TPS40055-EP: short circuit between pin 5 and pin 9

Hey Sheldon,

What is the biasing voltage of what you are using to measure the resistance between the two pins?

Often there is ESD protection diodes between the two grounds as an ESD requirement that can be forward biased by certain ohmmeters.

Thanks,

Daniel

Hey Sheldon,

If the meter has a bias voltage of 0.7 V then it is likely the ESD diodes bias on and you are measuring a short because of the diodes turning on.

If you try biasing under 0.5 V I believe you will not see the short.

Thanks,
Daniel

Hi Daniel:

Today we measured the resistance between pin 5 and pin 9 on two ICs of TPS40055-EP with two digital multi-meters in parallel mode, one dialed to RESISTANCE mode and another one dialed to mV DC voltage mode. In this way, the resistance is still measured to be 0.9 Ohm and DC voltage is 0.9 mV. By this method, you will see that the ESD diodes won't get biased on.

We could confirm that there is a very low resistance (<1 Ohm) between pin 5 and pin 9 of TPS40055-EP. Please verify this result with the design engineers of TPS40055-EP. Thank you

Sheldon

Hey Sheldon,

Thank you for the testing you have done.
I will track down the designers of this part and ask them this question.

This can take time so thank you for your patience.

Thanks,
Daniel

Hi Daniel:

Thank you for your help.

Sheldon

Hi Daniel:

Thank you very much for your answer. It correlates with what we measured on IC.

Sheldon