LM2903: LM2903DR issue

Part Number: LM2903
Other Parts Discussed in Thread: LM339

Hi team,

My customer test LM2903DR in their new project. But the EOS damage was observed in it.

Could you please help review the schematics and give some modification suggestions?

Thank you!

B11 is 12-0.7=11.3V;

B10 input is a pulse signal, amplitude high 12V, low 0V;

  • Hello Ivy,

    I do not see anything in the supplied circuit that would cause a catastrophic failure. The resistors are large enough to limit current to below abs-max.

    Can we get the complete schematic, including the other channel. You can send it internally if you do not want to post.

    Because this is a junction-isolated device, a stress on one channel can affect the others - so a stress on one channel can blow another channel depending on what junctions were activated. I would also scope-out the other channel and not just the failed channel.

  • Hi Paul,

    Thanks for your reply.

    The B10 input is a pulse signal with a high amplitude of 12V and a low amplitude of 0V.

    In addition, I will check with my customer to get the full schematic, Thank you!

    Regards,

    Ivy

  • Hi Paul,

    These are the schematics of VPP1.

    The customer said these are all the schematics related to LM2903DR.

    Could you please help check and give some comments?

    Thank you in advance!

    Regards,

    Ivy

  • Hi Ivy,

    what is the voltage at pin "Q" of TLE4250? I ask because if the TLE4250 is damaged, the full battery voltage could reach the supply voltage pin of LM2903 and destroy it. Is the "Q" output always emitting +12V, even during power-ups and power-downs?

    Also, as this seems to be an automotive project (series circuits of ceramic caps to enhance the reliability Relaxed), are you sure the circuit does survive all the nasty under- and overvoltage situations very likely occuring in such applications? Is there a chance that an unhealthy voltage can reach the LM2903? Maybe another TVS directly across the LM2903's supply pins is a good idea?

    The same with B10. Are you sure there's never an unhealthy voltage reaching the inputs of LM2903?

    Kai

  • Hello Ivy,

    I still do not see any "dangers". The inputs have large (>10k) resistors on all the inputs to limit current to 1.2mA worst case.

    So they are saying the *other* channel is identical?? Redundancy?

    Is the failure repeatable? Or random? What is the main BAT voltage?

    They are exceeding the input voltage range on the non-inverting input (pin 3). The limit is Vcc-2V, or 10V on a 12V supply. Though this device has a "feature" where it will still respond correctly as long as one input is still within range, it should not damage it. 11V/33k = 333uA, well below the Abs Max.

    Please see the LM339 family application note, particularly sections 2.2 and 2.5:

     https://www.ti.com/lit/an/snoaa35a/snoaa35a.pdf

    The only thing that I can think of causing that amount of damage is a supply transient or latch-up. Either a large negative supply transient or going above +40V.

    As Kai eluded to, the TLE4250G is a Voltage Tracker, not a regulator, and the reference is a simple zener. So I cannot assume that the output is a steady 12V as with a self-contained regulator with OV and UV limits.

     I *really* recommend using a 4-channel scope and watch the V+, IN+, IN- and the OUTPUT pins. They should run through the entire power-up, normal operation, and power-down sequence (including a few seconds after power-down to watch for final "whumps"). Do this on both channels. You would be surprised what can happen during power-up and down.

  • Hi Paul and Kai,

    Thanks for your help!

    I will push my customer to do these test as you said, the reply may be delay.

    Appreciate your help!

    Regards,

    Ivy

  • Ivy

    we will await their response.

    Chuck

  • Ivy

    Hope this response finds you well.  Did you ever receive any additional input?  If needed, I can extend the time we leave this open, but it may be best to take this offline to avoid the thread being lost if we do not expect any new information soon.

    Thanks, Chuck

  • Hi Chuck,

    Your suggestions were very helpful. So far, I haven't receive any new input. I'll contact you offline if the customer feedback me in the future.

    Thanks you!

    Regards,

    Ivy