TFP401A: Unsteady output pixel clock with no signal input

Justin Washburn

Part Number: TFP401A

Ive gone through several board iterations trying to solve this issue. When no input hdmi signal is present the odclock pin randomly switches from high to low. It only does it when the heat pad is soldered, grounded or not, when not soldered i do not see the pulse on the clock at all, the result is a white halo on a lcd screen after being disbaled for about ten minutes. Once powered cycled and signal presen the lcd will heal. When not soldered this issue does not occur regardless of no signal duration.

over 5 years ago

0 Ikechukwu Anyiam over 5 years ago

TI__Mastermind 35130 points

Hi Justin,

Can you share a scope shot of this behavior?

Regards,

I.K.

0 Justin Washburn over 5 years ago

Prodigy 100 points

Bottom is center heat pad soldered to gnd

0 Ikechukwu Anyiam over 5 years ago in reply to Justin Washburn

TI__Mastermind 35130 points

Hi Justin,

The bottom picture is actually expected behavior. The TFP401A's designed to have a free running clock output on ODCK with no input (1-2 MHz). The soldering shouldn't make a difference here, so it's strange that there's no output when the thermal pad is not soldered.

Regards,

I.K.

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TFP401A: Unsteady output pixel clock with no signal input