TPS650830: RESETZ output pin configuration?

Yoshwa

Expert 4050 points

Part Number: TPS650830

Hi team,

Customer inquired that he could not get a low level out for RESETZ in low-out logic state.

The RESETZ pin is defined as a push-pull output in the datasheet.

He got a low signal level when pulling up with a resistor, such as open drain.

What kinds of problems are considered?

over 6 years ago

0 Krishnamurthy Hegde over 6 years ago

TI__Expert 8730 points

Hi,

I have assigned your request to responsible Applications Engineer and we will get back to you as soon as possible.

Regards,

Murthy

0 Kevin LaRosa over 6 years ago

TI__Genius 17380 points

Hi Yoshwa,

My understanding is that RESETz is high when VIN > 5.4 V and LDO5 / LDO3 are operating correctly. If voltage drops below UVLO, RESETz will go low. Is customer not seeing that RESETz goes low when voltage drops below UVLO?

It is not clear to me why adding a pull-up would cause it to go low. What was the pull-up to?

0 Kenji Ohno1 over 6 years ago in reply to Kevin LaRosa

Genius 5095 points

Hi Kevin,

It is a phenomenon with my customers, so I will answer.
Although it is a peripheral circuit, the RESET terminal is directly connected to the microcomputer (input terminal).
Also, although it is a RESET terminal, it is the same for the evaluation board (TPS 650830 EVM).
When R127 (pull-up resistor) connected to the RESET terminal is removed, High output is not done.
Is there nothing wrong with the data sheet?

Best Regards,
Kenji /Japan Disty

0 Kevin LaRosa over 6 years ago in reply to Kenji Ohno1

TI__Genius 17380 points

Hi Kenji,

I think I understand now that the question is whether the RESETz signal is open drain or push pull? As you correctly noted the datasheet says push pull but the EVM suggests open drain, which matches your test.

I am currently investigating whether there is an internal setting which chooses between the two options or whether it is always open drain. Our device expert is out of office until next week but I am hoping to have more information by tomorrow.

0 Phil Yi over 6 years ago in reply to Kevin LaRosa

TI__Mastermind 49151 points

Hi Kenji,
RESETz signal is a push-pull output, no pull-up needed; if pull-up is not too strong, then the pull-up doesn't effect its working.
Please let's know if you still have more questions; otherwise, the e2e thread will be closed in next day.
Thanks!
Phil

0 Kenji Ohno1 over 6 years ago in reply to Phil Yi

Genius 5095 points

Hi Quote,

If R127 connected to RESETz of EVM is removed, High output is not done.

This is not push-pull, is not Open Drain?

Why is R127 attached?

Could you please confirm that R127 is removed from EVM you have?

EVM_RESETz　R127.pdf

Best Regards,

Kenji

0 Phil Yi over 6 years ago in reply to Kenji Ohno1

TI__Mastermind 49151 points

Hi, Kenji,

Double checked again on my EVM and confirmed that RESETZ is not a PP (Push-Pull) output, it's an OD (Open Drain) output. We'll make the correction in our next datasheet revision.

0 Kenji Ohno1 over 6 years ago in reply to Phil Yi

Genius 5095 points

Hi Phil,

Thank you for confirmation.
At the moment, please let me know if there are other mistakes in the data sheet.

Best Regards,
Kenji

0 Phil Yi over 6 years ago in reply to Kenji Ohno1

TI__Mastermind 49151 points

Hi, Kenji,
No other mistakes were found so far; I'll let you know in case we find others later or release of next update.

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TPS650830: RESETZ output pin configuration?