TPS51200 power supply sequence

Masazumi Ishii

Genius 3945 points

Other Parts Discussed in Thread: TPS51200

Hello

There is a question about TPS51200.

The power supply sequence is as follows.
　
power　up
VLDOIN→VIN
power　down
VIN→VLDOIN

Is it satisfactory at this power supply sequence?

The reason in the case of being useless?

Does IC break?

Thank you

over 13 years ago

0 Nancy Zhang over 13 years ago

TI__Mastermind 49470 points

Hi Masazumi,

There is no power sequence requirement for TPS51200. Your case is ok. The IC will not break.

Thanks,

Nancy

0 Masazumi Ishii over 13 years ago in reply to Nancy Zhang

Genius 3945 points

Hello Nancy

Thank you for the reply.

There is no power sequence requirement for TPS51200.

TPS51200　datasheet page10 power sequence requirement．

There is no sequence. Why is it OK?

Are there any application notes?

Thanks,

0 Nancy Zhang over 13 years ago in reply to Masazumi Ishii

TI__Mastermind 49470 points

Hi Masazumi,

The datasheet page 10 is TI recommended power sequence requirement. That is 3.3/2.5Vin applying first, then VLDOIN and when everything is ready to enable S3/S5. It would be fine if VLDOIN is present before 3.3/2.5Vin comes up since the entire LDO shuts down without any issue. We don't have any application notes for that. I recommend you could follow page 10 power sequence requirement.

Thanks,

Nancy

0 Masazumi Ishii over 13 years ago in reply to Nancy Zhang

Genius 3945 points

Hi Nancy

Thank you for Answer

Last week I received the reply from you.

`There is no power sequence requirement for TPS51200. Your case is ok. The IC will not break.`

Are you a reason for having drawn this reply?

I would like to use reference by design.
(power sequence. power up VLDOIN→VIN power　down VIN→VLDOIN. It cannot change. )

Thanks

0 Nancy Zhang over 13 years ago in reply to Masazumi Ishii

TI__Mastermind 49470 points

Hi Masazumi,

Yes, you can use your power up/down sequence. It will not break IC.

Thanks,

Nancy

0 Masazumi Ishii over 13 years ago in reply to Nancy Zhang

Genius 3945 points

Hi Nancy.

no power sequence for TPS51200.

Please let me know the basis of this.

I am sorry that I tell you the same thing repeatedly.

thanks.

0 Nancy Zhang over 13 years ago in reply to Masazumi Ishii

TI__Mastermind 49470 points

Hi Masazumi,

I already reply the basis of this in Jun, 25. We recommend the power sequence in the datasheet. However, if you go with your own power sequence, it should be ok without hurting the IC. That is all.

Thanks,

Nancy

0 Masazumi Ishii over 13 years ago in reply to Nancy Zhang

Genius 3945 points

Hi Nancy.

I checked the reply on June 25 of you again.

I am question.

'the entire LDO shuts down without any issue.'

What is the meaning of this?

Vin=0V is Shutdown. （whole LDO）

the whole LDO→Shutdown

Even if LDOIN exists ahead of VIN at this time, it is meant as OK？

Also it.　EN=L？

thanks.

0 Nancy Zhang over 13 years ago in reply to Masazumi Ishii

TI__Mastermind 49470 points

Hi Masazumi,

Vin is supply voltage for VTT LDO. If Vin=0V, the LDO will not start up even if LDOIN exists and no matter EN=H or L. So If LDOIN is ahead of Vin, it should be ok . You could order an EVM to verify this feature.

Thanks,

Nancy

0 Masazumi Ishii over 13 years ago in reply to Nancy Zhang

Genius 3945 points

Hi Nancy

Thank you for the reply.

I am question.

Vin=0V、VLDOIN=2.5V　

Doesn't current leak in IC from VLDOIN and doesn't it break IC ?

What is the basis on which IC does not break?

thanks.

0 Nancy Zhang over 13 years ago in reply to Masazumi Ishii

TI__Mastermind 49470 points

Hi Masazumi,

I will check with designer and get you back soon.

Thanks,

Nancy

0 Nancy Zhang over 13 years ago in reply to Nancy Zhang

TI__Mastermind 49470 points

Hi Masazumi,

I apologize for misleading you in previous posts. I test the EVM by applying VLDOIN first and then Vin. I could not find anything wrong with IC performance. Everything works properly. However, I talk to designer this morning. He said applying VLDOIN first before Vin is not recommended. When Vin=0V, the control circuits are not powered up. So the control circuits can not control the LDO output stage which is biased by VLDOIN. Depending on some internal leakage paths, the output stage may or may not turn on when Vin=0V and VLDOIN is powered up. The simulations can not tell us much because the device leakage currents are not well modelled. So we don't recommend this power sequence. Please follow the power sequence in the datasheet for your application.

Thanks,

Nancy

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TPS51200 power supply sequence