SN75LVDS83B: What is the difference bewteen CLKSEL= high and CLKSEL=low?

Eggsy Pang

Expert 4985 points

Part Number: SN75LVDS83B

Hi team,

My customer used two pcs SN75LVDS83B in their two boards, named Board_A and Board_B.

In Board_A, SN75LVDS83B CLKSEL= VIH, which mean rising edge input clock trigger.

In Board_B, SN75LVDS83B CLKSEL= VIL, which mean falling edge input clock trigger.

They Used the same LCD screen with LVDS interface to connect respectively with Board_A and Board_B.

The result is that:

1. The LCD with Board_B, show the Font size is average in screen.

2. The LCD with Board_B, show the Font size is uneven in screen, some word's Font size is Thicker than other word.

Do you have any suggestions?

Thanks!

over 5 years ago

0 Casey McCrea over 5 years ago

TI__Guru** 103215 points

Hello Eggsy,

In the results you say both tests were done with board B? I think it is a typo.

Anyways, the CLKSEL sets the rising or falling edge input trigger to determine where the data is sampled on the TTL input. Please check your input TTL source to determine which clocking scheme is used.

Best Regards,

Casey

0 Eggsy Pang over 5 years ago in reply to Casey McCrea

TI__Expert 4985 points

Hi Casey,

Yes, t is a typo.

Update:

The result is that:

1. The LCD with Board_B, show the Font size is average in screen.

2. The LCD with Board_A, show the Font size is uneven in screen, some word's Font size is Thicker than other word.

Why is the performance better when CLKSEL= VIL, ?

How to choose rising or falling edge input trigger depend on TTL input siganl like?

Thanks!

0 Casey McCrea over 5 years ago in reply to Eggsy Pang

TI__Guru** 103215 points

Hello Eggsy,

The CLKSEL should be selected based on the TTL source characteristics. Please consult the source documentation to understand whether the data should be sampled on rising or falling edge of the clock.

Best Regards,

Casey

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SN75LVDS83B: What is the difference bewteen CLKSEL= high and CLKSEL=low?