BA1442A データシートの表示（PDF） - ROHM Semiconductor

部品番号

コンポーネント説明

メーカー

BA1442A

AM radio / FM IF stereo system IC

ROHM Semiconductor 

Audio ICs

BA1442A

FSelecting of attached components and operation notes

Pin 1: FM ceramic filter (CF1)

The input impedance of pin 1 is 330Ω, so it should be con-

nected to a ceramic filter that has an output impedance

of 330Ω. Connect the earth point of the ceramic filter to

the input side GND. In addition, the connection distance

between the ceramic filter and pin 1 should be as short

as possible.

Pin 2: FM IF bypass

This pin is used to ensure stable FM, and it is normally

connected to pin 19 (Vreg). If it is not possible to achieve

stable FM, ground pin 2 via a 0.01µF capacitor. The earth

point in this case will be on the GND side of the FM ce-

ramic filter.

Pin 3: Power supply bypass capacitors (C7 and C8)

C7 should be a capacitor with good high-frequency char-

acteristics. Connect it between the base of the legs of pin

3 (VCC) and pin 5 (GND). The purpose of C8 is ripple rejec-

tiun, and it can be connected a little further away.

Pin 4: FM quadrature detector phase-shift coil (T3)

Pin 3 and 4 are connected internally by a 3.3kΩ damping

resistor. The earth point for the phase-shift coil should be

VCC, so ensure that it is at the same voltage as pin 3 (VCC).

Pin 6: FM detector low-pass filter capacitor (C11)

This capacitor smooths the 2 10.7MHz (21.4MHz) sig-

nal generated by FM quadrature detection, and prevents

leakage of the 10.7MHz signal. The output impedance of

pin 6 (5kΩ) and C11 form a low-pass filter. Connect the

earth point to a GND other than the input side GND. If you

do not do this, the input carrier will return from the output,

and may result in poor stability.

If the capacitor is too large, poor separation will result.

Pin 7: FM detector output coupling capacitor (C9)

FM detector output is input to the MPX throngh C9. The

input impedance of pin 7 (100kΩ) and C9 form a high-

pass filter. If the value of C9 is too low, poor bass region

separation will result.

Pin 8: AM detector output coupling capacitor (C10)

AM detector output is input to the MPX through C10. The

input impedance of pin 8 (20kΩ) and C10 form a high-pass

filter and improves the AM fidelity. Characteristic curves

for different values of C10 are given in the graph in Fig. 3.

Pin 9: AM high-cut capacitor (C12)

The input impedance of pin 9 (8kΩ) and C12 form a low-

pass filter. To prevent beat from occurring between carri-

er leak from the detector output pin and the input signal,

connect a capacitor of about 1000pF, even if not using

high-cut. Connect the earth point to a GND other than the

input side GND. Characteristic curves for different values

of C12 are given in the graph in Fig. 4.

346

Share Link: