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TCAN2451-Q1: RE test

Ivy Jin
Expert 4675 points
Part Number: TCAN2451-Q1


Tool/software:

Hi team,

1. The customer found a 668.5kHz frequency during RE testing. From the datasheet there is no such switch frequency, may I ask what may be the cause of this issue?

The low frequencies were tested separately and found frequency radiation in the 330Khz, 660Khz and 1Mhz. 

2. In addition, the customer configured the register at 2.4MHz switch frequency, but the actual tested frequency was only about 1M, what could be the reason for this?

Thanks in advance!

Regards,

Ivy

  • 0
    TI__Guru 52552 points

    Hi Ivy,

    I think I am also emailing your customer as I got those images today from them as well. 

    Are they measuring the switching frequency at the switch node? If not can they please measure at the VCC1 node and measure the frequency of the ripple - the switch node is very sensitive and I don't want the probe interfering with the measurement (there still could be a problem - but I just want to eliminate any potential issue). 

    Also what is the difference in test setting for the spectrum graphs - I am asking because the second one shows clear spikes at 1MHz, 2MHz (which would match with the 1MHz you are seeing) -but the first picture doesn't really show the 1MHz - so I am wondering what the difference in testing is. I was able to speak to our systems team and they think it could be the buck converter doing frequency foldback if the VSUP voltage > 24V - so what is the input voltage looking like? 

    If you could get me the picture of the layout of the buck converter - improper buck layout could result in bad EMI testing results (both RE and CE). 

    On the 668KHz figure - do they have CAN communication active and if yes - what is the data-rate? 

    Please let me know - if you prefer we can simplify this thread as I think you may be working with a Ray - as I got the same exact question emailed to me from him - so if you want me to combine the email with you, him, and myself that could get everyone on the same page - but just let me know. 

    Best,

    Parker Dodson