AK1542A Datasheet, PDF (12/37 Pages) Asahi Kasei Microsystems – 20 to 600MHz Integer-N Frequency Synthesizer

[AK1542A]
2. Charge Pump and Loop Filter
In AK1542A, the fast Lock Up could be achieved by changing a charge pump current and enabling the loop filter. This is
called Fast Lock Up mode. For details, see ”3. Fast Lock Up Mode” on page 13.
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 Lock Up 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
MS1399-E-00
- 12 -
2012/3