AK1546 Datasheet, PDF (11/39 Pages) Asahi Kasei Microsystems – 3GHz Low Noise Integer-N Frequency Synthesizer

[AK1546]
8. Block Functional Descriptions
1. Frequency Setup
The following formula is used to calculate the frequency setting for the AK1546.
Frequency setting (external VCO output frequency) = F_PFD × N
Where :
N
F_PFD
P
B
A
: Dividing number N = [ (P × B) + A ]
: Phase detector frequency F_PFD = [REFIN] pin input frequency / R counter dividing number
: Prescaler Value (See < Address2>:{Pre[1:0]})
: B (Programmable) counter value (See <Address1>:{B[12:0]})
: A (Swallow) counter value (See <Address1>:{A[5:0]})
Calculation example
The output frequency of external reference frequency oscillator is 10MHz, and F_PFD is 200kHz and VCO
frequency is 2460MHz.
AK1546 setting :
R (Reference counter)=10000000/200000 = 50 (<Address0>:{R[13:0]}= “50”)
P=32 (<Address2>:{PRE[1:0]}=”10Bin”)
B=384 (<Address1>:{B[12:0]}=”384”)
A=12 (<Address1>:{A[5:0]}=”12”)
Frequency setting = 200kHz × [ (32×384) + 12] = 2460MHz
Lower limit for setting consecutive dividing numbers
In the AK1546, it is impossible to set consecutive dividing numbers below the lower limit. The lower limit is
calculated by the following formula;
N_min=P²-P
For example, in the case of P=16, it can be set 240 and over as consecutive dividing numbers.
MS1388-E-00
11
2012/3