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MAX3232: cause of failure

Yuta Nishie
Genius 4955 points
Part Number: MAX3232

Tool/software:

Hi,

I think the following are the causes of IC damage.

・Short circuit of signal line
・Surge
・Noise

In case of MAX3232, if the IC is damaged due to the above reason, could you please tell me how it will behave?

After we shipped it as a finished product, it broke down at the customer (communication was not possible), so we are looking for the cause.

Best Regards,

Nishie

  • 0
    TI__Guru 72771 points
    Yuta Nishie said:
    ・Short circuit of signal line

    Short circuit would need to exceed 25V on receiver pins and 13V on driver pins. There can be multiple failure signatures but guess is short to GND/Vcc or/and V+/V- pins.

    Yuta Nishie said:
    Surge

    Fail signature would be similar to above. Surge is usually way more energy since this can result in kV level of voltage. I've sometimes seen the plastic get blown up from this type of event. Most times though, you may not see the damage physically by just looking at it. 

    Yuta Nishie said:
    ・Noise

    If within abs max of device, maybe just signal integrity issues. Like bits are occasionally wrong. 

    Other potential sources could be ESD if someone touches the connector pins or during hot insertion to a live cable, the insertion could cause overshoot/undershoot on the pin that temporarily exceed abs max ratings. 

    All EOS events can result in shorts to GND/Vcc/V+/V-.

    If the EoS event isn't too bad (not surge), then maybe V+ and V- rails start to deregulate and can't hold the VoH/VoL levels. (Signifies damage to the charge pump circuits).

    -Bobby

  • 0 in reply to BOBBY
    Genius 4955 points

    Hi BOBBY-san,

    Thank you for your support. It was helpful for you to explain the symptoms such as surge and short circuit.

    I sent the customer's circuit information by private message. I would appreciate it if you could check these and let me know the cause of the failure.

    Best Regards,

    Nishie

  • 0 in reply to Yuta Nishie
    TI__Guru 72771 points

    I'm posting my response on the e2e thread incase there are any issues with the e2e PM system..... 

    Hi Yuta, For future communication. You can email me at duynguyen@ti.com 
    e2e personal message is harder to keep track of and I may not respond if I don't see it. 

    "All devices are used at EU 400 V (with a transformer between them)."
    If you have a 400V signal with a transformer, it might be possible that the transformer is coupling some of the signal on to the RS485 bus. Particularly when you power up the 400V rail, the initial voltage swing up to 400V can cause a large voltage spike to appear on the RS485 bus for a short amount of time. I suspect this could be the reason for failure. You could also see a large spike when you power off the 400V rail for the same reason.

    With a design that involves a transformer, you may need to add additional protection like a TVS diode on the sides that may see the transients that are generated by the transformer. 

    Other possibility for damage is maybe GND shifts. Solution is basically the same, bi-directional TVS diode references the local GND.
    -Bobby

  • 0 in reply to BOBBY
    Genius 4955 points

    Hi Bobby-san,

    Thank you for your support.

    I will tell the customer what you told me. If I receive additional questions from the customer, I will send you an email.

    Best Regards,

    Nishie