• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 46 subscribers
  • Views 551 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TVP5158 EMI Emission Problem

Swapnil Kanani
Prodigy 140 points
Other Parts Discussed in Thread: TVP5158

Hi,

We are using TVP5158 in one of our design. We have prototype board with us and conducted Radiated emission test on our design.

Test Observations:

System is failing at 81MHz frequency. We have 2 crystal and one oscillator of 27MHz. We have disconnected all the 27MHz source except the one connected to TVP5158. We observed that emission at 81MHz remains at the same level.

Design Details

1) We have used ABM10-27.000MHZ-E20-T(Abracon corporation) for TVP5158 frequency input

2) We have separate ground VSSA and VSS. Both VSSA (Analog Ground) and VSS(Digital Ground) are shorted with Ferrite bead (BLM15AX601SN1D) which has 600E impedance at 100MHz.

Queries:

1) Is it necessary to connect XTAL_REF(pin 100) of TVP5158 through 0E resistor to VSSA? TVP5158 datasheet says that pin 100 is internally connected to analog ground. EMI results shows improvement after disconnecting pin 100 from analog ground

2) When we remove ferrite bead between analog ground and digital ground, we see improvement in EMI results. Please suggest best way to isolate Analog and digital ground

Please also let us know any additional measure in layout apart from the layout guidelines for TVP5158.

Best Regards,

Swapnil Kanani

 

  • 0
    TI__Genius 16810 points

    Swapnil,

    On the TVP5158EVM, we ran a trace from the XTAL_REF pin to the crystal circuitry and the made a connection to ground at the crystal circuitry.  The connection to ground at the crystal may not be an absolute requirement.  Did you make this connection to analog ground?

    Did you disable the 27M oscillator output druing your test?

    Do all digital clocks and data traces have uninterrupted ground plane underneath the traces?

    Disabling the TVP5158 output ports and clock output might provide addtional information on the noise source.