Pair Gain Dual SPM Detector
CMX661
1.4
External Components
Figure 2 Typical External Components
R1
R2
R3
R4
R5
R6
120kΩ
120kΩ
100kΩ
100kΩ
120kΩ
120kΩ
±1%
±1%
±1%
±1%
±1%
±1%
R7
R8
R9
R10
X1
100kΩ
100kΩ
15kΩ
15kΩ
3.579545MHz
±1%
±1%
±1%
±1%
C1
C2
C3
C4
C5
C6
1.0µF
1.0µF
330pF
330pF
330pF
330pF
±20%
±20%
±5%
±5%
±5%
±5%
Input amplifier components R1, C3, R2, C4, R5, C5, R6 and C6 should be chosen to set the required
sensitivity of the CMX661 (see section 1.6.4). Typical values only are shown above. Note that when
calculating/selecting gain components, R3, R4, R7 and R8 should always be greater than or equal to
100kΩ. V
BIAS
is not available from the CMX661 and so must be generated by an external voltage divider
(R9 and R10) from V
DD
. Particular attention should be paid to decoupling V
DD
and keeping the power,
ground and signal lines free from unnecessary noise.
Telephone systems may have unusually high dc and ac voltages present on the line, as either differential
or common mode signals. If the CMX661 is part of a host system which does not have its own input
protection, then protection diodes must be added to both signal inputs (+ and ) so that the voltage on
any pin is limited to within V
SS
0.3V and V
DD
+ 0.3V. The breakdown voltage of capacitors and the
peak inverse voltage of diodes must be sufficient to withstand the sum of the dc and peak-peak ac
voltages applied.
©
2002 CML Microsystems Plc
6
D/661/3
CMLMICRO [ CML MICROCIRCUITS ]
