LM3880 / Incomplete Power-Down Sequence

S.Satoshi

Hi,

Please let me know the variation in 120ms at Incomplete Power-Down Sequence. I know it can't be guaranteed but is it almost the same variation with timer delay which is +/-15% or +/-20%?

Best Regards,

Sonoki / Japan Disty

over 8 years ago

0 Mathew Jacob1 over 8 years ago

TI__Expert 5900 points

The variation will be much lower. As you know delays in digital systems are fixed. A 400us variation in timer for 2ms Td will give 20% variation whereas for a 120ms time the variation will be less than a 1% for the same variation.

0 S.Satoshi over 8 years ago in reply to Mathew Jacob1

Guru 21675 points

Hi Mathew,
Thank you for your response. I understand that the variation should be 400usec just for reference.
Best Regards,
Sonoki

0 S.Satoshi over 8 years ago in reply to S.Satoshi

Guru 21675 points

Hi Mathew,

Please let me ask one more question.

I tried to change Enable from low to high after FLAG1 went low, then I could not see incomplete power down and also could see power up after fixed duration after EN low. The duration is not specified in datasheet but it was approx. 245msec at LM3880EVM. I could see normal power up after this 245msec. Can you try this on your bench and confirm the design spec of this duration?

LM3880 Not incomplete power down and normal power up.pdf

Fig1

Fig2

Best Regards,

Sonoki

0 S.Satoshi over 8 years ago in reply to S.Satoshi

Guru 21675 points

Hi Mathew,

Please let me know if you need more information. Your response will be appreciated.

Best Regard,
Sonoki

0 Mathew Jacob1 over 8 years ago in reply to S.Satoshi

TI__Expert 5900 points

Satoshi-san,

Let me look into this.

Mathew

0 S.Satoshi over 8 years ago in reply to Mathew Jacob1

Guru 21675 points

Hi Mathew,

Your continuous support will be appreciated. What I'd like to know is the duration we need to wait to power up normally after EN goes low.

Best Regards,
Sonoki

0 Tim Reyes over 8 years ago in reply to S.Satoshi

TI__Expert 3920 points

Hi Sonoki-san,

Yes you are correct, the time duration is fixed. See below scope shots to illustrate the behavior.

Regards,

Tim

0 S.Satoshi over 8 years ago in reply to Tim Reyes

Guru 21675 points

Hi Tim,

Thank you for evaluation result. From our result, It needs to wait 250msec to start normal power-up after EN goes Low. Is my understanding correct?

Best Regards,
Sonoki

0 Tim Reyes over 8 years ago in reply to S.Satoshi

TI__Expert 3920 points

Sonoki-san,

Yes you are correct. From EN going Low to the first flag coming up is about 250ms.

Tim

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LM3880 / Incomplete Power-Down Sequence