TMUXHS4212: Please provide guidance on the appropriate circuit values between devices for USB3.2gen2x1.

Hi,

Thank you for your question. 

Can you please provide your schematic? This would help clarify what you are proposing.

Best,

Stanton

It is part of the circuit diagram, but how should I attach the file (PDF)?

Hi,

Thank you for providing the schematic. I have reviewed and provided feedback below.

TUSB1002A – refer to schematic checklist

1. VCC: One 4.7 µF and one 0.1 µF capacitor on each VCC pin to GND
2. What is EN connected to (not visible)? EN should be left open or tied to 0.1uF cap to GND
3. TX2P/2N requires 0.1uF AC coupling caps
4. No need for pull down resistors R94, 95, 397,, 398
5. TUSB1002A is connected to an application processor, correct?
   1. please reference schematic checklist (included above) to read about RX AC coupling caps
6. Need to remove C108/109/110/112

TMUXHS4212 – refer to schematic checklist

1. Is TPD4E02B04 (ESD protection) needed?
2. Change C263/4/5/6 cap values to 0.1uF
3. Adding 330nf on B1P/N and C1P/N.

Let me know if you have any questions!

Best,

Stanton

Hello, Stanton.

[EN, SEL]
*TUSB1002A_SEL: The TYPE-C connector FLIP is detected by the PD controller and controlled by the FPGA in the same way as EN from the FPGA.

*TMUXHS4212_EN: The EN is controlled from the FPGA (USB3.2 IP).

The TUSB1002A_TX2P/2N is connected to the Intel_FPGA diff-I/O(0.9v) via an ACcap of 0.1uF.
(It was not indicated on the circuit diagram)

[TUSB1002A]
Is there anything other than 0.1uF for TUSB1002A_RX1P/1N?
I think the options are limited in the checklist.
I think 0.1uf is appropriate whether there is a DC bias or not.
(Using 0.22uf did not produce good results)

[TUSB1002A, TMUXHS4212]
Is it necessary to remove C108/109/110/112 only for the combination of [TUSB1002A, TMUXHS4212]?

I think TUSB1002A has a 1.8V DC bias on TX1P/N and RX2P/N, but is it really unnecessary to have an ACcap when using TMUXHS4212?

Is it necessary to remove pull-down resistors R94,95,397,and 398 because C108/109/110/112 are removed?

[TUSB1002A, TMUXHS4212 checklist and DATASHEET]
I have checked the checklist, but looking at the datasheets of each device,
I think there are several variations in the installation of AC coupling.
The circuit diagram shown earlier is a result of referring to the circuit configuration of combinations such as [TUSB1002 and HD3SS3220IRNHR] or [TUSB1002, HD3SS321], but both have ACcaps installed between the equalizer and redriver. Why?
(There is a similar description in the datasheet)

[TMUXHS4212]
Is it necessary to provide 0.33uF for B1p,B1n,C1p,C1n because DC bias removal is necessary when removing C108/109/110/112 of [TUSB1002A, TMUXHS4212]?

[ESD]
TPD4E02B04 (ESD protection) is necessary. Please let me know if you have any other recommended ESD devices.

I’m sorry for all the questions.

Thank you very much.

Hello, 

[TUSB1002A]
Is there anything other than 0.1uF for TUSB1002A_RX1P/1N? 0.1uF works (USB spec: 75-265nF for AC coupling caps).

[TUSB1002A, TMUXHS4212]
Is it necessary to remove C108/109/110/112 only for the combination of [TUSB1002A, TMUXHS4212]? You are correct. With the combination of TUSB1002A and TMUXHS4212, it is okay to remove C108/109/110/112 because C263/4/5/6 and adding 330nf on B1P/N and C1P/N will provide the ac coupling for TUSB1002A and TMUXHS4212. AC coupling caps on input and output of mux are added in series. AC coupling caps on input and output of redriver cannot be added in series.

Is it necessary to remove pull-down resistors R94,95,397,and 398 because C108/109/110/112 are removed? Whether you have C108/109/110/112 or remove them, pull-down resistors, R94,95,397,and 398, are not necessary.

[TUSB1002A, TMUXHS4212 checklist and DATASHEET]
The circuit diagram shown earlier is a result of referring to the circuit configuration of combinations such as [TUSB1002 and HD3SS3220IRNHR] or [TUSB1002, HD3SS321], but both have ACcaps installed between the equalizer and redriver. Why? AC coupling caps placement is flexible as long as total value is within USB spec (75-265nF).

[TMUXHS4212]
Is it necessary to provide 0.33uF for B1p,B1n,C1p,C1n because DC bias removal is necessary when removing C108/109/110/112 of [TUSB1002A, TMUXHS4212]? You are correct. I recommended removing C108/109/110/112 and adding 330nf on B1P/N and C1P/N because this is a simpler design for AC coupling than the alternative. If you choose to put AC caps on both sides of the mux (the alternative), then you must use external resistor termination network to restore the bias voltage (see Figure 9-1 (c) in the TMUXHS4212 datasheet).

[ESD]
TPD4E02B04 (ESD protection) is necessary. Please let me know if you have any other recommended ESD devices. TPD4E02B04 is good.

Let me know if you have any questions.

Best,

Stanton

Any update from your end? Please resolve if complete.

Best,

Stanton

Hello Stanton
Thank you for your concern.

After modifying the circuit board components with the recommended circuit settings you gave me last time, I checked and found that the communication quality did not improve and the number of errors increased slightly.

Since the above is due to the removal of resistors and replacement of capacitors, we are considering revising the circuit board.

(1) Circuit board revision with the addition of 0.22uf between the USB connector and MUX RXp/n of the circuit shown first.

(2) Circuit change to install a Retimer.

I’m sorry to ask this as an aside, but could you please advise me on how to implement (2) above?
------>
We will adopt Retimer (DIODES: PI2EQX22024). This will be installed on the USB connector side, then switched to the front and back of the connector by MUX, and finally connected to FPGA (Intel-Cyclone10GX).
(AC coupling will be installed between devices)
<------

**** TUSB1002A necessary between TMUXHS4212 and FPGA?

best regards

Hi,

Concerning revision consideration (1):

AC coupling on TX is required, but AC coupling on RX is not required.

Concerning revision consideration (2):

Have you considered using redriver + mux? For example, TUSB1042 (supports USB 3.1) and TUSB1142 (supports USB 3.2)? This would reduce the number of devices, increase convenience, and extend the reach of the signal.

Best,

Stanton

Hello Stanton
Thank you for your concern.

Regarding whether or not we have considered “TUSB1042 and TUSB1142”.
We have not considered it.
The Intel EVB-kit includes USB3.1 10Gbps, and after evaluating the circuit, we created a reference circuit board. Originally, the circuit used “TUSB1002 and HD3SS3220”, but We first created a circuit board with “TUSB1002A and HD3SS3212”. Due to difficulty in obtaining devices, we changed HD3SS3212 to TMUXHS4212I as an alternative and are currently using it.

best regards