CMX972 Datasheet, PDF (10/41 Pages) CML Microcircuits – Small 32-lead VQFN Package

Quadrature Demodulator with IF PLL/VCO
CMX972
VCOP1 should be connected to VCOP2 and similarly VCON1 to VCON2 in order to form the negative
resistance loop. It is recommended that the parallel LC tank (L1/C1) is situated as close to the package as
possible, with the inductor closest to the device pins. Also the shorting of VCOP1 to VCOP2 and of
VCON1 to VCON2 occurs as close as possible to the tank circuit – this minimises the effects of series
inductance on the oscillator behaviour.
For further information see also section 7.7.
VCO
Negative
Resistance
(NR)
Amplifier
Enable
Enable
VCO
Output Buffer
Amplifier
L1 should have
a Q>30
L1
C1
C2
C3
CV1
CV2
R1 R2
Input from
Loop Filter
Figure 5 Example External Components – VCO External Tank Circuit
 2015 CML Microsystems Plc
10
D/972/2