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TPS782: Quiescent Current of TPS782

Dylan Vo
Prodigy 20 points
Part Number: TPS782

Hi guys,

We are having some trouble with TPS782, particularly TPS78228DDCR. My product is for Water meter device which needs the very low current when the device sleep.

We are in producing and we find the Quiescent Current of TPS78228DDCR is much high than the SPEC of TI (~25uA instead 1uA).

We have tested by measure the current on board only have the TPS78228DDCR IC, no power, no other components. I measure the GND pin current when the output current is 0mA, like the SPEC of TI.

I afraid our method is fail in somewhere. I really wanna know the exactly method to measure Quiescent Current.

Moreover, The SPEC of TI just no mentions about the range of Iq Quiescent Current, that makes me so difficult to confirm the test result.

Hope guys can help me with this problem.

The attached image of TI's SPEC:

76e7370e02c7c7999ed6.jpg

Many thanks.

  • TI__Genius 12565 points

    Hi Dylan, 

    Can you show me how you are measuring Iq? Also, can you share your schematics? Is there a resistor on the EN pin? 

    Best, 

    Edgar Acosta

  • Prodigy 20 points
    Hi Edgar,
    We just measure only IC on board, no resistor. You can see in video I send.
    Hope for your reply soon.
    Thanks.
  • in reply to Dylan Vo
    TI__Genius 12565 points

    Hi Dylan, 

    Thank you for sharing this. 

    One of the ways we measure Iq is by measuring the current from Vin to GND, is this how you are measuring current, or are you measuring at Vout?

    I see that the PCB is labeled IC Old and IC new, and for the one Labeled OLD its reading a 0.4uA, what is the difference between these two boards and/or IC? 

    Best, 

    Edgar Acosta

  • in reply to Edgar Acosta1
    Prodigy 20 points

    Hi Edgar,

    Yeah, We measured Iq at Vin.

    The PCBs are not different, only ICs are different. We bought IC old from 4 months ago while IC new just 1 months ago. So I wonder if the quality of ICs are no change, maybe the method we measure is wrong. I would like to confirm what is the origin of this problem.

    Then, if the problem come from the unqualified IC, Could you help me to explain what makes the quality of IC decrease?

    Thanks so much,

  • in reply to Dylan Vo
    TI__Genius 12565 points

    Hi Dylan, 

    The methodology is correct, using the DMM in series to measure the current flowing from Vin to GND should be enough to measure Iq.

    Just to make this clear, the OLD is TPS782, and the NEW is TPS782 as well. Where both devices bought from the same source?

    Have you tried an ABA swap? Perhaps just swapping the OLD to the NEW and the NEW to the OLD spots? I am wondering if there is any leakage happening and perhaps resoldering and/or cleaning the leads. The boards look good from the video but there still might be some residue. Also, is this the only device from the new lot that has been tested, or have other units been tested as well showing the same Iq? 

    The first device reads close to the .5uA Iq:

    and there shouldn't be any change on performance as the fabrication and test should be the same. 

    Best, 

    Edgar Acosta

  • in reply to Edgar Acosta1
    Prodigy 20 points

    Hi Edgar,

    Thanks your attention!

    Exactly, We bought TPS782 from the same source, just different time.

    We have already swap IC OLD and NEW, and the test result have no change.

    The boards we used are the new one. You can see on this video. We also try with the old board but still with the same result.

    We have also tested all reels (We bought 15kpcs in 5 reels) and all of them have the same result.

    We can't explain for this problem because the test results are always right.

    If available, We can send you some pcs of IC new for test Iq.

    Thanks.

  • in reply to Dylan Vo
    TI__Genius 12565 points

    Hi Dylan, 

    You are welcome. 

    I assume the devices where handled with care and the same way as the OLD IC, correct? 

    There is no reason for the IQ to change unless the devices are damaged. We would screen out any devices that do not meet the specs and then we would get a notice. 

    Before shipping samples to us, can you share with me the LOT information of these 5 reels? I would like to find any log files for those batches. Appreciate sharing this information and the patience. 

    Best, 

    Edgar Acosta

  • in reply to Edgar Acosta1
    Prodigy 20 points

    Hi Edgar

    I attached 2 images of LOT New and Old. 

    New: z3707711338242_b41e000c5f2c1762ca74884a88a8c4ce.jpg

    Old: z3707715185057_6f490fa751d7a15937dad638883381d3.jpg

    I don't know why the LOT information of the New LOT is deleted. It was deleted before we have received.

    Please help me check if you could.

    Many thanks

  • in reply to Dylan Vo
    TI__Genius 12565 points

    Hi Dylan, 

    Thank you for sharing this information with us. 

    Having the LOT and TKY information scratched is already very suspicious. 

    I looked at the OLD devices and I was able to track the information in our database and those devices are legitimate from TI. 

    However, I looked at the seal date from the NEW devices, and I noticed it says 06/27/21. I looked at all the Batches made in 2021, and there is nothing fabricated during May-June of 2021. Unfortunately, it seems to indicate that those are not legitimate TPS782 devices. 

    Please go to Anti-counterfeit | Quality policies & procedures | Quality & reliability | TI.com and fill out the  Counterfeit Validation Form. Make sure that when you fill this form, you take good quality of top and bottom of the devices and copies/pictures of the shipping information and the origin of where these devices where acquired. 

    Best, 

    Edgar Acosta