AK1590 Datasheet, PDF (32/36 Pages) Asahi Kasei Microsystems – 1GHz Delta-Sigma Fractional-N Frequency Synthesizer

[AK1590]
14. Typical Evaluation Board Schematic
AK1590
100pF
REFIN
CP
220nF
VREF
Loop Filter
R3
C1 _R2'
R2
C3
SWIN
CPZ
BIAS
27k
RFINP
RFINN
C2
100pF
51
100pF
RFOUT
100pF
18
VCO
18
18
Fig. 13 Typical Evaluation Board Schematic
The input voltage from [CPZ] pin is used in the internal circuit. [CPZ] pin must not be open even when the Fast Lockup
feature is unused. For the output destination from [CPZ] pin, see “Fig.5 Loop Filter Schematic”. [SWIN] pin could be open
when the Fast 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. The on-resistance value of the internal switch is
150Ω for reference.
It is recommended to connect the exposed pad (the center of the back of the package) to ground, although it will not make
any impact on the electrical characteristics even if the pad is open. Moreover, all test pins should be connected to ground.
MS1478-E-01
32
2013/2