DS90UB928Q-Q1: Power Up Requirements

K.Yaita

Part Number: DS90UB928Q-Q1

Hi Team,

I have two questions about Power Up Requirements of DS90UB928Q-Q1.

(datasheet page 58)

1)
I believe VDDIO supply ramps more than 100us before VDD33 is no ploblem.
Is my understanding correct?
Or should I set "100us" exactly?

2)
Recommended condition shows "VDDIO < VDD33 + 0.3V".
Is it no ploblem to be "VDDIO > VDD33 + 0.3V" as long as during power up sequence?

(datasheet page 7)

Best Regards,
Yaita

over 8 years ago

0 K.Yaita over 8 years ago

Guru 29720 points

Hi

May I have your comments?

I would also like to know if there is leakage path from VDDIO to VDD33 because my customer found VDD33 ramped when applying VDDIO although he didn't apply VDD33.

Best Regards,
Yaita

0 Liam Keese over 8 years ago in reply to K.Yaita

TI__Genius 12705 points

Hello,
Yes, VDDIO more than 100us is correct, it does not need to be exactly 100us.
If there is concern about voltage bleed through, the supplies can be tied together.
PDB should remain low until the supplies are stable.

0 K.Yaita over 8 years ago in reply to Liam Keese

Guru 29720 points

Hi Liam-san,

I appreciate for your support.
How about question (2)?
Should I consider it is no ploblem to be "VDDIO > VDD33 + 0.3V" as long as during power up sequence?

I believe it is no ploblem but would like to confirm just in caase.

Best Regards,
Yaita

0 K.Yaita over 8 years ago in reply to K.Yaita

Guru 29720 points

May I have your comments?
I want just to tell my customer that internal currrent flow from VDDIO to VDD33 during power up sequence is no ploblem. (It doesn't damage the device itself.)

Just to tell you, my customer is using VDDIO=1.8V and VDD33=3.3V in his system.

Best Regards,
Yaita

0 Liam Keese over 8 years ago in reply to K.Yaita

TI__Genius 12705 points

Hello,
Is there any external loading on the VDD33 or just the 928 supply connection?

Liam

0 K.Yaita over 8 years ago in reply to Liam Keese

Guru 29720 points

Hi Liam-san,

I heard VDD33 supply isn't only used DS90UB928Q-Q1 itself.
I had a talk with my customer and he wants to know the following.

- If internal currrent flow from VDDIO to VDD33 during power up sequence could damage DS90UB928Q-Q1 itself or not.
- If there is workaround to prevent voltage bleed through(current flow) during power up sequence under VDDIO=1.8V and VDD33=3.3V condition.
*I heard it is impossible to be tied VDDIO and VDD33 together because of their system constraint.

Your support would be appreciated.

Best Regards,
Yaita

0 K.Yaita over 8 years ago in reply to K.Yaita

Guru 29720 points

My customer wants to know it immedeately because of his design schedule..
Your support would be really appreciated.

Best Regards,
Yaita

0 Liam Keese over 8 years ago in reply to K.Yaita

TI__Genius 12705 points

Hello,

I understand the urgency, but also we need to perform due diligence for any recommendation or correction to existing datasheet. Please expect response by 6/12

Regards,
Liam

0 K.Yaita over 8 years ago in reply to Liam Keese

Guru 29720 points

Hi Liam-san,

I really appreciate for your kind response.
I will have a talk to my customer and ask to wait a little more.

In addition, I put my e-mail address just in case.
yaita-k@clv.macnica.co.jp

Best Regards,
Yaita

0 K.Yaita over 8 years ago in reply to K.Yaita

Guru 29720 points

Hi Liam-san,

Is there any update about this issue?
I have to inform to my customer if it needs more time(days).

Best Regards,
Yaita

0 Liam Keese over 8 years ago in reply to K.Yaita

TI__Genius 12705 points

Hello,

Preference is for VDD33 to ramp up first to avoid VDDIO back drive to VDD33. It seems reason for datasheet conflict is due to PDB tied to VDD33 from RC circuit.
To support this use case woudl require system validation if it is OK for VDDIO to ramp up last, after VDD33 and PDB.

0 K.Yaita over 8 years ago in reply to Liam Keese

Guru 29720 points

Hi Liam-san,

My guess is both supplies (VDDIO and VDD33) can ramp at the same time but should checked if VDD33 isn't more than VDDIO is good solution.
If VDD33 > VDDIO is occured in power-up sequence, VDD33 should be slightly delayed from VDDIO as 100us that datasheet describes.
What do you think of this solution?

I still believe Power Up Requirements in datasheet page 59 isn't wrong.
http://www.tij.co.jp/jp/lit/ds/symlink/ds90ub928q-q1.pdf

Best Regards,
Yaita

0 Liam Keese over 8 years ago in reply to K.Yaita

TI__Genius 12705 points

Hello, if the current draw is minimal this should not cause damage to the device. We recommend for customer to perform validation at system level.

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DS90UB928Q-Q1: Power Up Requirements