AK1548 Datasheet, PDF (11/42 Pages) Asahi Kasei Microsystems – 8GHz Low Noise Integer-N Frequency Synthesizer

[AK1548]
8. Block Functional Descriptions
1. Frequency Setup
The following formula is used to calculate the frequency setting for the AK1548.
Frequency setting (external VCO output frequency) = F_PFD x N
Where :
N
F_PFD
P
B
A
: Dividing number N = [ (P x 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 1MHz and VCO
frequency is 7400MHz.
AK1548 setting :
R (Reference counter)=10000000/1000000 = 10 (<Address0>:{R[13:0]}= “10”)
P=32 (<Address2>:{PRE[1:0]}=”10Bin”)
B=231 (<Address1>:{B[12:0]}=”231”)
A=8 (<Address1>:{A[5:0]}=”8”)
Frequency setting = 1M × [ (32×231) + 8] = 7400MHz
Lower limit for setting consecutive dividing numbers
In the AK1548, it is not possible to set consecutive dividing numbers below the lower limit.
(The lower limit is determined by a dividing number set for the prescaler.)
The following table shows an example where consecutive dividing numbers below the lower limit cannot be set.
The consecutive dividing numbers can be set when B ≥ P-1.
MS1364-E-00
11
2012/1