HD3SS3220: DIR pin termination

Takahiro Saito

Expert 5345 points

Part Number: HD3SS3220

Hi team,

Customer will not use DIR pin. In this case, is it okay to left DIR pin open?

Regards,

Saito

over 4 years ago

0 Takahiro Saito over 4 years ago

TI__Expert 5345 points

Hi team,

If the pull up is needed even when DIR pin is not used, could you explain how the pull up resistor is used inside of the IC?

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Saito-san,

Just to clarify the the customer is using I2C in this application, correct? If I2C is used and DIR is not used then pull up does not need to be installed. CABLE_DIR register should be read over I2C instead. DIR is an open drain output so a pull up is necessary to pull the pin high so that the output can be driven low. I do recommend reversing the pull up resistor for DIR in case debug is needed (pin can be probed).

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

Customer left DIR pin open and checked whether USB 3.0 communication is done correctly or not.

As a result, USB 3.0 communication is failed when the pull up resistor was not installed on DIR pin.

On the otherhand, they succeeded in USB 3.0 communication when the pull up resistor was installed.

Could you recheck whether DIR pin can be left open when this pin is not connected to other circuits.

I doubt that DIR pin is not only used for output to external circuit but also for input to the internal SS MUX.

If HD3SS3220 has a following circuit internally, it needs a pull-up resistor for proper operation.

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Satio-san,

After checking with design, DIR does need pull up and is used internally. Sorry for the confusion.

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

Thank you for checking it to designer.

Is the internal connection in the IC like the picture I attached in last thread?

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Saito-san,

Yes, you are correct.

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

Sorry for the reopen this thread.

But, customer is concerned about whether there are any pins that is similar to DIR pin such as the external pull up and pull down resistor is used in the IC. Are there any such pins on HD3SS3220? Particularly, doesn't CURRENT_MODE,VCONN_FAULT and ID pin uses external pull up or pull down resisistor in the IC?

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Satio-san,

This is correct, open drain output pins would need an external pull up resistor to operate correctly. Other pins that require external resistors include VBUS_DET, ENn_MUX, ADDR, ENn_CC, INT_N/OUT3, SDA/OUT1, SCL/OUT2.

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

Thanks.Let me clarify. Is it no problem for correct operation to left following pins float when these pin is not used?

1. INT_N/OUT3 in I2C mode

2. CURRENT_MODE

3. VCONN_FAULT_N

4. ID

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Saito-san,

I have answered in a per pin basis.

Needs external pull-up
Needs external pull-up
Does not need external pull-up if and only if Vconn fault is a no care for there customer.
Needs external pull-up

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

In figure 12, ID pin left open. Is it acceptable to left ID pin open for correct operation?

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Satio-san,

This is only in the case of a UFP application. In this case ID is not used to indicated connected.

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

2. CURRENT_MODE

-> Customer will set CURRENT_MODE through I2C. In this case, pull up isn't needed, correct?

3. VCONN_FAULT_N

-> Customer will read VCONN_FAULT through I2C. In this case, pull up isn't needed, correct?

4. ID

-> Customer will detect the attach through I2C. In this case, pull up isn't needed, correct?

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Saito-san,

2. CURRENT_MODE is an input and should be configured in cases where I2C is not available but is not required. CURRENT_MODE_ADVERTISE bit can be used instead (sub-address: 0x08).

3. VCONN_FAULT_N does not require a pull-up. Can be detected by VCONN _FAULT bit (sub-address: 0x09).

4. ID does not require a pull-up. Can be detected by ATTACHED_STATE bit (sub-address: 0x09).

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

You mentioned the pull-up resistor on DIR pin is used for internal circuit like below.

In this case, customer need to check the VIL and VIH for the internal USB-SS MUX.

Could you check the VIL and VIH for internal USB-SS MUX?

Based on your VIL/VIH information, customer will test whether the voltage on DIR pin meets the specification.

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Saito-san,

Why is customer checking this? Are they seeing some abnormal behavior with DIR pin?

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

No, they didn't see any abnormal behavior.

They want to check it because they are going to use 220kohm pull-up resistor although the datasheet recommends 200kohm pull up resistor.

Internal USB SS MUX should have a specification for the input to select the signal path. They concerned about if VIL/VIH specification is satisfied when they use 220kohm resistor instead of 200kohm resistor.

Can we guarantee that the internal selector signal for MUX meets the VIL/VIH specification when Vcc is within appropriate range and 220kohm resistor is used?

Regards,

Saito

0 Takahiro Saito over 4 years ago in reply to Takahiro Saito

TI__Expert 5345 points

Hi Malik-san,

Can I add one more question? How much is the required pull-up voltage range when 220kohm is used?

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Saito-san,

The recommended pull-up voltage is 3.3V. The 220Kohm should work with HD3SS3220, as long as DIR VOL spec of HD3SS3220 is satisfied.

0 Takahiro Saito over 4 years ago in reply to Malik Barton57

TI__Expert 5345 points

Hi Malik-san,

Is there any min-max value for 3.3V for pull-up?

Regards,

Saito

0 Malik Barton57 over 4 years ago in reply to Takahiro Saito

TI__Guru 64326 points

Hi Saito-san,

Since it is an open drain output there is really only a min value which can be calculated based on customer pull-up voltage, Vol of 0.4V and Iol of 1.6 mA. In this case min value of ~1.7 kOhms should be used but 200 kOhm is the recommend value.

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HD3SS3220: DIR pin termination