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TLV61070A: Inquiry regarding power drop phenomenon of TLV61070A

Grady Lee
Genius 4165 points
Part Number: TLV61070A

Tool/software:

Hi, TI expert

The customer designed the board by applying TLV61070A as the power for the LED Driver.

However, a phenomenon occurs where the power drops significantly at a 10ms cycle, which is the LED operation cycle.

Increasing the capacity of the input/output Cap. value or adjusting the feedforward cap value does not improve it.

Can you guide me on how to improve the above problem?

[schematic]

[Waveform]

 

Please check.  Thank you.

  • 0
    TI__Expert 8665 points

    Hi Grady,

    Just short Q6 and see if the problem still exists.

    Best Regards,

    Travis

  • 0 in reply to Travis Wang
    Genius 4165 points

    Hi, Travis

    Even if the customer removes Q6 and connects R210 directly (i.e., Q6 is the same as short), the same symptom occurs.

    I will send you a design capture of the relevant part.

    Is there anything else you need to check?

  • 0 in reply to Grady Lee
    TI__Expert 8665 points

    Hi Grady,

    It is not our device behavior that caused this phenomenon. As you can see the Vin drops first before Vout and stays low for a while even when SW is not switching. So our device is not taking any action that can decrease Vin.

    Best Regards,

    Travis

  • 0 in reply to Travis Wang
    Genius 4165 points

    Hi, Travis

    Thank you for response.

    The information was conveyed to the customer, and the information confirmed by the customer is as follows.

    - It is said that the voltage of 3.3V~6V enters TLV76733(TI)_LDO by connecting 1.5V battery in series, and the output 3.3V of TLV76733 enters Vin of TLV61070A.

    - When the FND_PWR_OFF terminal on the circuit diagram is OFF, the waveform is clear, but when the FND_PWR_OFF terminal is ON, the above phenomenon occurs.

    - It seems that the load has an effect because the drop occurs more as the load increases.

    Q1) Is there any relation to the contents of the Device Functional Mode of the TLV61070A?

    Q2) Or is there any part that can be expected to cause the above phenomenon?

    Q3) The customer requested a review of the circuit diagram and PCB layout privately. If you reply to Private E2E or my email (grady.lee@arrow.com), I will send you the schematic and PCB layout. Could you review it?

    (I will create a thread with TLV76733 related to Vin and ask additional questions.)

    Please check. Thank you.

  • 0 in reply to Grady Lee
    TI__Expert 8665 points

    Hi Grady,

    That's strange because FND_PWR_OFF is not controlling anything since Q6 is removed now and R209 is already NC. Can you share waveform with Q6 and Q5 removed?

    According to TI policy, I cannot send e-mail to external account. Do you have a TI FAE that supports the customer?

    Best Regards,

    Travis

  • 0 in reply to Travis Wang
    Genius 4165 points

    Hi, Travis

    I have sent you a Friendship request to send you the schematic and PCB files using private E2E messages.

    If you accept, I will send them to you.

  • 0 in reply to Grady Lee
    TI__Expert 8665 points

    Hi Grady,

    I've checked the schematic, and I still don't understand why FND_PWR_OFF makes a difference when Q6 is not fit. Please share waveform with Q6 and Q5 removed. And add VLDO_IN and VBAT waveform in the screen.

    Best Regards,

    Travis

  • +1 in reply to Travis Wang
    Genius 4165 points

    Hi, Travis

    Since there is no more feedback from customers regarding the question, we will close it for now. T

    hank you for your support.