AN5272 Просмотр технического описания (PDF) - Panasonic Corporation

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производитель

AN5272

4.0 W ×2 (18 V, 8 Ohm) Power Amplifier with Variable Audio Output and Volume Control

Panasonic Corporation 

ICs for Audio Common Use

AN5272

s Technical Information (continued)

2.Application Note

1) Voltage gain

The voltage gain of the AN5272 can be varied by changing the resistor R2 as shown below :

GVI

GV input = 4 dB Pin8

which is fixed in 11

internal circuit.

Pin7,12

R1

R1 is always fixed at 20 kΩ.

R2 is variable.

GVO = 20 log (R1/R2)

Typical values are : R1 = 20 kΩ, R2 = 1 kΩ

CNF = 10 µF

R2

GVO = 20 log (20 k/1 k)

= 26 dB

GVTOTAL = GVI + GVO

= 4 dB + 26 dB

= 30 dB

2) DC volume control

The DC volume control range is 0 V to 5 V. This range is used in order to be easily controlled by micro-computer

using PWM output. The recommended circuit and volume attenuation characteristic are shown below :

AN5272

300 Ω 3

Volume

control

R4

18 kΩ

C4

2.2 µF

R5

12 kΩ

Microcomputer IC

PWM

output

Volume

attenuation

Fig. Volume control interface circuit for AN5272

0 0.6 Volume at Pin3 5 (V)

Fig. Volume characteristic of AN5272

3) Oscillation

To prevent oscillation, it is advisable to use RC (Zobel network) at output. C of polyester film capacitor has smaller

characteristic fluctuation with temperature and frequency. The resistor R connected in series with C is effective for

phase correction at high frequency, and as a result, it improves the oscillation allowance.

1000 µF

Pin7

12

C 0.047 µF

R 20 Ω

RL = 8 Ω

5

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