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TPS7A02: quiscent current high

Julien Campos
Prodigy 40 points
Part Number: TPS7A02

Hello,

I have tried to check the quiescent current of the TPS7A02 in no-load condition. According to the datasheet, that is around 25 nA.
I have used the TPS7A0220PDBVR version, 2V output, SOT 23-5 package.
I have soldered the chip on a prototype SOT 23-5 breadboard compatible.
I have soldered a 0402 100nF X5R between the 2 leads VIN and GND.
I haven't soldered a decoupling capacitor at the output, having no TH capacitor with me.
I have connected an SMU Keithley 2450 on VIN, voltage mode, 3V, 1Amp compliance limit.
I have connected a multimeter Keithley DMM6500 on Vout, with 10 MOhm impedance.
Vin is connected on the breadboard to the EN pin.
No load is connected (apart from the 10 MOhm input impedance).
When starting the experience:
Vout = 2.05V --> OK
Iq around 2 mA
If I redo the experience without the multimeter connected, same results.
I don't understand why I obtain a value so high compared to the datasheet saying it should be 25 nA.
Thanks for the help.
Regards,


Julien

  • +1
    TI__Mastermind 29140 points

    Hi Julien,

    There are a couple of things to check or review.

    1. I'm worried that the device may be unstable.  It requires an output capacitor for stability.

    2. Please make sure that the board has been completely cleaned from flux residue.  This residue can leave a conductive film which can result in leakage current.  We see this from time to time each year in customer hardware, so it's something that you should check.  A flux cleaner or DI bath is recommended.

    Thanks,

    Stephen

  • 0 in reply to Stephen Ziel
    TI__Genius 12040 points

    Hi Julien,

                   I agree with Stephen, please add an output cap (1uF at least) to stabilize the part. Very likely this is your issue. Please also verify the cleanliness of the board with a flux remover and/or DI bath. Thanks!

    Regards,

    Srikanth

  • 0 in reply to Srikanth Lolla Venkata
    Prodigy 40 points

    Hi Srikanth,
    Thanks. I have applied that correction, like Stephen also suggest. It solved the issue (see comment above to Stephen).
    Thanks for your support!
    Regards
    Julien 

  • 0 in reply to Stephen Ziel
    Prodigy 40 points

    Hello Stephen,
    I found a way to solder a 1 uF 0402 cer cap at Vout and wire it to the GND. That was enough to solve immediately the problem and bring back stability. 
    I have 2V on Vout, and I measured Iq around 30 nA after disconnecting the multimeter on Vout (10 MOhm). This value is in line with the datasheet.
    Thanks for your help!

    Julien