TFP401: Jitter in HSYC output at 1280 x 1024, 60 Hz

Masanori Tachibana

Part Number: TFP401

Hello support team,

I have a question about the DVI receiver TFP 401.
Jitter is appeared in the horizontal synchronous output signal of TFP401 48 pin (HSYNC terminal).
There is no jitter in other output signals.
Jitter only occurrs at specific frequency and specific resolution. (1280 x 1024 @ 60 Hz)

Question
As a cause of jitter, is there a possibility that the connection between the board and the thermal pad on the back side of the IC is weak?

Best regards,
M. Tachibana

over 6 years ago

0 Joel Jimenez0 over 6 years ago

TI__Mastermind 18655 points

Hi Masnsori,

I'm reviewing your question and will be providing feedback ASAP.

BR,
Joel

0 Joel Jimenez0 over 6 years ago in reply to Joel Jimenez0

TI__Mastermind 18655 points

What device are you using TFP401 or TFP401A? Could you swap the device with the TFP401A?

0 Masanori Tachibana over 6 years ago in reply to Joel Jimenez0

Genius 5350 points

Hello Joel-san,

Sorry, our customer is using TFP401A.

Best regards,
M. Tachibana

0 Joel Jimenez0 over 6 years ago in reply to Masanori Tachibana

TI__Mastermind 18655 points

Hi Masanori-san,

Sorry, my bad in the suggestion above. The only other difference between both devices is the “HSYNC Jitter Immunity” incorporated into the TFP401A. This was designed to compensate for early transmitters that did not have a stable HSYNC signal. There really isn’t a need nowadays for the HSYNC Jitter circuitry as this was mainly a problem with some devices back years ago. Hence, if your video source does not require the mentioned feature there may be a jitter added in HSYNC. Please, try swapping to the TFP401 and let us know if you get the same results.

Regards

0 Masanori Tachibana over 6 years ago in reply to Joel Jimenez0

Genius 5350 points

Hello Joel-san,

Thank you for your comment.

At first, what I want to know is whether or not the connection (like soldering) of the thermal pad of the IC to the board is related to HSYNC jitter.
Could you teach me whether they have a causal relationship.
The customer seem to suspect that HSYNC jitter is caused by poor soldering of thermal pad.

Best regards,
M. Tachibana

0 Joel Jimenez0 over 6 years ago in reply to Masanori Tachibana

TI__Mastermind 18655 points

Hello Tachibana-san,

Yes, this can be related. A poor connection of the thermal pad can produce electrical noise in the digital, analog, and PLL power-supplies this along with the accumulated jitter on the clock and data lines due to reflections and external noise sources generate data integrity issues.

I can provide you our reference PCB files through email if you want.

Regards

0 Masanori Tachibana over 6 years ago in reply to Joel Jimenez0

Genius 5350 points

Hello Joel-san,

Thank you for teaching me.
It is very helfpul for me.

I didn't know that the thermal pad was related to jitter.
I will inform this advice to our customer.

Best regards,
M. Tachibana

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TFP401: Jitter in HSYC output at 1280 x 1024, 60 Hz