SN65DP159: 50 Omh Pullups on IN_D[2:0] and IN_CLK

Needhu Gunasegaran

Part Number: SN65DP159
Other Parts Discussed in Thread: TMDS181

Team,

Could you please answer my customer question.
I have a short question regarding to the SN65DP159. The chip (and also the DP159) has internal 50 ohm pullups for the input signals (IN_D[2:0] and IN_CLK). But what is the reason why there are additional external 50 ohm resistors on the evalboard?

Page 24 : http://www.ti.com/lit/ds/symlink/sn65dp159.pdf

Page 12 : http://www.ti.com/lit/ug/sllu225/sllu225.pdf

I added them also in my schematics, but now I don't want to create stubs with vias to connect the resistors, which are normally not needed.

Thank you in advance.

-Needhu

over 7 years ago

0 JMMN over 7 years ago

TI__Guru 60870 points

HI Needhu,

The external 50 ohm pullups are only for the HDMI test port, they are not needed for a DP++ input.

Regards,
JMMN

0 Needhu Gunasegaran over 7 years ago in reply to JMMN

TI__Intellectual 2890 points

Thank you :)

0 Needhu Gunasegaran over 7 years ago in reply to Needhu Gunasegaran

TI__Intellectual 2890 points

Hi,

Please see customer response below,

but I'am still not sure if I really need the 50ohm pull-ups and have to ask again. In the datasheet from the chips stands the same you wrote (point 9.3.5 on page 28): ... Display Port terminations are integrated.... external not required...

But for HDMI I will use the same inputs with normally the same integrated terminations?

Also stands in the datasheet from the evaluation board in point 2.5 on page 6, that the pull-up resistors are populated but not connected.

Does it mean I don't need external 50 ohm input pull-ups for HDMI?

Thank you.
-Needhu

0 JMMN over 7 years ago in reply to Needhu Gunasegaran

TI__Guru 60870 points

Hi Needhu,

The DP159 device is not intended for use with HDMI inputs, it is designed for ac-coupled DP++ inputs. The DP159 can support testing with HDMI inputs if the external 50 ohm pullups, but this is for evaluation only. If the customer needs to support HDMI inputs, we recommend the TMDS181 device instead.

Regards,

JMMN

0 Needhu Gunasegaran over 7 years ago in reply to JMMN

TI__Intellectual 2890 points

Thanks,
I will get back to you if I have further questions.

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SN65DP159: 50 Omh Pullups on IN_D[2:0] and IN_CLK