AK1544 Datasheet, PDF (12/37 Pages) Asahi Kasei Microsystems – 1300MHz Integer-N Frequency Synthesizer

[AK1544]
2. Charge Pump and Loop Filter
In the AK1544, the fast lockup could be achieved by changing a charge pump current and enabling the loop filter. This is
called Fast Lockup mode. For details, see ”3. Fast Lockup Mode” on page 14.
The loop filter is external and connected to [CP], [SWIN] and [CPZ] pins. The [CPZ] pin should be connected to the R2
and C2 , which are intermediate nodes, even if the Fast Lockup is not used. Therefore, R2 must be connected to the [CP]
pin, while C2 must be connected to the ground.
Phase Detector
up
down
Timer
Loop Filter
CP
R3
C1 _R2'
R2
C3
VCO
SWIN
C2
CPZ
Fig. 5 Loop Filter Schematic
MS1350-E-01
12
2013/03