UCD90910 Datasheet, PDF (19/51 Pages) Texas Instruments – 10-Rail Sequencer and System Health Monitor With 10-Fan Control

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UCD90910
SLVSA81 – JULY 2010
UCD90910
TMP20
MONx
VOUT
AVSS1
GND
3.3V
V+
Vout = -11.67mV/°C x T + 1.8583
at -40°C < T < 85°C
Figure 11. Remote Temperature Monitoring Circuit Example Using the TMP20
TEMPERATURE BY HOST INPUT
If the host system has the option of not using the temperature-sensing capability of the UCD90910, it can still
provide the desired temperature to the UCD90910 through PMBus. The host may have temperature
measurements available through I²C or SPI interfaced temperature sensors. The UCD90910 would use the
temperature given by the host in place of an external temperature measurement for a given rail. The temperature
provided by the host would still be used for detecting overtemperature warnings or faults, logging peak
temperatures, input to Boolean logic-builder functions, and feedback for the fan-control algorithms. To write a
temperature associated with a rail, the PMBus command used is the READ_TEMPERATURE_2 command. If the
host writes that command, the value written will be used as the temperature until another value is written. This is
true whether a monitor pin was assigned to the temperature or not. When there is a monitor pin associated with
the temperature, once READ_TEMPERATURE_2 is written, the monitor pin is not used again until the part is
reset. When there is not a monitor pin associated with the temperature, the internal temperature sensor is used
for the temperature until the READ_TEMPERATURE_2 command is written.
UCD90910
REMOTE
I2C or SPI
I2C
TEMP
HOST
SENSOR
READ_TEMPERATURE_2
Fan Control
Faults and
Warnings
Logged Peak
Temperatures
Boolean Logic
Figure 12. Temperature Provided by Host
FAULT RESPONSES AND ALERT PROCESSING
Device monitors that the rail stays within a window of normal operation. There are two programmable warning
levels (under and over) and two programmable fault levels (under and over). When any monitored voltage,
current, or temperature goes outside of the warning or fault window, the PMBALERT# pin is asserted
immediately, and the appropriate bits are set in the PMBus status registers (see Figure 6). Detailed descriptions
of the status registers are provided in the UCD90xxx Sequencer and System Health Controller PMBus Command
Reference and the PMBus Specification.
Copyright © 2010, Texas Instruments Incorporated
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