CXA1538N SONY [Sony Corporation], CXA1538N Datasheet - Page 12

• Manufacturer Part Number: CXA1538N
• Description: FM STEREO/AM RADIO
• Manufacturer: SONY [Sony Corporation]

5. FM discriminator
6. FM muting circuit
7. Notes on patterns
For FM detection, the quadrature detection system is adopted. As a phase shifter, a ceramic resonator (CF
3 discriminator) applies to achieve adjustment-free detection. Though the sensitivity and selectability will be
slightly affected, the discriminator can be replaced by a coil as shown below. Combining CF2 (FMIF) and
CF3 (PM discriminator) poses problems with the distortion factor when deviation with the IF band central
frequency fo occurs. To this effect, use pairs of the same rank as indicated in the chart.
This IC has a built-in soft muting circuit.
As shown in the following I/O characteristics diagram, 23 dB (Typ.) muting is applied and noise level
reduced during weak electric field and out of tune instances.
1) Positions of FM ANT and OSC coils
2) Tuning circuit
3) Grounding pins
4) Ground bypass capacitors C5 (0.001 µF) and C6 (10 µF) connected to pin 21 as close as possible to pin
Locate those at right angles to each others to avoid inductance M through coupling. Further, insert a pin
21 pattern between patterns of pins 22, 20 and coils.
As the capacitances C1 to C4, L2 and L3 are the constants on the standard circuit board, check the
constants when a new circuit board is used.
Pin 17 is a grounding pin for AM, FM and FE ; pin 11 for IF ; and pin 30 for MPX. Use as thick as
possible a pattern since the grounding between ANT IN, BPF and pin 17 significantly stability, NF and
characteristics affects.
17.
A Red
B Blue
C Orange
D Black
E White
f
O
of CF2 and CF3
–23
10.70 MHz
10.67 MHz
10.73 MHz
10.64 MHz
10.76 MHz
3
18
INPUT LEVEL (dBµ)
IC with built-in soft MUTE
Conventional IC
BPF
17
S+N
N
16
ANT
IN
—12—
26
22pF
DISCRI
COIL
CXA1538M/N/S