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TRF7962A: Crystal matching

rei
Mastermind 6135 points
Part Number: TRF7962A

Hi,

My customers have a question about the crystal matching of TRF7962A.
They are doing crystal matching test.

They tried C1 and C2 with two patterns, 22pF and 27pF.


In general, frequency will increase when the capacitance is small.
However actually measured, when the capacitance was small, the frequency became small.

In general, if the capacitance is small, the negative resistance will be large. However, when the capacitance was small, the negative resistance became small.
Customers can't decide C1 and C2 because it is different from the general behavior.

Does anyone know anything about this behavior of TRF7962A?

Regards,

Rei

  • +1
    TI__Mastermind 18265 points

    Hi Rei,

    I don't have an explanation for this behavior but the selection of he capacitors C1 and C2 has to be done to match the specified load capacitance if the the crystal and the stray / parasitic capacitance of the board. if this calculation is done correct the frequency should match the nominal 13.56MHz. Why is the customer testing with different capacitors? Do the have problems to reach the nominal frequency of 13.56MHz?

    Best Regards,

    Helfried