TPS61021A: EN delay time

tateo yamashiro

Guru 10890 points

Part Number: TPS61021A

Hi,

We got a question from the customer about TPS61021A.
Could you help us?

[Question]
How much is the EN start-up and shutdown delay time?

They are considering the output discharge circuit. Is there any recommneded circuit?

Best Regards,
tateo

over 7 years ago

0 Youhao Xi over 7 years ago

TI__Guru* 78240 points

Hi Tateo-san,
Just let you know that the engineer supporting this part is currently on vacation. You may need to wait until early next week to get the answer.

Thanks,
Youhao

0 tateo yamashiro over 7 years ago in reply to Youhao Xi

Guru 10890 points

Hi, Thank you for your quick reply. We understood your current status. We look forward to your feedback.

Best Regards,

tateo

0 Helen chen over 7 years ago in reply to tateo yamashiro

TI__Mastermind 40080 points

Hi Tateo,

I'm back. Sorry for the delay. En delay during startup is around 150us. EN delay during turn-off is very short, only several us. and the Vo drop time is depend on the output cap and the load current.

What is the discharge time requirement in your application?

0 tateo yamashiro over 7 years ago in reply to Helen chen

Guru 10890 points

Hi, Thank you for your quick reply. They are considering the following discharge circuit. The output voltage is 3.3V and discharge resistor is 10 to 100ohm. They are concerned the discharge FET will be turned on while the IC is active. Is there better solution for this?

Best Regards,
tateo

0 Helen chen over 7 years ago in reply to tateo yamashiro

TI__Mastermind 40080 points

The logic is good. if EN keeps high level during on, then they need't worrid about the problem.

0 tateo yamashiro over 7 years ago in reply to Helen chen

Guru 10890 points

Hi, Thank you for your reply. When EN is turned off, if the discharge FET is turned on before the IC is shutdown, the load current will increse. They want to ensure the discharge FET is turned ON after the IC is shutdown. Is there any solutions?

Best Regards,
tateo

0 Helen chen over 7 years ago in reply to tateo yamashiro

TI__Mastermind 40080 points

In fact from EN low to IC turn-off delay is very short, within several us. that is once EN is low, the low side FET and the high side FET will trun off immediatelly. so the increase of the load current at that time has no effect to the IC. they can also add some RC delay to the discharge FET if they worried about the timing issue.

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TPS61021A: EN delay time