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LM73100EVM: DV/DT leakage

GARETH OU
Guru 11375 points
Part Number: LM73100EVM

Hi

Use EVM of LM73100 to make Oring circuit, when one of them has no input,

The LM73100 without electricity has leakage at the DV/DT pin, which is about 16.xV When the input voltage is 19V

1. Will it cause damage to the IC?

2. Why is there will be leakage design, this is normal?

  • 0
    TI__Guru* 79181 points

    Hi Gareth,

    1. Have you done any changes to EVM?

    2. How have you made ORing circuit? Have you used the two channels available on same EVM?

    3.You are applying 19V at one input and making other input zero?

    4. The LM73100 without input has leakage? What do you mean by 16.xV? By leakage you mean current flowing IN/OUT of DVDT pin? What is CDVDT cap value?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Guru 11375 points

    Hi Kunal

    1. Have you done any changes to EVM?

    19V input, so when testing, adjust R11/R17 to 118K, remove D2/D8, and R24 is the upper part

    2. How have you made ORing circuit? Have you used the two channels available on same EVM?

    Customer use two channel of the same EVM for testing

    3.You are applying 19V at one input and making other input zero?

    Yes

    4. The LM73100 without input has leakage? What do you mean by 16.xV? By leakage you mean current flowing IN/OUT of DVDT pin? What is CDVDT cap value?

    When a 19V DC voltage is input to J5, U1 works normally, but U2 does not work; When measuring the surrounding voltage of U2, it is found that the voltage of TP14 (dvdt2) has a voltage of 16.78V

  • 0 in reply to GARETH OU
    TI__Guru* 79181 points

    Hi Gareth,

    Any other observation on U2? Is U2 blocking reverse current from output to input? Is channel 2 working fine individually with no ORing?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Guru 11375 points

    Hi Kunal

    U2 did stop it during Oring. But there is voltage on the dv/dt2 pin
    When it’s not Oring, either way alone can work normally

  • 0 in reply to GARETH OU
    TI__Guru* 79181 points

    Hi Gareth,

    Thanks for your response. I will get back to you on this. Sorry for more questions.

    Are you not connecting U2 input to a voltage source or shorting the pin to GND? 

    Also do you know what is the voltage at dvdt pin of U1 when U2 is given 19v and U1 input is zero? 

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Guru 11375 points

    Hi Kunal

    1.Only one set has power, u2 usually has no power , but u2 is not connected to ground

    2.U1 does not work, when only U2 works, TP2 also has a voltage of about 17V

    If you need to provide you with measurement data , please let me know 

    Thanks you

  • 0 in reply to GARETH OU
    TI__Guru* 79181 points

    Hi Gareth,

    Thanks for information. It would be nice if you can provide measurement data. Meanwhile I am also checking with team on this issue.

    Regards

    Kunal Goel

  • +1 in reply to Kunal Goel
    TI__Guru* 79181 points

    Hi Gareth,

    The voltage on DVDT pin is normal and will not cause any issue in customer application and our device. As you can see in block diagram in datasheet there is FET between VOUT and CDVDT. This FET discharges DVDT to OUT after PG. As U2 has no power so this FET is off and the body diode of this FET is causing the dVdt to rise. 

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Guru 11375 points

    Hi Kunal

    Thank you very much
    For oring also need to pay attention?

  • 0 in reply to GARETH OU
    TI__Guru* 79181 points

    Hi Gareth,

    This voltage at DVDT is expected. It will not cause problem in ORing.

    Regards

    Kunal Goel