CXA1742Q
1) Power supply
Power supply pins (Pins 11, 24, and 33) must be decoupled with the shortest distance.
2) Oscillator
The figures below show how to use the CXA1742Q oscillator.
VCC
VCC
SG
102
C2
20
20
L
19
Crystal
L
VCC
19
C
C1
VCC
(a) Inputting a local oscillation signal from an external (b) Configuring a Colpitts-type oscillator circuit.
circuit.
The C1, C2, and L must be changed according to
the crystal characteristics.
The circuit current varies with the externally fed
signal amplitude.
The oscillation Tr in the IC is internally subjected to
AGC so that the oscillation level at Pin 19 is not
likely to be affected by temperature or supply
voltage fluctuations.
The reason is that the AGC circuit, which works to
maintain the oscillation amplitude constant when a
Colpitts-type oscillator circuit is formed, also
operates when an external local oscillation signal
is input. Tune the L and C to the Pin 20 input
signal frequency or the needed frequency.
The tuning point is decided at the minimum of the
Pin 19 current.
Do not decide the point when the probe is
connected to Pin 19 because the tuned frequency
is deviated by the stray capacitor of the probe.
3) Mixers
Since the BPF in the IC has an fo value as low as 60 kHz, the IC employs an image rejection type of mixer
having an enhanced interference elimination capability. Therefore, the two internal mixers must be
accurately adjusted so that their gains are equal. Normally, an adequate degree of image rejection is
provided without using Pins 28 and 29. However, when they are used for adjustment purposes, an
increased degree of image rejection will result.
500Ω
29
28
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SONY [ SONY CORPORATION ]
