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TPS629210-Q1: The buck output is unstable while the Vin blow 8.6V, with fully loaded I A.

Zhaocai XIANG
Prodigy 70 points
Part Number: TPS629210-Q1
Other Parts Discussed in Thread: TPS629210

Tool/software:

Hello

We are doing the line transient test now. The output of TPS629210 is unstable while the Vin blow 8.6V, with fully loaded I A (Test condition: Vout =3.3V, I-load = 1A  @25℃). According to the datasheet, the input voltage range is 3V to 17V, the output current is up to 1A. Could you help to check what wrong with this test or the Buck?

Channel 1 is the Vin, channel 2 is the output voltage, channel 4 is the external load 750mA(the internal current of the product is about 200mA)

  • 0
    TI__Mastermind 21361 points

    Hi Sir,

    Could you show me the schematic?

    I don't get the  "the internal current of the product is about 200mA"

    Could you also test the SW for this condition?

    It can better help me to check this issue. Thanks!

    Colin

  • 0 in reply to Colin Chen
    Prodigy 70 points

    Hello Colin

    The schematic of this block attached.

    I don't get the  "the internal current of the product is about 200mA"   -- We used this buck in a camera, but normal output current (internal current) for camera is 200mA, and we add 750mA additional load, in order to do the  test the full loaded condition.

    Could you also test the SW for this condition?  -- I think it's just a hardware issue, unrelated to software. What do you think about this?

  • 0 in reply to Zhaocai XIANG
    TI__Mastermind 21361 points

    Hi Zhaocai,

    SW means the switching node, not software.

    Could you test SW and Vout without the external load?

    I am afraid the problem is caused by the load you used.

    Thanks,

    Colin

  • 0 in reply to Colin Chen
    Prodigy 70 points

    Hello Colin

    The following picture shows the buck without additional load in condition Vin=6V, the output is stable.   (CH1:Vin, CH2:Vout, CH3:SW, CH4:I-load)

    The following picture shows the additional load added in condition Vin=6V,  the output is unstable.

    And the following picture shows the additional load added in condition Vin=9V, the output is stable

  • +1 in reply to Zhaocai XIANG
    TI__Mastermind 21361 points

    Hi Zhaocai,

    Looks like your input source don't have enough current supply capability.

    You can see SW has drop in unstable condition. 

    How did you test the VIN? Is that TP310 test point?

    Can you use a external source to test again.

    Thanks,

    Colin