TUSB1044: About internal MUX

Hideto-san

Is the customer configuring TUSB1044 using FLIP/CTL0/CTL1 in GPIO mode or FLIPSEL/CTLSEL in I2C mode? If not, then the switch between AUX and SBU is open and 1.7V on AUX probably is the leakage voltage from SBU.

Thanks
David

Hi David-san,

 

Thank you for your prompt reply.

 

Each pin are set by GPIO

DIR1：H　

DIR0：L　

CTL1：H　

CTL0：H　

FLIP：L

 

And, their measurement environment is as follows.

 

 

Could you please let us know if you have any information and concern?

 

Regards,

Kanemaru

Hideto-san

TUSB1044 configuration is correct, but the test setup is not valid. Per the DisplayPort CTS spec, the DUT shall be connected to a circuit equivalent to the respective counterpart of Figure 3-22 of the DP standard. For example, if the DUT is a Source, the test load shall be equivalent to the Sink portion of Figure 3-22. This equivalent circuit shall include any loading of the test equipment.

Below is Figure 3-22 copied from DP spec.

So you can not directly apply 3.3V to SBU1.

Thanks

David

Hi David-san,

 

Thank you for your prompt reply.

I understood that I can’t directly apply 3.3V to SBU1.

However, our customer would like to know the internal MUX circuit.

 

If they apply 3.3V to SBU1 pin, AUXp voltage is around 1.7V.

Is this correct behavior?

If yes, could you please let us know this reason?

 

Regards,

Kanemaru

Hideto-san

The common mode voltage for SBU1 is min of 0 and max of 0.4V. Applying 3.3V directly onto SBU1 exceeds this common mode voltage requirement, and place the mux into an non proper working state. I can't say whether 1.7V is the correct behavior of this non working state. But again, 3.3V should not be directly applied on SBU1.

Thanks
David

Hi David-san,

 

Thank you for the information.

I have two questions.

 

--------

[Q1]

We understand that if a normal MUX, 3.3V of SBU1 is observed on AUXp but they can’ observed 3.3V on AUXp.

Therefore, we guess that AUX RX affects 3.3V.

Is my understanding correct?

 

If yes, could you please let us know a detail reason (information)?

If no, could you please let us know other cause?

--------

 

[Q2]

We understand that a recommended range of SBU1 is from 0V to 0.4V.

However, they would like to know the maximum voltage that can pass the voltage.

Could you please let us know if you have any information?

 

For example,

0.4V is OK

・

・

1.5V is OK <= it is maximum voltage that can pass the voltage

1.6V is NG

・

・

3.3V is NG

--------

 

[Q3]

I understand that if Type-C receptacle is flipped, AUX channel DC common mode voltage is the following.

-0V to 0.4V @ Vcc=3.3V for AUXp and SBU2.

-2.7V to 3.6V @ Vcc=3.3V for AUXn and SBU1.

Is my understanding correct?

--------

 

 

< Background>

They understand that this usage is not recommended but they have to understand this reason.

Because, they are evaluating a unique usage.

Therefore, they would like to know about internal MUX circuit.

 

If you contact to below my e-mail address or let me know your e-mail address,

I can send the customer information.

I’m looking forward to hearing from you.

 

[my e-mail address]

Kanemaru-h@macnica.co.jp

 

Regards,

Kanemaru