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SN54ACT244-SP: Output end circuit for 54ACT and 54HC tri-state

Part Number: SN54ACT244-SP
Other Parts Discussed in Thread: SN54HC595-SP

When building spaceflight hardware we had a cable that was mis-wired and applied voltage to the wrong pins. We need to do an analysis of where the current went to make sure we understood what happened to our hardware. Do you have a simplified end circuit diagram for tri-state outputs from an SN54ACT244-SP and a SN54HC595-SP?

  • Stephen, I do not have simplified circuit for the outputs.
    However, the absolute max tables can help define if you exposed the outputs to undue stress.
    Both devices have similar constraints.
    The ACT244 has abs max showing Vo constrained to -0.5 to VCC +0.5V
    It has an Iok spec of +/-20ma. This allows exceeding the Vo range if the Iok spec is observed.

    The HC595 does not spec Vo the same way. However, the result is the same as it has the same Iok specification.

    Thus, if current is limited to +/-20ma during the stress event then you are good.
    If the current was not constrained, and Vo was pulled lower than 0.5v below ground or greater the Vcc, then potential damage occurred.

    The specification is meant to protect the ESD structures to VCC and to GND. Going below ground or above Vcc will cause them to conduct. If the current it limited to less than 20mA, then the diodes will not be significantly stressed.
    Hopefully this helps.
    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade
  • Stephen,
    I see that this did not help you solve your issue.
    Could you provide more details on the exposure of voltages to pins and state(s) that the device was in during the exposure?
    Possibly a schematic with voltages noted?
    If this cannot be shared in public forum, let me know and I can reach out to you via email.
    Regards,
    Wade
  • Hi Stephen,

    As we have not seen activity on this thread and a request to move the discussion to email, I am closing the thread. If you have further questions please feel free to open a new thread.

    Thank you.