ADS7841 State of digital output pins

na na78

Guru 16770 points

Other Parts Discussed in Thread: ADS7841

According to the datasheet, the digital inputs can be over-voltage tolerant up to 5.5V, regardless of VCC.

So, we think it is acceptable to apply 5V to digital input pins when VCC =0V.

How about digital output pins (DOUT, BUSY)?

We are assuming the impact of capacitive load CL as follows.

What is the state of digital ouput pins when VCC=0V?
Is that acceptable?

BestRegards

over 9 years ago

0 na na78 over 8 years ago

Guru 16770 points

Hi

I'm sorry to trouble you but hope to hear from you as soon as possible.

BestRegards

0 Abhijeet Godbole over 8 years ago in reply to na na78

TI__Expert 5575 points

Hi Na na

sorry for delayed reply

Digital pins are tolerant up to 5.5V irrespective of VCC condition so I think it should be fine. But I will still check internally and let you know about your specific use case.

Thanks & Regards
Abhijeet Godbole

0 na na78 over 8 years ago in reply to Abhijeet Godbole

Guru 16770 points

Hi Abhijeet

Thank you for your help.

I'm looking forward to hearing from you.

BestRegards

0 na na78 over 8 years ago in reply to na na78

Guru 16770 points

Hi Adhijeet

Did you have a result?
I hope you inform us about the current status.

Thanks.

BestRegards

0 Abhijeet Godbole over 8 years ago in reply to na na78

TI__Expert 5575 points

Hi Na na

Sorry for the delayed reply. This is fairly older part so its bit difficult to dig out device documents.. We are trying to carry this particular test on ADS7841 samples. I am awaiting ADS7841 samples as of now.

I will reply you as soon as I finish testing these devices.

Thanks & Regards

Abhijeet Godbole

0 na na78 over 8 years ago in reply to Abhijeet Godbole

Guru 16770 points

Hi Adhijeet

Thank you for your support!
I understand current status and I'm looking forward to hearing from you.

BestRegards

0 Abhijeet Godbole over 8 years ago in reply to na na78

TI__Expert 5575 points

Hi Na na

I have checked the use case you mentioned previously. With Vcc=0V I applied 5.5V to DIN (pin 14). ADS7841 digital pin can take up to 5.5V when Vcc=0. I did not see current spike flowing in to digital pin under this test condition.

Thanks & Regards

Abhijeet Godbole

0 na na78 over 8 years ago in reply to Abhijeet Godbole

Guru 16770 points

Hi Adhijeet

Thank you for your confirmation.

I understood it is acceptable that applying 5.5V to "Digital Input" pins with Vcc=0V from your result.

But in addition, I want to confirm if "Digital Output" pins can accommodate applied voltage (> 0v) when Vcc=0v, as shown in my first question.

Is there problem if we have capacitor at "Digital Output"(DOUT, BUSY)?

BestRegards

0 na na78 over 8 years ago in reply to na na78

Guru 16770 points

Hi Abhijeet

I would appreciate if you could reply.

Thanks.

0 Abhijeet Godbole over 8 years ago in reply to na na78

TI__Expert 5575 points

Hi Na Na

Digital pins as such should withstand 5.5V when Vcc =0. I have tested this on couple of device. You can confirm the results from your side if you get chance to test some devices.

Capacitance on digital pins should not affect functionality as far as delays introduced by it doesn't affect measurement errors. 100nF seems pretty high pin capacitance. Can you clarify why there is so much capacitance on digital pins

Regards

Abhijeet

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ADS7841 State of digital output pins