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.

LM74610-Q1: LM74610-q1 charge pump glitch

Part Number: LM74610-Q1
Other Parts Discussed in Thread: DRV8912-Q1EVM, LM74700-Q1

Hello,

I am using LM74610-Q1 is DRV8912-Q1EVM. We found the charge pump capacitor voltage glitch about every 1.1s.

Do you see any issue with the following circuit?

  • Hi Wang Li,

    The LM74610-Q1 is a zero-Iq device.

    LM74610-Q1's charge pump is charged through the body diode drop when the FET is turned OFF.

    Once the charge pump is fully charged, FET is turned ON again. Next the charge pump will loose charge and slowly decay. Once it reaches

    a threshold, MOSFET is turned off. The Voltage drop of body diode is used to charge the charge pump. This process repeats as shown in Figure 9 of datasheet.

    Regards,

    Kari.

  • Kari,

    Thank you for your reply. The FET turn-off behave causes some trouble to my EVM. Do you know any other part don't have this glitch? Or any workaround solution to keep FET on?

  • Kari,

    "LM74610-Q1's charge pump is charged through the body diode drop when the FET is turned OFF."

    Also, if put a paralleling schottky diode to reduce the voltage drop when the FET is turned off. Any side effect? Is the refresh pulse more frequently since the voltage across body diode is reduced?

    If there is a pin to pin compatible part, it would be good.
  • Hi Wang Li,

    We have LM74700-Q1 which does not have a refresh pulse and we strongly recommend this device here.
    This is not pin-pin compatible with LM74610-Q1.

    On the follow up question, adding a schottky diode would reduce the voltage drop, but the refresh cycle time will be reduced.

    There is not pin-pin compatible solution, but our suggestion to get rid of pulse is to add an inductor between the LM74610-Q1 output (Cathode) and the output capacitors.

    This would form an LC filter which would filter out the pulsed cathode output.

    Regards,
    Kari.
  • Kari,

    Got it. Thanks,