AK1547 Datasheet, PDF (11/37 Pages) Asahi Kasei Microsystems – 4GHz Low Noise Integer-N Frequency Synthesizer

[AK1547]
8. Block Functional Descriptions
1. Frequency Setup
The following formula is used to calculate the frequency setting for the AK1547.
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.
AK1547 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 AK1547, it is impossible to set consecutive dividing numbers below the lower limit. The lower limit, N_min,
depends on the Prescaler setting, and can be calculated by the following formula;
N_min=P²-P
The dividing number below N_min can’t be set for succession. For example, in the case of P=16, 240 and over
can be set as consecutive dividing number.
MS1464-E-00
11
2012/9