CMX972 Datasheet, PDF (8/41 Pages) CML Microcircuits – Small 32-lead VQFN Package

Quadrature Demodulator with IF PLL/VCO
4 External Components
CMX972
4.1 Power Supply Decoupling
This device has separate supply pins for the analogue and digital circuitry; a 3.3V nominal supply is
recommended.
V_SUPPLY
Ground
R3
R2
R1
C1
C2
C3
V_CCSYNTH
V_CC
V_DD
Figure 2 Power Supply Connections and Decoupling
V_RFGND
V_SS
C1 10nF
C2 10nF
C3 10nF
R1 10
R2 3.3
R3 10
Resistors 1%, capacitors 20%
Table 2 Power Supply Component Values
Note:
It is expected that low-frequency interference on the 3.3V supply will be removed by active regulation. A
large capacitor is an alternative but may require more board space and so may not be preferred. The
supply decoupling shown is intended for RF noise suppression. It is necessary to have a small series
impedance prior to the decoupling capacitor for the decoupling to work well. This may be achieved cost
effectively by using the resistor as shown. The use of resistors results in small dc voltage drops. Choosing
resistor values approximately inversely proportional to the dc current requirements of each supply pin
ensures the dc voltage drop on each supply is reasonably matched. In any case, the dc voltage change
that results are well within the design tolerance of the device. If higher impedance resistors are used then
greater care will be needed to ensure that the supply voltages are maintained within tolerance, including
when parts of the device are enabled or disabled.
 2015 CML Microsystems Plc
8
D/972/2