TUSB4041I: There is some issue about Hub Input Supply Current.

Lian Wu

Genius 5250 points

Part Number: TUSB4041I

Dears:

From datasheet the VDD of Hub Inpurt Supply Current is 86 mA.

However, the test result is so higher than the data of datasheet, pls. see the below pictures.

Pls. give some advice about the issue, thanks！

over 8 years ago

0 Elias Villegas M. over 8 years ago

TI__Guru* 76130 points

Hello,
How is terminal SMBUSz connected? can you share your schematic?
Are you following the power up sequence?
What is the current measurement value?
Regards

0 Lian Wu over 8 years ago in reply to Elias Villegas M.

Genius 5250 points

Dear Elias:

Pls. refer the schematic and we are following the power up sequence.

And from the datasheet the VDD is 86mA, and the current test value is higher than 600mA.

Pls. help to give some suggestion about it!

Thanks a lot!

0 JMMN over 8 years ago in reply to Lian Wu

TI__Guru 60870 points

Please provide the schematic of the VDD33 and VDD regulators. Is the high current draw (600 mA) the inrush current only or is it consistent?

Regards,
JMMN

0 Lian Wu over 8 years ago in reply to JMMN

Genius 5250 points

Dear JMMN:

Many thanks for your reply.

Pls. refer the schematic of VDD33 and VDD regulators:

Many thanks!

0 JMMN over 8 years ago in reply to Lian Wu

TI__Guru 60870 points

Hello Lian,

Can you confirm the sustained current draw on the 1.1V rail? After the initial current spike?

Thanks,

JMMN

0 Lian Wu over 8 years ago in reply to JMMN

Genius 5250 points

Dear JMMN:
I checked with our customer, the current is inrush only after power on.
Pls. kindly give some suggestions.
Thanks a lot!

Luck Wu

0 JMMN over 8 years ago in reply to Lian Wu

TI__Guru 60870 points

Hi Lian,

Can you confirm the sustained current draw on the 1.1V rail? In the screenshot provided, it looks like you are showing the inrush current of the 2.5V rail? What other than the 1.1V LDO is being fed by the 2.5V rail? We don't see a inrush current spike in our lab. How muck bulk capacitance is on the 2.5V / 1.1V rails? The LDO datasheet only recommends 1uF, try decreasing the bulk capacitance at the LDO to reduce inrush current.

Regards,
JMMN

0 JMMN over 8 years ago in reply to JMMN

TI__Guru 60870 points

Hello Lian,

Is there any update on this issue?

Regards,
JMMN

0 Lian Wu over 8 years ago in reply to JMMN

Genius 5250 points

Hi JMMN:
Bulk capacitance is 22uf on the 2.5V/1.1V rails in the customer's board.

Thanks!
Luck

0 JMMN over 8 years ago in reply to Lian Wu

TI__Guru 60870 points

Hi Lian,

To reduce the in-rush current, they will need to either reduce the bulk capacitance (10 uF or 4.7 uF) on the power rail or switch to a soft start LDO.
Regards,
JMMN

0 JMMN over 8 years ago in reply to JMMN

TI__Guru 60870 points

Hi Lian,

Is there any update on this issue?

Regards,
JMMN

0 Lian Wu over 8 years ago in reply to JMMN

Genius 5250 points

Hi JMMN:

I have talked about it with customer, and they said they have tested it using 10uF, but there also had a current.

Do you have other advice?

Thanks!

Regards,

Luck

0 JMMN over 8 years ago in reply to Lian Wu

TI__Guru 60870 points

Hi Luck,

I have completed additional testing in our lab with a current probe, and I'm not able to duplicate the high current draw that the customer is seeing. After the initial 50 ms, what is the sustained current draw? Does the high current draw occur only on a Power On Reset or does it occur with a manual reset too?

Regards,
JMMN

0 JMMN over 8 years ago in reply to JMMN

TI__Guru 60870 points

Hi,

I will be closing this thread until the customer has an update.

Regards,
JMMN

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TUSB4041I: There is some issue about Hub Input Supply Current.