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ULQ2003A-Q1: Equivelent device without free-wheeling diode.

Shinu.V.Mathew
Expert 7465 points
Part Number: ULQ2003A-Q1

Hi Team,

 My customer is using ULQ2003AQDRQ1 for relay drive. ULQ2003 has a inductive kickback suppression diode for all outputs, all cathodes are shorted and provided as a single pin. There are some failure modes due to short mode failure of those free wheeling diodes which is a cause of concern.

Could you please help with any other relay driver without the freewheeling diode but with the same footprint? Since customer card is ready they cannot change the layout.

Thanks for the help and support.

Regards, Shinu Mathew.

  • 0
    TI__Genius 10855 points
    Hi Shinu,

    Unfortunately all of our 7-CH low side switches have the freewheeling diode. Can you elaborate on the issue that the customer is experiencing? Under what conditions are the freewheeling diodes being shorted?

    You could also include an external freewheeling diode in parallel to the internal one. If VIN is also going negative, an external TVS can also help protect the diode structure.

    Thanks,
    Arthur Huang
  • 0 in reply to Alpha H
    TI__Expert 7465 points
    Hi Arthur,

    Thanks for the reply. Will get back with details.

    Regards, Shinu Mathew.
  • 0 in reply to Shinu.V.Mathew
    TI__Expert 7465 points
    Hi Arthur,
    In an application one of those diodes failed in short mode and that driver is commanded. The relay coils connected to all other drivers in ULQ2003 gets a path to gnd when one of those drivers are commanded due to the internal short.

    Regards, Shinu Mathew.
  • 0 in reply to Shinu.V.Mathew
    TI__Genius 10855 points

    Hi Shinu, 

    I wanted to follow up here, any updates from the customer? Do we know under what conditions the internal diodes get shorted?

    Thanks,

    Arthur

  • 0 in reply to Alpha H
    TI__Expert 7465 points

    Hi Arthur,

    The device are working @ 26VDC and driven by 3.3V to activate actuators. Random channel failure observed, one of the internal diode fails during operation and affecting operation of all other channels.

    Regards, Shinu Mathew. 

  • 0 in reply to Shinu.V.Mathew
    TI__Genius 10855 points

    Hi Shinu, 

    Are there any waveforms that the customer can share? I'd be interested in seeing if the inductive kickback is causing damage to the device. 

    If so, you could add an external TVS to the inputs of the device, which should help prevent the inputs from dipping below 0V. You could also add an external flyback diode that can handle larger transient events. 

    Thanks,

    Arthur