la3335m Sanyo Semiconductor Corporation, la3335m Datasheet - Page 4

• Manufacturer Part Number: la3335m
• Description: Pll Fm Multiplex Demodulator For 3 V Headphone Stereos And Radio-cassette Recorders
• Manufacturer: Sanyo Semiconductor Corporation

3.
b)
Separation setting mothod
The LA3335M is so designed that the sub-signal gain is approximately 1.25 times as high as the main signal gain. The
separation can be set by attenuating the sub-signal of the FM detection output. (See Figure 3)
The value of capacitor Co depends on the attenuation of the sub-signal of the FM detection output and the IF IC output
impedance Ro. Fig. 4 shows the value of separation setting capacitor Co when Ro is set to 3 k .
For example, when the attenuation of sub-signal of the IF IC output is 0.9 time that of the main signal, it is seen from
Figure 4 that the value of Co is approximately 500 pF.
Connect the connection point of the semifixed resistor connected to pin 4 and the fixed resistor to a frequency counter
through the R
X
of 240 k . Fig. 2 shows how the error changes as the R
Ro 6 Output impedance
Input sub-signal attenuation, m – dB
Co – Attenuation
LA3335M
Figure 2
Figure 3
Figure 4
F – R
R
X
–
X
Vs = Sub-signal peak value
Vm = main signal peak value
Separation : 35 to 40 dB,
set to double hump response.
X
value is decreased.
No.2619-4/6