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.

LM5161: Vcc will increase when Vin plug the 48V battery input

Part Number: LM5161

Dear Expert

Below is waveform measurement data on actual circuit application of LM5161PWPT. 

-the abnormal 20V peak voltage was occurred on pin-10 (VCC pin) when hot plugging process (power on input DC voltage to input pin-3 of LM5161PWPT by manual plugging of external 56V connector).

- the abnormal 20V peak voltage issue is not occurred when cool plugging process (manually insert the connector of external 56V first, then power on input 56V DC voltage to LM5161PWPT).

  • Hello Gabriel,

    Thank you for posting.  Due to the e2e Maintenance, I just see your post now.  I will need to check with our team especially the engineer who supports it previously.  I will try to get back to you by COB next Tue the USA time.

    Meanwhile, would you please share the waveforms, too?

    Thanks,

    Youhao

  • Dear Youhao

    Test waveforms:

    CH1(Yellow): the voltage across C52(or the voltage on pin 8&10)    CH2(Blue):  12VDC output(TP3)           CH3(Red): 56VDC from the 56V mercury

    The max peak voltage on pin 8 & 10 is about 20VDC.

    Zoom:

  • Hi Gabriel,

    Thank you for the waveform.    I am afraid the VCC voltage spike was not realistic but affected by the regular probe's long ground leads. Would you please use the probe with short ground lead to monitor VCC?

    Thanks,

    Youhao

  • Dear Youhao

    he over voltage result has been captured on pin-10 for more times.

  • Hi Gabriel,

    I will ask our engineer to see if we can duplicate this on the EVM.   I will update you in the next couple of days.

    Meanwhile, could you ask the customer to place a 100nF capacitor across R68 and see it the issue is resolved?

    Thanks,

    Youhao

  • Hi Garbriel,

    Just a brief update:  our engineer is ordering an EVM--we do not have in our lab, and will run the test.  It may take several days for the EVM to show up.  Sorry for the delay. I will update as soon as we get the results. 

    Best Regards,

    Youhao