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ULN2003A: Regarding Device Failure During ESD Testing on ULN2003A

Kyohei
Expert 2331 points

Part Number: ULN2003A

Hi team,

Our customer is conducting electrostatic discharge (ESD) testing on the ULN2003A. During this testing, a failure of the ULN2003A has been observed.

Load: Relay
Phenomenon: When ESD is applied, the electrostatic discharge enters via the OUT pin, resulting in device failure.

We assume that the surge is entering through the path from OUT to COM (this is presumed to be the phenomenon described in Section 8.4, Power Supply Recommendations, of the datasheet).

When a 1 µF ceramic capacitor was added between COM and GND, the failure no longer occurred.

Questions:

  • Is there any issue from a circuit standpoint with adding a ceramic capacitor between COM and GND?
  • Although we do not recognize that the power supply is being applied to COM as described in Section 8.4, could you please advise if there are any recommended countermeasures?

Best regards,

Kyohei

  • 0
    TI__Mastermind 34830 points

    Hi Kyohei-san,

    1. What ESD standard is being applied to the OUTx pin?

    2. There is no issue with adding a 1uF capacitor between COM and GND.

    3. Connecting COM to the supply will help with ESD protection because the supply will absorb part of the ESD energy.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Expert 2331 points

    Hi Patrick-san,

    Thank you for your support.

    For this matter, the ESD standard confirmed in the electrostatic discharge test is IEC 61000-4-2 Class X.

    We also understand that adding a 1 µF capacitor to the COM terminal does not cause any issues.

    Would it be correct to consider that adding a 1 µF capacitor or a suppressor to the COM terminal is effective against ESD,
    in the sense that ESD applied to each terminal is absorbed by the COM terminal?

    Best regards,

    Kyohei

  • 0 in reply to Kyohei
    Expert 2331 points

    Hi Patrick-san,

    Thank you for your support.

    I would appreciate it if you could review the above.
    Best regards,
    Kyohei
  • 0 in reply to Kyohei
    TI__Mastermind 34830 points

    Hi Kyohei-san,

    Thank you for confirming the ESD standard. System-level ESD standards like IEC 61000-4-2 typically require external ESD protections.

    Connecting COM to a 1uF capacitor, TVS diode, or to the relay supply should be effective against ESD on the xC (output) pins.

    Additional ESD components may be needed for the xB (input) pins to survive an IEC 61000-4-2 pulse. However, the xB pins typically don't have connections to the external environment, so system-level ESD events are less likely to happen in the application.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Expert 2331 points

    Hi Patrick-san,

    Thank you for your support.

    We would like to ask for your assistance with an additional confirmation.

    As a result of the internal failure analysis, degradation of the characteristics between 7C–COM and COM–E was observed.
    Since the 7C terminal is unused and left unconnected, we assume that an electrostatic discharge (ESD) from the air may have entered via the 7C terminal, resulting in damage between COM and E.

    We would like to consult with you regarding the handling of unused xB and xC terminals.
    Is there any issue with connecting both xB and xC to GND (E) when they are not used?

    Best regards,

    Kyohei

  • 0 in reply to Kyohei
    Expert 2331 points

    Hi Patrick-san,

    Thank you for your support.

    I would appreciate it if you could review the above.
    Best regards,
    Kyohei
  • 0 in reply to Kyohei
    TI__Mastermind 34830 points

    Hi Hyohei-san,

    Connecting xB and xC to GND is acceptable if they are not used.

    Thanks,

    Patrick