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TPS2065D: Input-output resistance is much to large

Hannes Ulbing
Prodigy 30 points
Part Number: TPS2065D
Other Parts Discussed in Thread: TPS2065

I have tested my prototype board with a TPS2065D on it.

T = 25°C; Vin = 5V; Rload = 10 Ohm; -> 500mA.

Referring to the datasheet, Rdson should have a value of 100 mOhm.

That results in an expected drop of 50mV between IN and OUT on the TPS2065.

I have 10 test candidates with following dropvoltage between IN and OUT on the TPS2065D:

  • 1x 75mV (150 mOhm)
  • 1x 90mV (180 mOhm)
  • 5x 150mV (300 mOhm)
  • 1x 200mV (400 mOhm)
  • 2x 300mV (600 mOhm)

None of the values is in the expected area. And many of them are very much larger than expected.

Is it possible that I have got a bad charge of TPS2065D?

Or what is the reason for these values?

  • 0
    TI__Expert 8980 points
    Hannes Ulbing ,

    Got your questions. How did you measure current? How did you measure voltage?

    Regards,
    Bob
  • 0 in reply to Bob Ma
    Prodigy 30 points

    Hi Bob,

    I measured the voltage on IN and on OUT with a multi-meter and also with the test adapter for testing the board in series production. I have a load on 10 Ohm and calculated the current values.

    I also measured the current value with a multi-meter.

    Regards Hannes

  • 0 in reply to Hannes Ulbing
    TI__Expert 8980 points
    Hi, Hannes,


    Did you use Kelvin Sense? The Vin voltage and Vout voltage should be measured at parts' pins.

    Regards,
    Bob
  • 0 in reply to Bob Ma
    TI__Expert 8980 points
    Hi, Hannes,

    Any updates of your case, have you get it resolved. I will close this thread if no more reply.

    Regards,
    Bob
  • 0 in reply to Bob Ma
    Prodigy 30 points
    Hi Bob,

    I spend much time in refining my measurement especially on the test adapter for the mass production.
    The results are quite the same. Non of them has a resistance between IN and OUT beneath 100 mOhm and the larges value is 640 mOhm.

    I also replaced one of these TPS2065D with a new part from the distributor. And this part had the expected result of 85 mOhm. So it really seems that we have got a bad series of parts or some fake parts for our prototype boards. These parts have been purchased by the manufacturer of the boards.

    Is it possible that TI produces such parts or are there fake parts on the market?

    Regards
    Hannes
  • 0 in reply to Hannes Ulbing
    TI__Expert 8980 points
    Hi, Hannes,

    This is interesting, we met this case before. There're fake parts on the market, they are not made by TI, they are made by other manufacture but marked TI logo.

    TI will test every parts before release to market. Only when the test results of parameters (like Rds_on) pass do we release the part on market.
    Please get the part from TI or regular distributor.

    Regards,
    Bob