LM46002: Noise floor at low frequency

tateo yamashiro

Part Number: LM46002

Hi,

We got a question from customer about LM46002.
Could you help us?

[Question]
We found the reference design PMP9457 test report. We have question about figure 9 CISPR 22 test result. We can see the noise floor of the below switching frequency. We wonder why this noise floor is occurred. Could you tell us why this noise floor is occurred? And if there is solution for reducing this noise floor, please let me know it.

Best Regards,
tateo

over 7 years ago

0 Ambreesh Tripathi over 7 years ago

TI__Expert 6860 points

Yamashiro- san ,

There should be no subharmonic peaks coming out of the device . There may be some issue with noise floor itself . We will take the data on the EVM (without filter) again and get back to you soon .

---Ambreesh

0 tateo yamashiro over 7 years ago in reply to Ambreesh Tripathi

Guru 10890 points

Thank you for your reply. We look forward to your feedback.

Best Regards,

tateo

0 Ted Zhang over 7 years ago in reply to tateo yamashiro

TI__Intellectual 2280 points

Hi tateo

Below is what we test base on EVM. Picture 1 is the noise floor, picture 2 is the EVM test result with 3.3V output. As you can see there are no such subharmonic peaks coming out of the device. Hope this may help!

Ted Zhang

0 tateo yamashiro over 7 years ago in reply to Ted Zhang

Guru 10890 points

Hi, Thank you for your support. We understood no such subharmonic peaks coming out of the device. So is the noise floor at low frequency of PMP9457 coming out of input filter?

Best Regards,
tateo

0 Ambreesh Tripathi over 7 years ago in reply to tateo yamashiro

TI__Expert 6860 points

Yamashiro-san ,

I believe that the peaks that you see at subharmonics would already be part of the noise floor of the testing system .

---Ambreesh

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LM46002: Noise floor at low frequency