TPS25830A-Q1: Question about using external LDO

Yuta Kurimoto

Part Number: TPS25830A-Q1
Other Parts Discussed in Thread: TLV766-Q1

Hello Team,

I plan to use TLV766-Q1(Adj Vout) for the external LDO of TPS25830A-Q1.

The datasheet says the External LDO should be enabled after the TPS25830A-Q1 is enabled. The External LDO should be disabled before the TPS25830A-Q1 is disabled.

However the datasheet also mentions that we can tie the EN of external LDO and EN of TPS25830A-Q1 together.

I'm confused little bit about this. Is it saying that powering up/powering down the both external LDO and TPS25830A-Q1 simultaneously is acceptable?

Thanks,

Yuta Kurimoto

over 3 years ago

+1 Bob Ma over 3 years ago

TI__Expert 8980 points

Hi, Yuta-san,

Your understanding is correct, powering up/powering down the both external LDO and TPS25830A-Q1 simultaneously is acceptable.

Bob

0 Yuta Kurimoto over 3 years ago in reply to Bob Ma

TI__Genius 10630 points

Hello Bob,

I got further question from customer.

Could you please let me know the detail timing requirement of both EN of external LDO and TPS25830A-Q1?

The start-up time of LDO depends on the part number. If they use fast LDO which start up time is faster than that of the TPS25830A-Q1 internal VCC LDO, it may not meet the power up timing requirement. This is the reason why customer want to know the detail timing requirement.

Regards,

Yuta Kurimoto

0 Yuta Kurimoto over 3 years ago in reply to Yuta Kurimoto

TI__Genius 10630 points

Hello Bob,

This is kindly reminder. Can you please provide the answer?

Thanks,

Yuta Kurimoto

+1 Bob Ma over 3 years ago in reply to Yuta Kurimoto

TI__Expert 8980 points

Hi, Yuta-san,

Sorry that I missed you question. Below is EN VCC timing of TPS2583x. Please make sure LDO start up not faster than VCC. Let me know if any further questions.

Meanwhile, I will check with team how strict the timing requirements is.

0 Yuta Kurimoto over 3 years ago in reply to Bob Ma

TI__Genius 10630 points

Hello Bob,

Thanks for sharing the waveform.

Once you can get the timing requirement, please let me know.

Regards,

Yuta Kurimoto

+1 Bob Ma over 3 years ago in reply to Yuta Kurimoto

TI__Expert 8980 points

Hi, Yuta-San,

I didn’t get more detail on this requirement, please just make sure Vcc start up faster than LDO. Thank.

Bob

0 Yuta Kurimoto over 3 years ago in reply to Bob Ma

TI__Genius 10630 points

Hello Bob,

I got some additional question.

Q. In case the LDO is faster than the VCC start up, what is expected to be happen?

Q. Regarding with the waveform, how much is the slowest value of VCC start up?

Thanks,

Yuta Kurimoto

0 Bob Ma over 3 years ago in reply to Yuta Kurimoto

TI__Expert 8980 points

Hi, Yuta-san,

Q1. Will you apply EN before supplying VIN?

Q2. The waveform shows the slowest value, it doesn't change much in different status.

Bob

+1 Bob Ma over 3 years ago in reply to Yuta Kurimoto

TI__Expert 8980 points

Hi, Yuta-san,

Here's a supplement for your first question. Our designer were concerned the LDO regulator and 83x internal LDO regulator would fight each other, they afraid if external LDO is supplied before internal LDO, the internal VCC may not power up smoothly. If customer worry external LDO power up faster than internal LDO, I think they can use a GPIO to enable external LDO later than 830A.

Does customer need VBUS short to battery protection? If they don't need VBUS short to battery, I can recommend a Vconn supply with pFET scheme for customer.

Bob

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TPS25830A-Q1: Question about using external LDO