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TPS54335A: Confirmation of shipping test method

Dice-K
Mastermind 7470 points
Part Number: TPS54335A

Hi support team,
There is something I would like to confirm because a product with the TPS54335ADRCR has a defect in the inspection process.

【Questions】
1. Do you set a switching frequency of 480kHz (TYP) for the shipping test?
2. How many volts is the VIN input voltage in the shipping test to check the Vout output voltage?
3. Please let me know whether the PH output pin and other input/output pins have internal protection diodes (+, - direction).
4. The faulty device has about 10Ω between PH output and GND.
In this case, will it be rejected in the shipping test?

【Situation】
1. Device:
・TPS54335ADRCR
2. Operating conditions:
・VIN = 18V, Rrt = 100kΩ setting, switching frequency ≒ 480kHz (TYP), VOUT = 3.3V setting
3. Trouble occurrence:
・In-house shipping inspection process_substrate failure
・N = 1 unit (4 similar defects occurred in the past, 5th)
4. Bug details:
・DC-DC converter: 2_PH output abnormal waveform observed. (intermittent oscillation)
・Vout voltage output does not rise to 3.3V, only 1.5V..
・An overcurrent occurs and it falls into the current limit mode.
・After determining that the DC-DC converter was defective and replacing the parts, the output of Vout = +3.3V was normalized.

Regards,
Dice-K

  • +1
    TI__Genius 16632 points

    Hi Dice,

    All of parts will pass ATE tests to make sure the device parameters within datasheet Electrical Characteristics range.

    From your description of failed unit, seems PH-pin was short to ground, so low-side FET short and broken. Is this failure at device first start-up? Or after some time operation? Did you hot-plug or ESD tests before the failure happened? Any EOS risks during your tests?

    In e2e forum, what I can do is to review your schematic/layout/waveforms. But I cannot proceed FA process. Please contact TI local CQE team to move forward the case. Thanks.

  • 0 in reply to Miranda Gu
    Mastermind 7470 points

    Hi Miranda,
    Thank you for your reply.

    Perhaps, this is failure at device first start-up.

    Would the answer to the question be?
    1. Tested because there is a description of 480kHz in "Switching Characteristics".
    2. VIN tested at 4.5V ,12V and 28V from "Electrical Characteristics".
    3. The presence or absence of an internal protection diode is not disclosed.
    4. If it is 10Ω, it will be rejected in the "Low-side switch resistance" test.

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    TI__Genius 16632 points

    Hi Dice,

    1. 480kHz is typical value, our ATE tests use a range to decide pass or fail, not using one typical value.

    2. EC table values are based on full-loading range, unless otherwise noted, as shown below.

    3. Internal ESD diode may fail in your case, as you detected PH-GND short damage.

    4. Low-side FET short parts can NOT pass our ATE test.

    Suggest you to reach local CQE team to move forward FA process.

  • 0 in reply to Miranda Gu
    Mastermind 7470 points

    Hi Miranda,
    Thank you for your reply.

    I have understoodd about "4.".
    Are "1"to "3" the following?

    1. Tested with Rrt=100kΩ setting, switching frequency=384kHz~576kHz.
    2. Tested Vout with VIN = 4.5 to 28V.
    3. The PH pin has a protection diode. Other pins unknown.

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    TI__Genius 16632 points

    Hi Dice,

    ATE test is different with board tests. It will let device enter a special mode then sweep these parameters.

    Customers don't need to know the details. In short, the device fsw and Rds_on should follow datasheet EC table specs, this is verified by ATE test.

    Please contact local CQE team to take over this case.