Datasheet

VOUT

GND

V+

TMP20

3.3V

MONx

AVSS1

UCD90124A

Vout = -11.67mV/°C x T + 1.8583

at -40°C < T < 85°C

REMOTE

TEMP

SENSOR

HOST

READ_TEMPERATURE_2

I2C or SPI

I2C

Faults and

Warnings

Logged Peak

Temperatures

Boolean Logic

UCD90124A

www.ti.com

SLVSAN8 –JANUARY 2012

Figure 12. 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 UCD90124A, it can still

provide the desired temperature to the UCD90124A through PMBus. The host may have temperature

measurements available through I2C or SPI interfaced temperature sensors. The UCD90124A 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.

Figure 13. Host Writing Temperature to UCD90124A

FAULT RESPONSES AND ALERT PROCESSING

The UCD90124A monitors whether the rail stays within a window of normal operation. There are two

Product Folder Link(s) :UCD90124A