SN65DSI84-Q1: what is the function of 0X1B register?

Sherry Liang

Part Number: SN65DSI84-Q1

Dear team,

Recently my customer did the EMC test of our chip. At the beginning, the test can't pass. They try to change 0x1B register value, but no use. After setting 0X19[bit6=1], the test can pass. Could you please tell me why we create 0x1B register? What application do I need to adjust this register?

Thanks & Best Regards,

Sherry

over 4 years ago

0 Ikechukwu Anyiam over 4 years ago

TI__Mastermind 35130 points

Hi Sherry,

The setting of this register depends on your display panel. The panel will typically accept either 1.2V or 0.9V common mode voltage.

Regards,

I.K.

0 Sherry Liang over 4 years ago in reply to Ikechukwu Anyiam

TI__Genius 10255 points

Hi I.K.,

Thanks for your reply!

I understand the specs of 0.9V and 1.2V, but I still don't understand what application do I need to adjust 0x1B register?

In addition, do you know why changing 1.2V to 0.9V will improve the EMC performance?

Thanks & Best Regards,

Sherry

0 Ikechukwu Anyiam over 4 years ago in reply to Sherry Liang

TI__Mastermind 35130 points

Hi Sherry,

You only need to change it if the display panel datasheet specifies support for only 0.9V common mode voltage.

Lower voltage will naturally improve EMC performance as it will reduce voltage peaks.

Regards,

I.K.

0 Sherry Liang over 4 years ago in reply to Ikechukwu Anyiam

TI__Genius 10255 points

Hi I.K.,

Thanks for your reply!

I got it. Some panels' common mode are not exact 0.9V or 1.2V, for example, common mode is 9.5V. In this way I need to set bit 5:4=11, right?

Thanks & Best Regards,

Sherry

0 Ikechukwu Anyiam over 4 years ago in reply to Sherry Liang

TI__Mastermind 35130 points

Hi Sherry,

There's no way an LVDS panel will have a 9.5V common mode requirement. But yes you can adjust register 0x1B to try and meet panel specs. Typically this will not be needed as most panels are 1.2V.

Regards,

I.K.

0 Sherry Liang over 4 years ago in reply to Ikechukwu Anyiam

TI__Genius 10255 points

Hi I.K.,

Thanks for your reply!

I wrote a wrong value. It should be 0.95V instead of 9.5V.

0.9*(1+6%)=0.954V

Thanks & Best Regards,

Sherry

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SN65DSI84-Q1: what is the function of 0X1B register?