LP8860-Q1: EMI Problem

Qianqian

Part Number: LP8860-Q1

Dear TI Expers，

I am now using LP8860A-q1 in display projects and failed the EMI conduction test in 80M/90M/100MHz~

Can you give me any advice about this?

We use near-field frequency spectrum to test the LP8860, we do find the 10MHz peak frequency and its harmonics, and VDD pin is affacted a lot~

I was wondering why the 10MHz frequency coupled to VDD pin?

And as is described in the datasheet, their is 10MHz internal Oscilator.

I diabled PLL and it does't make any sense.

over 6 years ago

0 Shirley He over 6 years ago

TI__Expert 5475 points

Hi,

We have an application note for EMI design guide of LP8860, as shown below. As you can see from Figure 61 and Figure 63, we also see large harmonic value at multiples of 10MHz. But with proper design which considers all the key points in the application note, the EVM can pass the EMI test easily.

www.ti.com/.../snva813.pdf

0 Qianqian over 6 years ago in reply to Shirley He

Genius 5010 points

OK,I got it~ Thank you very much~

0 Qianqian over 6 years ago in reply to Shirley He

Genius 5010 points

About the harmonic at 10MHz ， can you give me some advice on how to avoid it?
Cause I find the note for EMI design guide is mainly for the boost circuit~

0 Shirley He over 6 years ago in reply to Qianqian

TI__Expert 5475 points

Hi,

This is internal clock which is not easy to deal with. Since you mentioned VDD pin is coupled, can you try adding high frequency cap at the VDD pin?

0 Shirley He over 6 years ago in reply to Shirley He

TI__Expert 5475 points

Hi,

I'll close this thread due to inactivity. If you have more questions, just reply to it directly and it will open again. Thanks a lot.

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LP8860-Q1: EMI Problem