TPD4E001

Alex Kupchik66

Prodigy 175 points

Other Parts Discussed in Thread: TPD4S009, TPD4E001

What is the allowed safe safe of continuous current through an ESD diode?

Alex

over 8 years ago

0 Guy Yater over 8 years ago

TI__Genius 12190 points

Hi Alex,

For the TVS diodes in our product line we don't characterize them in this fashion. I can, however, be quite sure that the current is on the order of 1 mA to 10 mA.

Regards,

0 Alex Kupchik66 over 8 years ago in reply to Guy Yater

Prodigy 175 points

Thank you,

What is possible failure mode for the TVS diode, assuming continues current at levels higher than 10 mA.

Regards,

Alex

0 Guy Yater over 8 years ago in reply to Alex Kupchik66

TI__Genius 12190 points

Alex,

It can fail as an open or short with no predictability.

Rgds,

0 Alex Kupchik66 over 8 years ago in reply to Guy Yater

Prodigy 175 points

Great. Thank you.

i have a few follow up questions:

1. Can a 40 ms exposure to a continues current flow be a long enough to damage the part

2. Can be the same assumption applied to the ESD protection of the SN74LVC2G07DCKR. I guess outputs are ESD protected. There is possibility, in our implementation, for a feedback power flowing through the ESD diodes.

Alex

0 Guy Yater over 8 years ago in reply to Alex Kupchik66

TI__Genius 12190 points

Your questions
1. My responses

1. Can a 40 ms exposure to a continuous current flow be a long enough to damage the part

a. This would be dependent on the amount of current, it would need to be very small

2. Can be the same assumption applied to the ESD protection of the SN74LVC2G07DCKR. I guess outputs are ESD protected. There is possibility, in our implementation, for a feedback power flowing through the ESD diodes.

a. Can I see a schematic and a description of the source of the feedback?

Thanks,

0 Alex Kupchik66 over 8 years ago in reply to Guy Yater

Prodigy 175 points

No problem.
if it is possible I would like to send schematic to you personal attention.

Alex

0 Alex Kupchik66 over 8 years ago in reply to Alex Kupchik66

Prodigy 175 points

ESD.pdf

0 Alex Kupchik66 over 8 years ago in reply to Alex Kupchik66

Prodigy 175 points

Hi,

I have sent schematic, ESD.pdf. A feedback flow is possible from the AIO_ signals via the DA002 or U64, U65 , if the have build in ESD on their outputs, into the VCC_P3v3A. AIO_ signals can be pulled up to a local 3.3V up to 40 ms before the VCC_P3v3A become active.

Alex

0 Guy Yater over 8 years ago in reply to Alex Kupchik66

TI__Genius 12190 points

Hi Alex,

Okay, I see the issue. The solution is to use the TPD4S009. It is designed to prevent this. There is a blocking diode arranged so that no current will flow with up to 5.5V applied to any data protection pin (these are called IOx on TPD4E001 and Dx in TPD4S009) before any voltage on VCC appears. This is unique to TPD4S009 in our product line. Below I have circled the blocking diode that will prevent the current flowing.

Anything else?

0 Alex Kupchik66 over 8 years ago in reply to Guy Yater

Prodigy 175 points

Great, Thank you.

Let's say the TPD4E001 is not populated.

1. Can the feedback current flow via the SN74LVC2G07DCKR's ESD at the output ?

Alex

0 Guy Yater over 8 years ago in reply to Alex Kupchik66

TI__Genius 12190 points

Alex,

Let me rephrase the question to be sure I understand you: While U64 or U65 are unpowered by VCC_3P3VA, will a voltage on the AIO_signals cause the ESD cells in U64 or U65 to breakdown and sink current?

If this is the case, then no it is not a problem. Based on the Absolute Maximum ratings for those pins, the voltage applied to any output in the high-impedance or power-off state must fall between -0.5V and 6.5V.

0 Alex Kupchik66 over 8 years ago in reply to Guy Yater

Prodigy 175 points

Thank you,

Alex

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