TUSB4041I-Q1: TUSB4041I upstream pull-up and downstream pull-down

Carlos Sampaolesi

Part Number: TUSB4041I-Q1
Other Parts Discussed in Thread: TUSB4041I

Hello, I am migrating a product based on the TUSB2046B to the TUSB4041I.

In my investigation of the previous product (using the TUSB2046B) I found recommendations about the use of series resistors due to impedances and a pull-up for the definition of the speed in the upstream, as well as recommendations on the placement of a pulldown at downstram ports.
But now referring to the TUSB4041I I have not been able to find information regarding those three points and I wonder if this is because they are not necessary.

So I ask the following questions regarding TUSB4041I:

1) Is it necessary to place series resistors from 22 to 33 ohm in the upstream port?

2) Is it necessary to place a pull-up on the D + line of the upstream to set the speed in high-speed?

3) Do I need to place pull-down resistors on downstream ports?

over 5 years ago

0 David (ASIC) Liu over 5 years ago

TI__Guru**** 177796 points

Hi,

Those resistors and the edge control capacitors are internal in the Hub. The upstream 1.5K pullup is also internal in the hub. and the downstream 15k pulldown is also internal in the hub. So you don't need to implement these resistors when designing in TUSB4041I.

Thanks

David

0 Carlos Sampaolesi over 5 years ago in reply to David (ASIC) Liu

Prodigy 40 points

Hi David and thanks for your quick response.

I was able to test the hub without using the external resistors and it works perfectly.

I would like to take the opportunity to see if you recommend the use of external EDS portions as well as filters in  the upstream and downstream ports.

BR.

0 David (ASIC) Liu over 5 years ago in reply to Carlos Sampaolesi

TI__Guru**** 177796 points

Hi,

USB2.0 spec requires that all host and self-powered hubs must implement overcurrent protection for safety reasons. You can take a look at this e2e blog for the USB2.0 ESD implementation: https://e2e.ti.com/blogs_/b/analogwire/archive/2015/03/25/how-to-protect-usb-host-ports-with-esd-current-limit-protection-devices.

Thanks

David

0 Carlos Sampaolesi over 5 years ago in reply to David (ASIC) Liu

Prodigy 40 points

Hi David, I would like to ask you one more question regarding this topic. Could you tell me the pull-up resistance value on the GRSTN pin. Thaks!

0 David (ASIC) Liu over 5 years ago in reply to Carlos Sampaolesi

TI__Guru**** 177796 points

Hi,

Typical value is ~22k for the pull-up resistor on the GRST pin.

Thanks

David

0 Carlos Sampaolesi over 5 years ago in reply to David (ASIC) Liu

Prodigy 40 points

Excelent, Thanks for all your helps!

BR.

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TUSB4041I-Q1: TUSB4041I upstream pull-up and downstream pull-down