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RF430F5978: RF430F5978 LF sensitivity issue.

Youngjoo Kim
Prodigy 10 points
Part Number: RF430F5978

Hi,

My customer has a question about tuning the LF antenna in RF430F5978.

They were made as shown in the schematic below.

They calculated the value by testing the receive sensitivity by changing the capacitors' capacity of each C16, C18, and C20. (Result - C16 : 86 pF, C18 : 100 pF, C20 : 90 pF)

The test results are as follows:

1) C16 : 86 pF, C18: NC, C20 : NC - Receive distance: 0 ~ 2.5 m

2) C16 : NC, C18: 100 pF, C20 : NC - Receive distance: 0 ~ 2.5 m

3) C16 : 86pF, C18: 100 pF, C20 : NC - Receive distance: 0 ~ 1.2 m

The results of the test show that when a capacitor is connected as shown in 1 and 2, it is received at 2.5 m, but the distance is shorter if connected as shown in 3.

Question :

Is there a problem with the way they test? If there is a problem, please tell me how to test it.

Can the software be used to tune the LF antenna in RF430F5978? If you can, please let me know how.

Best regards,

YJ.

  • 0
    TI__Mastermind 18265 points

    Hello YJ,

    3D-Antenna coils have mutual coupling between the three coils.

    Dependent on the coil manufacturer it is recommended to connect certain pins to a common ground to reduce mutual coupling.

    Please see also the recommendation from PREMO for the 3DC15.

    Therefore TI recommends to connect pin 1, 7 and 8 of 3DC15 to VCL pin of RF430F5978.

     

    Yes, the software can be used for resonance frequency trimming.

    Please see the RF430F5978EVM User Guide chapter 12 LF Antenna Trimming Tab:

     

    http://www.ti.com/lit/ug/slru007/slru007.pdf   

     

    Best Regards,

    Helfried