DS90UB948-Q1: Open LDI output open wire failure

Shinji Tsuji

Part Number: DS90UB948-Q1

Hi team,

I am investigating the failure mode analysis of the case where D0- pin open failure.

I cut D0- wire at UB948 output, so termination resistor at Timing controller input side is still connected between positive and negative LVDS inputs of TCON.

Could you advise how is the TCON input signal looks like and what do you expect data to become?

Because I set LVDS bit mapping to JEIDA mode, D0- output is G - R7 - R6 - R5 - R4 - R3 - R2.

I think if D0- is disconnected, LVDS line is pulled High and all data in D0 channel becomes 1.

Is my understanding correct?

regards,

over 5 years ago

0 Casey McCrea over 5 years ago

TI__Guru** 103215 points

Hello Shinji,

It sounds like this question should be posed to the TCON vendor instead. Can you please consult your TCON vendor? Because this is not a device level question for 948

Best Regards,

Casey

0 Shinji Tsuji over 5 years ago in reply to Casey McCrea

TI__Genius 14119 points

Hi Casey,

I will contact TCON vendor, but could you advise how does the waveform looks like when D0- wire is disconnected while termination register exist?

regards,

0 Casey McCrea over 5 years ago in reply to Shinji Tsuji

TI__Guru** 103215 points

Hello Shinji,

Assuming the TCONN receiver is high impedance, then there will be 0V on the D0+ and D0- lines at the input to the TCONN. But we can not comment on the TCONN input pin structure

Best Regards,

Casey

0 Shinji Tsuji over 5 years ago in reply to Casey McCrea

TI__Genius 14119 points

Hi Casey,

Does it mean the Open LDI output will pull down to 0V?

Assuming TCON input is high impedance, I thought the Open LDI D0+ output drives TCON input High.

Could you explain the mechanism how D0+ and D0- will go 0V?

Does UH948 detect output status and shut down the output at open Output?

regards,

0 Casey McCrea over 5 years ago in reply to Shinji Tsuji

TI__Guru** 103215 points

Hello Shinji,

I understand your question now is about cutting only the D0- trace, not the D0+ trace also.

We only specify the LVDS driver output voltages under the condition that D0+/- are terminated with 100ohms which would not be the case in this condition.

But essentially the two +/- inputs of the TCON will be pulled to around the same voltage which is an undetermined condition. Please consult the TCON vendor regarding the state of the differential input when the receiver sees ~0V differential input

Best Regards,

Casey

0 Shinji Tsuji over 5 years ago in reply to Casey McCrea

TI__Genius 14119 points

Hi Casey,

Here is the case I consider.

Does UH948 D0+ keep output normal voltage?

Does the input of the receiver becomes 0V differential assuming input is high impedance?

LVDS disconnection failure.pptx

regards,

0 Casey McCrea over 5 years ago in reply to Shinji Tsuji

TI__Guru** 103215 points

Yes Shinji,

This is correct. Assuming the receiver is high impedance, the differential voltage should be 0V

Best Regards,

Casey

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DS90UB948-Q1: Open LDI output open wire failure