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LMX2571: Detailed Design Procedure

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Part Number: LMX2571

Hi all

Would you mind if we ask LMX2571?

There is the description on the data sheet P44 " Detailed Design Procedure ~ To use the direct digital modulation feature, put fractional denominator, DEN = 0."
Why should it set DEN=0 in case of direct digital modulation feature?
We are sorry that we could not find it.

Kind regards,

Hirotaka Matsumoto

  • Hello Matsumoto-san,

    Table 14 (R24) description for field "FSK_EN_F2" states:

    Enables FSK operation in all FSK operation modes. When this bit is set, fractional denominator DEN should be zero.

    Table 23 (R8) description for field "FSK_EN_F1" refers to the definition in Table 14, so the function of the F1 and F2 FSK enables is identical. If FSK is used with either F1 or F2, DEN should be zero.

    Compare this with the design in section 8.2.2, where no FSK is used and the device is only switching between F1 and F2. Table 43 shows the denominator is set to 1234567. If switching between F1 and F2 is the only requirement, and FSK is not enabled for either frequency, there is no restriction on DEN.


    Derek Payne

    Texas Instruments