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DS26C32AT: Device failure

Rhea Gao
Expert 2580 points
Part Number: DS26C32AT

Hi，

I have customers who use this chip after mass always have problems, the failure rate is very high, and the corresponding motor wobbles after the galvanometer is powered on. Before the differential signal is transferred to the single-ended signal, the tvs device is added and the surge test is done. When the surge reaches a certain value, the parts are damaged.

Please help to analyze the reasons and give suggestions.

Many thanks!

schematic diagram：

  • 0
    TI__Guru 52062 points

    Hi Rhea,

    What level and duration of surge is being applied to the device?

    What is the clamping voltage when the devices fail? 

    Please let me know because right now - it is very possible that the protection scheme is not going to work - this is a not a surge rated IC so the surge cannot exist on teh A/B pins at all - so if the clamping is insufficient it could cause major issues. 

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Expert 2580 points

    Hi Parker,

    1. The surge duration is about 20us.

    2. The following is part of the report of the surge test for reference.

    Thanks~

  • 0 in reply to Rhea Gao
    Guru 316510 points

    The maximum ratings of the D5V0L2B3SO allow peak pulse currents of up to 6 A. Your tests exceed this.

    The absolute maximum ratings of the DS26C32AT allow input voltages of up to ±14 V. Your tests exceed this.

    As far as I can see, the D5V0L2B3SO can protect the DS26C32AT only for ±25 V surges. For larger surges, you need better protection.

  • 0 in reply to Rhea Gao
    TI__Guru 72521 points

    Hi Rhea,

    I agree with Clemen's comment. The DS26C32AT states the absolute maximum voltage it can handle is 14V while the testing looks like the devices are being subjected to higher than 14V. The external diodes you are using look like they handle a peak current of 6A and during a 6A peak current pull, they have a max clamp of up to 14V (11.5V typical). It seems like you will need to strengthen the external diode to something that can handle ~35A while clamping to a max of 14V instead of 6A at 14V.

    -Bobby

  • 0 in reply to BOBBY
    Expert 2580 points

    Hi  Bobby, Clemens,

    First of all, I am sorry that the customer feedback on the drawing of the post-protection device is actually used WS05DUC-B, rather than D5V0L2B3SO.

    Then the customer wants to test and check whether it is the damage caused by surge or the damage caused by high current. Do you have any good test suggestions?

    Thanks~

  • 0 in reply to Rhea Gao
    Guru 316510 points

    The WS05DUC-B is specified to clamp to 17 V (typ.), 20 V (max.) at 8 A. Like the D5V0L2B3SO, it is not strong enough to protect the receiver from voltages above 14 V.

    When the voltage is too high, the isolation breaks down, which allows a current to flow. The damage is caused by both voltage and current.

  • 0 in reply to Rhea Gao
    TI__Guru 52062 points

    Hi Rhea,

    As Clemens and Bobby have mentioned - the issue is the clamp and the WS05DUC-B is not strong enough for your tests - you need a stronger protection circuit protect the device. So the issue doesn't seem to be the DS26 device. 

    Best,

    Parker Dodson