TLIN1028-Q1: Capacitor for unused Vcc

Akito Tabata

Intellectual 2630 points

Part Number: TLIN1028-Q1

Hi team,

When Vcc is not used, is a capacitor required?

Regards,

over 2 years ago

0 Eric Hackett over 2 years ago

TI__Guru 74252 points

Tabata-san,

Yes, a capacitor is still needed because nRST and TXD are internally pulled up to VCC, and the output capacitor is needed to stabilize the internal LDO.

Regards,

Eric Hackett

0 Akito Tabata over 2 years ago in reply to Eric Hackett

TI__Intellectual 2630 points

Eric-san,

Thank you for reply. I understand. What is the recommended value for capacitor on unused VCC?

Regards,

0 Akito Tabata over 2 years ago in reply to Akito Tabata

TI__Intellectual 2630 points

Hi Eric-san

I have additional question.

Could you provide Typ value of tpwr(Power-up time)?

Regards,

0 Eric Hackett over 2 years ago in reply to Akito Tabata

TI__Guru 74252 points

Tabata-san,

1uF to 4.7uF will work for the output on VCC.

We don't have a typical value in our characterization data that I can find for tpwr. I'll talk to our design team, but why do you need this value?

Regards,

Eric Hackett

0 Akito Tabata over 2 years ago in reply to Eric Hackett

TI__Intellectual 2630 points

Hi Eric-san,

Thank you for your reply.

I'll ask my customer why this value is needed and tell you later.

I'm sorry to ask you so many questions. Could you provide the state of pin in Unpowered system(Vsup < UVsup) like Table 9.1 of the datasheet?

0 Eric Hackett over 2 years ago in reply to Akito Tabata

TI__Guru 74252 points

Tabata-san,

I will have a reply for you by tomorrow, thanks for your patience.

Regards,

Eric Hackett

0 Akito Tabata over 2 years ago in reply to Eric Hackett

TI__Intellectual 2630 points

Hi Eric-san,

Could you please reply?

Regards,

Tabata

0 Akito Tabata over 2 years ago in reply to Akito Tabata

TI__Intellectual 2630 points

Hi Eric-san,

The reason my customer needs typ value of tpwr is that they expect the sum of the every typ value when actually measure whole wake up time.

Regards,

Tabata

0 Eric Hackett over 2 years ago in reply to Akito Tabata

TI__Guru 74252 points

Tabata-san,

Sorry for the delay here, I still haven't gotten a value for the typical value of tPWR, sorry for the delay on this.

If the system is unpowered, all pins will be high impedance, with their leakage values listed in the datasheet. Please let me know if you need to know more specific information.

Regards,

Eric Hackett

0 Akito Tabata over 2 years ago in reply to Eric Hackett

TI__Intellectual 2630 points

Hi Eric-san,

Please let me know when you get the typical value of tPWR.

Thank you for your answer. I could understand that all pins will be high impedance in unpowered situation.

Regards,

Tabata

0 Eric Hackett over 2 years ago in reply to Akito Tabata

TI__Guru 74252 points

Tabata-san,

I will update this thread when I receive more information about tPWR.

Regards,

Eric Hackett

+1 Danny Bacic over 2 years ago in reply to Akito Tabata

TI__Mastermind 26806 points

Tabata-san,

The tPWR value is not specified with a typical value due to its wide variance. Our test data has shown this varying, but always less than 2 ms. We have seen the power-on process finish as quickly as a few microseconds, but we have also seen it take longer than 1 millisecond. In general, it might be okay to estimate around 1 ms, but it depends on why they need it. Per above, you mention that they are using it for estimating whole wake-up time. If they want to do worst-case analysis for longest possible wake-up time, then they should use 2 ms. If they're just trying to get an idea of what it might be, then you could roughly estimate 1 ms with the understanding that it could be ±100% of this estimate across all corners.

Best,

Danny

0 Akito Tabata over 2 years ago in reply to Danny Bacic

TI__Intellectual 2630 points

Hi Danny-san,

Thank you for your detailed explanation. It is so helpful.

Regards,

Tabata

Interface

Interface forum

TLIN1028-Q1: Capacitor for unused Vcc