ICs for Audio Common Use
s
Technical Information (continued)
2.Application Note
1) Voltage gain
The voltage gain of the AN5273 can be varied by changing the resistor R2 as shown below :
Pin7,12
Pin8
11
AN5273
G
VI
G
V
input= 4 dB
which is fixed in
internal circuit.
R1 is always fixed at 20 kΩ.
R2 is variable.
G
VO
=
20 log (R
1
/R
2
)
R1
C
NF
=
10
µF
R2
Typical values are : R
1
=
20 kΩ, R
2
=
1 kΩ
G
VO
=
20 log (20 k/1 k)
=
26 dB
G
VTOTAL
=
G
VI
+
G
VO
=
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 :
AN5273
Microcomputer IC
R4
18 kΩ
C4
2.2
µF
R5
12 kΩ
PWM
output
Volume
attenuation
300
Ω
3
Volume
control
Fig. Volume control interface circuit for AN5273
5 (V)
Volume at Pin3
Fig. Volume characteristic of AN5273
0
0.6
3) Mute control
Mute is ON when 5 V is applied to Pin1. Then Q1 would turn ON and able to drive other part of the circuits. The
external RC components provide a time constant for switching ON and OFF.
Mute ON 5 V
0V
OFF
Z
MUTE
C
1.0
µF
The purpose of the Mute is to
attenuate the AC signal before
it goes to the output.
R
100 kΩ
1
20 kΩ
Q1
0V
Threshold voltage at Pin1 :
Mute OFF
1.8 V 2.1 V
Mute ON
5V
5
PANASONIC [ PANASONIC SEMICONDUCTOR ]
