• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 30 subscribers
  • Views 316 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMP390: Sensor outputs not triggering at set temperature

Matthew Anauo
Prodigy 140 points
Part Number: TMP390

Tool/software:

I have constructed the below circuit to provide temperature lockout/protection to our device. The goal is to disable a buck converter when temperature is outside the range [-40C - 120C]. The CH. A/B outputs are tied together with diode logic and connected to the enable pin of the buck converter. In testing our devices, so far we have tested 15 units. 13 have performed as expected, but one failed to trigger the CH. A output (was tested up to 135 and never asserted) while another failed to trigger the CH. B output (was tested down to -55 and never asserted).

The prototype run we are testing consists of QTY-200 units. It is looking like we are going to have to evaluate every unit to determine the extent of this issue. Is this a normal yield for this product? The exact PN is TMP390A3DRLR, is different performance expected of -Q1 parts? I'm trying to determine the root cause of the problem and how to resolve it.

  • 0
    TI__Expert 4790 points

    Hello Matthew,

    Sorry to hear you're having trouble with your setup. Please see my comments regarding the circuit below:

    1. Could we see the circuit to the right of the diodes? I'm particularly curious about the specs of the buck that is being used and how it's set up.

    2. What was the purpose of adding diodes to the circuit? I suspect there's a chance the output of the diodes may be too low and not equal to the VOL of the buck.

    3. The TMP390 can have its outputs tied, so you would also be able to eliminate one of your pull-up resistors.

    Regards,

    Harry

  • 0 in reply to HarryG
    Prodigy 140 points

    1. This is the buck converter.

    2. Intent of the diodes was to disconnect the UVLO divider from the impedance of the pull-ups and to give the logic of asserting the buck converter enable pin low if either temperature channel was triggered. To your point - that was my suspicion as well, but on the two units we've found that failed, probing the output of the TMP390 directly at the component pin (i.e. before the diode) shows that the output is not asserting.

    3. Noted - thank you.

    Update - After seeing two failures in a small batch, we began going through the rest of our 200-pc prototype build and testing this issue. So far through ~125 of those boards not a single other one has shown this issue. If we go through the rest of the build and none have the issue, the most likely explanation seems like damage from handling/testing prior to the thermal shutoff test.

  • +1 in reply to Matthew Anauo
    TI__Expert 4790 points

    Understood. Please keep me updated in the meantime if there are any more problem devices and we can troubleshoot from there.


    Regards,

    Harry