AK1573 Datasheet, PDF (30/42 Pages) Asahi Kasei Microsystems – Low Noise Integrated VCO

[AK1573/AK1573B/AK1573C]
13.2. Frequency Setting
The following formula is used to calculate the frequency setting for the AK1573.
Frequency Setting ＝ F_PFD × ( P × B + A)
F_PFD
: PFD frequency
P
: Prescalor value (refer to Address0x02 : Pre[1:0] )
B
: B (Programmable) counter (refer to Address0x01 : B[12:0] )
A
: A (Swallow)counter (refer to Address0x01 : A[5:0] )
○ Example
Set the AK1573 as follows to obtain Frequency setting =2100MHz with F_PFD = 200kHz
P = 8 ( Address0x02 : Pre[1:0] bits = 0 )
B = 1312 ( Address0x01 : B[12:0] bits = 1312 )
A = 4 ( Address0x01 : A[5:0] bits = 4 )
Frequency setting = 200k × (8 × 1312 + 4) = 2100MHz
Note) Lower limit for setting consecutive dividing numbers
For the AK1573, it is not possible to set consecutive dividing ratio below the lower limit
(The lower limit is determined by a dividing ratio set for the prescaler).
The following table shows an example where consecutive dividing numbers below the lower limit cannot
be set. The consecutive dividing ratio can be set when B ≥ P-1.
*P=8 (Dual modulus prescaler 8/9)
P B[12:0] A[5:0]
8
6
6
8
7
0
8
7
1
:
:
:
8
7
7
8
8
0
:
:
:
Dividing ratio
54
55 cannot be set as an N divider.
This is the lower limit.
56
56 or over can consecutively be set as
an N divider.
57
:
63
64
:
015009351-E-00
- 30 -
2015/8