TUSB321AI: How to configure TUSB321AI under HOST only?

Hi Sophie,

SophieCY Chen said:

3) Pin 5 (VBUS_DET): Can it be set to NC?

If DFP mode is being used, which it looks like it is, this is okay.

SophieCY Chen said:

4) Pin 6 (VCONN_FAULT#): Can it be set to NC?

If VCONN_FAULT is not being used, this can be left NC.

SophieCY Chen said:

5) Pin 7 & Pin 8: NC

Okay.

SophieCY Chen said:

6) Pin 9 (ID): If the SOC does not need to detect this pin, can this pin be NC? Or can it be directly connected to the EN_N pin of the USB VBUS switch?

The ID pin must be used to control when VBUS is being sent. The ID pin should be PU to either 3.3V or 5V with a 200Kohm resistor, depending on what the switch uses, and connected to the enable of the USB VBUS switch. VBUS should only be enabled when the ID pin is low.

SophieCY Chen said:

7) Pin 11 (DIR): Connect to the "SEL" pin of the HD3SS3212I, with the path being Pull-up to... 3.3V with a 10-kohm resistor. 

Okay.

Pin configuration seems okay. What application is the TUSB321AI being used for here?

Thanks,

Ryan

Hi Ryan,

This device is intended for connecting external USB devices only; no PD (Power Delivery) is required. The onboard Type-C connector connects to the internal SOC USB 3.0 port (SOC Host only). Between the SOC and Type-C connectors, I used a TUSB322AI and an HD3SS3212I. I referred to page 12 of the TUSB322AI datasheet, but had questions about some pin settings, hence the initial inquiry about pin configuration.

Thanks,

Sophie

Hi Sophie,

Got it, understood. Since you are using both the TUSB321AI or TUSB322I and HD3SS3212I, I would actually recommend giving the HD3SS3220I a look. This device acts as both a CC controller and SS mux, and may help to cut down on space.

Thanks,

Ryan

Hi Ryan,

Correction: I used "TUSB321AI" & HD3SS3212I just as the datasheet recommends.

HD3SS3220I ==> Thanks for your suggestion.

Sophie

Hi Ryan,

According to the datasheets for TUSB321AI and HD3SS3212I, please answer the following questions:

Q1: When connecting CC1 & CC2 of TUSB321AI to a USB-C connector, is swapping always necessary?

Q2: In Figure 3 of the TUSB321AI datasheet, why is the polarity of the SS signal reversed for CxP and CxN connected to the HD3SS3212 in the USB-C connector? (Because BxP and BxN in the figure do not have PN reversal.)

Q3:  Is pin 11 "DIR" of the TUSB321AI defined as follows:

DIR = H: When a voltage level change is detected on pin 2 "CC2"

DIR = L: When a voltage level change is detected on pin 1 "CC1"

Sophie

Hi Sophie,

SophieCY Chen said:

Q1: When connecting CC1 & CC2 of TUSB321AI to a USB-C connector, is swapping always necessary?

For specifically with the HD3SS3212, CC1/CC2 are swapped to minimize the crossing of the SS signals:

SophieCY Chen said:

Q2: In Figure 3 of the TUSB321AI datasheet, why is the polarity of the SS signal reversed for CxP and CxN connected to the HD3SS3212 in the USB-C connector? (Because BxP and BxN in the figure do not have PN reversal.)

For ease of routing, to ensure the signal does not need to be crossed. USB3 supports polarity swapping, so there is no issue with swapping P/N.

SophieCY Chen said:

Q3:  Is pin 11 "DIR" of the TUSB321AI defined as follows:

DIR = H: When a voltage level change is detected on pin 2 "CC2"

DIR = L: When a voltage level change is detected on pin 1 "CC1"

Correct.

Thanks,

Ryan