Hi Toms,

toms tao said:

after add 1K ohm resistor near to DS90LV011A chip, we can get normal output from SN65LVDT2

Could you help clarify what the resistor is connected to; while helping to share the schematics? Thanks.

Best Regards,

Michael.

Hi Michael

Thanks for you quickly replied.

Original we mounted R384&R387 with 0 OHM, Considering SN65LVDT2 have internal terminal resistor(110 OHM),so we did not R385 is non-pop.

but if R385 non-pop, LVDS receiver chip(SN65LVDT2)will be no output;after we put 1K with R385, we can get output waveform;  

Hi Toms

SN65LVDT2 has integrated internal impedance  but it can only be used in a point-to-point system or in a multi-drop system when it is the last receiver on the multidrop bus. Otherwise the change of bus impedance throughout the bus will result in multiple reflections and signal distortion.

It's hard to tell the application is correct with partial schematic. Please share the complete schematic with receiver (SN65LVDT2) included so we can help you better.

Thanks,

Yuan

please refer the application schematic, we also tried to remove C65&C66 on CIS board, but the issue still exists.

HI Michael

Thank you, it means that we mounted R385 with 1K ohm shoud be reasonable for impedance mismatch.

Can you share me which parameter is out of SN65LVDT2DBV spec. based on above waveform? we wanna to know if R385=1K ohm is suitable for this application.

pls:we also tried other values with R385,such as 100ohm/390ohm, but some of product can not work well,some of product can works well.

Thanks

Toms

Is it possible to check waveform and point out which one(rising time/fall time/holding time..etc) did not meet the part spec? we can know what is good design by signal check.thank you.

Hi Toms,

Could you help double confirm the impedance of the cabling? Thanks.

Best Regards,

Michael.

HI Michael,

we use normal FFC cable, did not do impedance control for this cable.

Do you say this cable should have impedance control for Clock signal?

LVDS Unlock Issue FA Report-To TI_20221026.pdf

Hi Michael

We tried change LVDS input voltage from 200mV to 500mV, the product function is OK, but we have three questions as below:

1.what is Input signal critical for normal output,--check the waveform, we can see the output with VIN=350mV, some of IT parts can have normal output waveform, but some of IC no output,why? 

2.why the output with 200mV/350mV input signal is normal pulse, but 500mv input signal is spike pulse output?

3.what is Eye pattern spec. for this part input signal?

Hello Toms,

To answer question 1 and 2, could you help us better understand what are the changes in each case 1-4?

3) For eye diagram patterns, input is usually generated by a Bit Error Rate Tester (BERT) that generates a PRBS pattern (typically 2^31 -1). The typical test conditions used below:

Input Differential Voltage = 200 mVpp

Vcm = 1V

tr=tf=0.5 ns (10% to 90%) 

Case1~4 means when we tested 13PCS CISM(CMOS Image Sensor Module),

some of CISM waveform shows as case 1(Vout=0 no output with Vin=200mV , Vout=0 no output with Vin=350mV,Vout=Spike pulse with Vin=500mV) ;

Some of CISM waveform shows as case 2 (Vout=0 no output with Vin=200mV , Vout=Spike pulse with Vin=350mV,Vout=Spike pulse with Vin=500mV) ;

Some of CISM waveform shows as case 3 (Vout=normal pulse with Vin=200mV , Vout=normal pulse with Vin=350mV,Vout=Spike pulse with Vin=500mV) ;

the output waveform as case4 is what we want; 

Sorry to make you confused, for LVDS schematic,please kindly refer the attached updated file,We used same one FFC cable+Same one Controller board with Option1(LVDS drive from SOC_U15) to test 13PCS CMOS Image sensor Modules; 13PCS CISM type is same, only serial number is different; but SN65LVDT2DBV output waveform on each CISM(CMOS Image Sensor Modules)is quite different as FA report shows. So I have two questions as below:

1.what is Input signal critical for normal output,--check the waveform, we can see the output with VIN=350mV, some of IT parts can have normal output waveform, but some of IC no output,why? 

2.why the output with 200mV/350mV input signal is normal pulse, but 500mv input signal is spike pulse output like case3?

 LVDS HW Structure-To TI_1028.pdf

Remark for hardware:the history is firstlly we use 200mV drive from SOC,we found some of CISM can not get normal output from SN65LVDT2DBV, so we tried to change to Option2,drive from external LVDS driver IC, but still have few CISM failed on no output;

So we changed back to option1 with 500mV drive from SOC, all of CISM have output waveform, but some of output is spike pulse,some if output waveform is normal pulse; we do not why this difference happen?how to judge the input signal quality is acceptable by SN65LVDT2DBV to generate normal output?

2) Can you replicate Case 2 and Case 3 with the 200mV input and capture the signal at R384 & R387 (CTL Board) and R41 & R42(CISM Board)? 

---case1~case4, we tested waveform based on LVDS signal drive from U15,not external LVDS driver IC U26.

Do you say we need to capcture waveform at R372&R373 for case2 and case3 with 200mV?

Help Toms,

My apologies, I initially thought the waveforms you shared were captured using the external LVDS driver. In that case, yes if you can replicate case 2 and case 3 with 200mV input and share the waveform at R372 & R373 and R41 &R42 that would be helpful. 

Regards,

Josh

Please kindly check the waveform as the attached fileLVDS Unlock Issue FA Report-waveform compare_1101.pdf

Hello Jusua

If you need to have more test for you view, please let me know.

Hello Toms,

Thanks for the waveform captures. I will take a look at them and respond later today.

Regards,

Josh

Hello Toms,

Thanks for your patience.

At the bottom of the waveforms capture, can you help me translate the wording? We have to make sure the input differential voltage going into the SN65LVDT2 is higher than +100mV and lower than -100mV. Figure 12 on the datasheet gives an example.

And just to double check, in both CISM boards is every component populated that same way? For instance C65 is populated on one board but not the other.

And just to double check, in both CISM boards is every component populated that same way?--Yes

For instance C65 is populated on one board but not the other.--No, C65&C66 is populated on everyLVDS Unlock Issue FA Report-To TI_1103.pdf CISM board.

Toms,

Is it possible to remove the SN65xx device on Case 3 and place it on Case 2 and try the measurements again?

Regards,

Josh