TMDS171/TMDS181 3-level Logic Interface

Sadanori Kato

Other Parts Discussed in Thread: TMDS181, TMDS171

Hi,

The 3-level logic interface is applied for the pins of PRE_SEL, EQ_SEL/A0, TX_TERM_CTL and SWAP/POL.
I understood that these pins should be strapped to GND through 65kΩ if setting the logic low, be strapped to VCC through 65kΩ if setting the logic high.
So, why should 65kΩ resistor be applied as the pull-up or pull-down resistor ?
Could you please tell us that reason including the internal circuits ?

Best regards,
Kato

over 9 years ago

0 Moises Garcia over 9 years ago

TI__Mastermind 23815 points

Hi Sandanori,

The 65k resistors are required to set the proper voltage level due to internal biasing.
We can't provide more information about the internal circuits.

Regards

0 Sadanori Kato over 9 years ago in reply to Moises Garcia

Guru 36540 points

Hi Moises-san,

Thank you for your quick response.
I understood.

Best regards,
Kato

0 Sadanori Kato over 9 years ago in reply to Sadanori Kato

Guru 36540 points

Hi Moises-san,

I have obtained an additional question from our customer.
For instance, does TMDS171/TMDS181 work normally if using the resistors such as 47kΩ, 68kΩ and 100kΩ instead of the 65kΩ resistors ?
Could you please give me your advice about it ?

1. Case of 47kΩ as the pull-up/down resistors
OK or NG

2. Case of 68kΩ as the pull-up/down resistors
OK or NG

3. Case of 100kΩ as the pull-up/down resistors
OK or NG

Best regards,
Kato

0 Moises Garcia over 9 years ago in reply to Sadanori Kato

TI__Mastermind 23815 points

Hi Sanadori-san,

65k is the recommended value, we can guarantee the device will work properly.

If customer uses a different value, it may work but we can't guarantee it; if support is needed the resistor may be needed to go back to 65k for proper debugging.

Regards

0 Sadanori Kato over 9 years ago in reply to Moises Garcia

Guru 36540 points

Hi Moises-san,

Our customer would like to know the minimum and maximum value for the pull-up/down resistors.

So, could you please investigate it for them ?

Best regards,

Kato

0 Moises Garcia over 9 years ago in reply to Sadanori Kato

TI__Mastermind 23815 points

Hi Sadanori-san,

I have asked for minimum and maximum value, there is no such range.
Of course having similar resistor values will work, just keep as close as possible to 65k.

Regards

0 Sadanori Kato over 9 years ago in reply to Moises Garcia

Guru 36540 points

Hi Moises-san,

Thank you for your comment.
I will inform our customer of the information and contact with you if I obtain any questions from our customer.

Best regards,
Kato

0 Sadanori Kato over 9 years ago in reply to Sadanori Kato

Guru 36540 points

Hi Moises-san,

I have obtained an additional question from our customer.
Our customer would like to use the 47kΩ resistors as the pull-up/down resistors.
So, could you please recommend the 47kΩ resistors for TMDS171/181 ?
He would like to hope the low cost.

Best regards,
Kato

0 Moises Garcia over 9 years ago in reply to Sadanori Kato

TI__Mastermind 23815 points

Hi Kato-san,

We only recommend 65k, any other value is up to customers decision.
What they can do is to build one board using 47k, if it works fine they can venture going to mass production with that value, however as I mentioned before if problems are present and they require support from our side, those resistors will need to to be changed to 65k for proper debugging.

Regards

0 Sadanori Kato over 9 years ago in reply to Moises Garcia

Guru 36540 points

Hi Moises-san,

Thank you for your explanation.

Unfortunately, our customer hasn't been convinced yet.
So, could you please tell me the reason why the 65kΩ resistors are necessary and explain it in conjunction with a change of the internal threshold in more detail ?

Best regards,
Kato

0 Moises Garcia over 9 years ago in reply to Sadanori Kato

TI__Mastermind 23815 points

Hi Kato-san,

We can't disclose the internal operation of the circuit, 65k is the value that was used to set high/low level threshold.
If customer is not convinced, they can use the value that better fits their needs, however as I have mentioned before, only 65k is our recommended value, perhaps smaller values work too, but in case of debugging, only 65k will receive support.

Regards

0 Sadanori Kato over 9 years ago in reply to Moises Garcia

Guru 36540 points

Hi Moises-san,

Thank you for your strong support.

I will try to negotiate with our customer based on your response.

Best regards,
Kato

Interface

Interface forum

TMDS171/TMDS181 3-level Logic Interface