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Original question:

TLV9301: Peak Detector

TLV9301: Peak Detector

Andres Gomez
Intellectual 450 points
Part Number: TLV9301


Tool/software:

Hi.

I am working on implementing a slow peak detector for our power converter, with the goal of detecting output overloads. We have a circuit that monitors the converter's input current and converts it into a PWM signal. At full load, the PWM signal has a peak voltage of 400mV, a duty cycle of 30%, and a frequency of 100kHz. The peak detector is designed to have a slow response to avoid detecting inrush current at startup, which could trigger a false overload flag and shut down the controller (This inrush current can last 100ms).

The circuit was working fine when I was testing on a test board and connected to the main module. However, when I connected to the main board, the capacitor never discharges. I need to connect the Multimeter and I can see the capacitor discharge. Does it mean that I need to increase the resistor that is connected from OPA Out to GND (1Mohms to 10Mohms)? Or do I need to change the OPAMP from TLV9301 to an instrumental OPAMP lilke OPA189IDBV?



Edit: Sorry, I tried to say when I implemented everything on the main board (layout modification), I saw the issue with the capacitor

  • 0
    TI__Intellectual 2930 points

    Hi Andres,

    To make sure I understand correctly, the capacitor does discharge properly in the layout above as is, but doesn't discharge properly when you implement the layout in the application circuit? 

    If this is the case, could you provide the schematic that includes the main board? 

    Best,

    Alex Curtis

  • 0 in reply to Alex Curtis
    Intellectual 450 points

    I was able to solve the issue by placing the resistor R19 near R20 and C18. In the current layout, that resistor was farway from the RC circuit. I assume the distance affects somehow the way the capacitor discharges

  • 0 in reply to Andres Gomez
    TI__Intellectual 2930 points

    Hi Andres,


    I'm happy to hear that you were able to fix the issue with the discharge capacitor. I'm going to go ahead and mark this thread as closed since it sounds like your issue was resolved, but if you have any other questions feel free to reply to me and the thread will open again.

    Have a great day,

    Alex Curtis