CMX972 Datasheet, PDF (11/41 Pages) CML Microcircuits – Small 32-lead VQFN Package

Quadrature Demodulator with IF PLL/VCO
CMX972
L1 51nH (Note 1)
C1 8.2pF (Note 2)
C2 27pF
C3 27pF
CV1 SMV1705-079LF
CV2 SMV1705-079LF
R1 10kΩ
R2 10kΩ
Note 1: Tolerance of 2% or better recommended
Note 2: Tolerance of 5% or better recommended
Table 4 Internal VCO Amplifier Tank Circuit for 180MHz Operation
Alternative diodes may be used for CV1,CV2, for example the Toshiba 1SV305 (for which no other value
changes should be necessary). For increased tuning range the Skyworks SMV1249-079LF can be used: in
this case changing the tank circuit values is recommended. For operation at 180MHz, make L1 = 56nH
and C1=6.8pF, then C2 and C3 can be adjusted to give the desired tuning range: with C2, C3 = 27pF the
VCO gain (K_v) = 15 MHz/V and with C2, C3 = 12pF, K_v = 8MHz/V. For C2,C3 = 12pF, the value of C1
should be changed to 8.2pF, to give a control voltage closer to the centre of the tuning range.
DO
Output to
R2
Tank Cct
R1
C1
C3
C2
Figure 6 Example External Components – PLL Loop Filter
C1 150nF
C2 1µF
C3 15nF
R1 1.5kΩ
R2 2.4kΩ
Table 5 3^rd Order Loop Filter Circuit for 180MHz Operation
 2015 CML Microsystems Plc
11
D/972/2