AK1541_17 Datasheet, PDF (32/37 Pages) Asahi Kasei Microsystems – 20 to 600Mhz Delta-Sigma Fractional-N Frequency Synthesizer

[AK1541]
14. Typical Evaluation Board Schematic
AK1541
100pF
REFIN
CP
220nF
VREF1
Loop Filter
R3
C1 _R2'
R2
C3
220nF
VREF2 _SWIN
CPZ
BIAS
27kΩ
RFINP
RFINN
C2
100pF
100pF
51Ω
RFOUT
100pF
VCO
18Ω
18Ω
18Ω
Fig. 14 Typical Evaluation Board Schematic
The input voltage from the [CPZ] pin is used in the internal circuit. The [CPZ] pin must not be open even when the fast
lockup feature is unused. For the output destination from the [CPZ] pin, see “P.12 Fig.5 Loop Filter Schematic”. The
[SWIN] pin could be open even when the first lockup feature is not used.
R2 and R2’ are connected in parallel with internal switch in Fast Lockup. These R2 and R2’ parallel resistance value is
required for calculating loop bandwidth and phase margin in Fast Lockup. An On resistance value of the internal switch is
150Ω for reference.
MS1043-E-05
32
2013/03