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Revision 3.6

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AS3977

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

Calculate the Division ratio

(EQ 20)

1. If the fractional part is larger than 0.5

FRAC <15:0> =

N= whole numbered part of

(EQ 21)

The A-Counter is the rest of the Division and can be calculated by:

(EQ 22)

2. If the fractional part is less than 0.5

FRAC <15:0> =

N = whole numbered part of

(EQ 23)

The A-Counter is the rest of the Division and can be calculated by:

(EQ 24)

In case, the value of the A-counter is zero, the value of the A-counter has to be increased by M and the value of N has to be decreased by one

AC = AC + M

N = N - 1

(EQ 25)

In case, the N-counter is in the range from 16 to 31 and the value of the A-counter is less than N-counter-14:

INT <3:0> = N - 16

INT <7:4> = AC - 1

(EQ 26)

Note:

In case, no solution can be found for the wanted center frequency, it may help to modify the reference frequency or INT<8>.

9.8.3 FSK Deviation Setting and Frequency Trimming

The frequency resolution

calculated with following equation:

Δf =

<8> +

(EQ 27)

9.8.3.1 FSK Deviation Setting

The FSK deviation DF is given by the frequency resolution

Δf and the setting of DF<7:0> and can be calculated with the help of:

DF =

<5:0> . DM

(EQ 28)

The deviation multiplier DM is determined by the setting of DF<7:6> according to the following table:

DF<7:6>

DM

0 (00)

1

1 (01)

2

2 (10)

4

3 (11)

16

DR

f

RF

Pf

REF

⋅

------------------

DR

INT

DR

FRAC

+

==

DR

FRAC

2

15

⋅

DR

INT

6

–

()

M

-----------------------------

AC

DR

INT

6

–

() NM

×

–

=

DR

FRAC

1

+

() 2

15

⋅

DR

INT

7

–

M

------------------------

PINT

(

⋅

1

)

f

REF

2

16

----------

⋅

ΔfDF

⋅