply faults to on-chip nonvolatile flash memory for
aid in system failure analysis.
Tach monitor inputs, PWM outputs and temperature measurements can be combined with a choice between two
built-in fan-control algorithms to provide a stand-alone fan controller for independent operation of up to four fans.
System reliability can be improved through four-corner testing during system verification. During four-corner
testing, the system is operated at the minimum and maximum expected ambient temperature and with each
power supply set to the minimum and maximum output voltage, commonly referred to as margining. The
UCD90124A can be used to implement accurate closed-loop margining of up to 10 power supplies.
The UCD90124A 12-rail sequencer can be used in a PMBus- or pin-based control environment. The TI Fusion
GUI provides a powerful but simple interface for configuring sequencing solutions for systems with between one
and 12 power supplies using 12 analog voltage-monitor inputs, four GPIs and 22 highly configurable GPIOs. A
rail includes voltage, a power-supply enable and a margining output. At least one must be included in a rail
definition. Once the user has defined how the power-supply rails should operate in a particular system, analog
input pins and GPIOs can be selected to monitor and enable each supply (Figure 4).
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