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INA214: Output is high as there is no load current flow at -25 ℃

Harry Ma
Intellectual 2805 points

Part Number: INA214

Tool/software:

Hi Team

Customer is using INA214 as output current sense in a industry power supply project at low side. they found there is one pcs of total 3pcs which output will be 2V which will trigger OCP to cause the power start-up failure at -25 ℃ ambient temperature. but there is no current on load.

and the output will be zero when increase the ambient temperature to 25℃ and everything works normal. It is tricky for customer.

Can you show your insight what is the possible root-cause of this issue or what we should do next step yo identify the root-cause

  • 0
    TI__Mastermind 32395 points

    Hey Harry,

    I’m not sure if this is related to the problem, but can you confirm why the INA214’s IN+ pin is connected to the “48VRTN” net. I would suspect that load current would flow into 48VRTN which means INA214 is sensing a negative shunt voltage drop.

    Can the INA214 sense current as expected at 25C?

    Aside from that, can I get some information on how 48VRTN is connected to the INA214 GND pin (“3.3V_S_GND”)? We should confirm that these nets are connect with a very low impedance connection and there is no ground loop that creates a differential voltage at -25C.

    With the problematic system, can customer please probe INA214 GND pin directly and the 48VRTN net (essentially IN+) pin at -25C? A differential probe would be best, but two single ended probes should be fine too.

    After this it would be good to perform an A-B-A swap of INA214s from abnormal and working systems. Before resoldering the devices (good and bad) I would recommend measuring all pin-to-GND pin resistances with simple Ohm meter to check for significant difference between the INA214 units.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    TI__Intellectual 2805 points

    Hi Peter

    Customer is checking there question and I will give you a feedback later.

    and there is another project is using INA214BIDCKR as well.  the layout and schematic shown as following. it is placed at low side, customer found that when they short the output by a circuit breaker, the input reaches to 600mV almost, but  the INA214's output is still be low which cause OCP can't trigger.

    Is there any thing wrong? Pls help to give your insight what is the next step I identify the root cause of this quetsion?

  • 0 in reply to Harry Ma
    TI__Mastermind 32395 points

    Hey Harry,

    The new circuit you have sent seems to also have potential issue with the polarity of the shunt voltage. You show current flowing from IS3 to 55V_GND, so the positive shunt voltage drop is measured IS3 - 55V_GND>0. However, the INA214's inverting pin is connected to IS3, which means INA214 is sensing a negative voltage drop. Given that REF=GND, this means Vout will not respond and stay saturated at 0V.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    TI__Intellectual 2805 points

    Peter

    the same circuit, TP182A can works, it's p2p with INA214. and we tested the voltage drop of INA+ minus INA- with rated load and short of output.

    you can see the voltage drop's polarity is same. 

  • +1 in reply to Harry Ma
    TI__Mastermind 32395 points
    • Hey Harry,

    So if device is really measuring a positive 600mV (55V_GND > IS3) , then this actually means there is a possible violation input pin Absolute Maximum and operational Voltage (Vin- < -100mV). I say this because the I + pins is device ground.

    So this may be causing damage or at least be rendering the device inoperable/unresponsive.

    Wouldn’t this also forward bias C24? This could certainly creat some input offset that saturate device.

    We need some single ended probing of all device input pins with respect to GND pin.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    TI__Mastermind 32395 points

    Hey Harry,

    Since we have not heard back from you, I will mark this thread as resolved. However, it you have any other updates or questions, you can simply reply back here or start a new thread.

    Best,

    Peter

  • 0 in reply to Peter Iliya
    TI__Intellectual 2805 points

    Thanks Peter. it is resolved