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TPS74401: Clarification of Max. Rating and Recommended Condition

Ella KIM
Expert 4212 points
Part Number: TPS74401
Other Parts Discussed in Thread: TPS56C230,

Hi team,

Could you please help me to clarify the Absolute Max. Rating and Recommended Operating Condition spec.?

I can see VEN as an example. If a voltage below -0.3V is applied to EN pin, it may cause permanent damage to the device. And a voltage above 0V is recommended for EN pin. What about the voltage in the range of -0.3V ~ 0V? There inevitably exists the voltage in the range of -0.3V ~ 0V due to undershoot etc. and customer wants to clarify :

1. How to interpret this voltage range - is it within the normal operation?

2. If it's not within the normal operation, how long is this voltage level accepted not to damage the device?

It's even more confusing for customer because other devices such as TPS56C230 puts the same voltage level for both spec.

Thanks,

  • +1
    TI__Mastermind 37065 points

    Hello,

    The -0.3V is due to the forward voltage of the internal ESD diodes.  Once you drop below a schottky diode drop below ground (which is about 0.3V below ground) you will forward bias the ESD diodes.  While these diodes do protect against ESD events, these events are usually very short.  Line transient conditions or steady state are usually much longer than compared to ESD events.  For that reason you do not want to drop below -0.3V on the input.   

    You can operate at -0.1V, -0.2V, etc, however there may be additional leakage through the ESD diode as the diode is slightly forward biased, however this is not enough voltage to fully turn on the diode.

    "Recommended" operating conditions usually provide a small buffer against the Abs Max operating conditions to give some margin against exceeding abs max.  I'm not sure why the TPS56C230 lists the Recommended minimum voltage and abs max voltage as the same.  We can send this question to the group that owns that device if needed.  It is possible that the ESD diodes used in that device have more margin than the ESD diodes used in the TPS74401.

    Thanks,

    - Stephen