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Temperature sensor-TMP411 - Remote temperature meaurement

Srivatsa Raghunath
Prodigy 180 points
Other Parts Discussed in Thread: TMP411, TMP431

We're facing an issue with TMP411 with remote temperature measurement. We've used this to measure the junction temperature of Intel IXP processor. Connection details are shown in attached snaps shot

Observation - TMP  ALERT/THERM2 pin is never com up if IXP power is switched OFF

We have to cool down the processor junction temperature well below value the thermal limit set in TMP411 , Alert pin never comes up if we don't power down the IXP.  ALERT/THERM2  pin will be return back to high state after the junction temperature reaches below set value. ALERT/THERM2  signal is used to control the ON board power supply , once it low all on board power will be switched OFF , only TMP411 power will alive under this conditions

Pls clarify

 
TMP411_connection details.zip
  • 0
    TI__Expert 7185 points

    Srvatsa,

    To be able to better assist with this issue it will be very helpful for you to post a read of the status and remote temperature registers as this will indicate which fault it tripping the ALERT pin.  Also, I would highly recommend lowering your series resistance to no larger than 100 ohms and reducing your differential capacitor to <= 50pF.  Processors such as the INTEL IXP can emit high frequency noise and since the device already has an internal low pass filter with a cutoff of 65kHz it is more effective to move the external low pass filter out to a higher frequency (i.e. > 10MHz) to avoid a sampling error on the internal ADC.  This may not be what is causing your problem; however, keep in mind that a large sampling error could cause an erroneous temperature read and if the temperature is outside the Thigh or Tlow limit this will most definitely trip the ALERT pin.

    Matt

  • 0
    TI__Mastermind 43815 points

    I'm curious. What is the supply voltage of the processor? Is it 45nm?

    If it is 45nm you should consider switching to TMP431, but definitely follow-up with Matt and his questions first.