3/11
TDA7266SA
APPLICATION SUGGESTION
STAND-BY AND MUTE FUNCTIONS
(A) Microprocessor Application
In order to avoid annoying "Pop-Noise" during Turn-On/Off transients, it is necessary to guarantee the right St-
by and mute signals sequence. It is quite simple to obtain this function using a micropr ocessor (Fig. 1 and 2).
At first St-by signal (from
µ
P) goes high and the voltage across the St-by terminal (Pin 7) starts to increase ex-
ponentially. The external RC network is intended to turn-on slowly the biasing circuits of the amplifier, this to
avoid "POP" and "CLICK " on the outputs.
When this voltage reaches the St-by threshold level, the amplifier is switched-on and the external capacitors in
series to the input terminals (C3, C53) start to charge.
It's necessary to mantain the mute signal low until the capacitors are fully charged, this to avoid that the device
goes in play mode causing a loud "Pop Noise" on the speakers.
A delay of 100-200ms between St-by and mute signals is suitable for a proper operation.
Figure 1. Micropr ocess or Applicati on
RiInput Resis tance 25 30 KΩ
VTMUTE Mute Threshold for VCC > 6.4V; Vo = -30dB 2.3 2.9 4.1 V
for VCC < 6.4V; Vo = -30dB VCC/2
-1 VCC/2
-075 VCC/2
-0.5 V
VTST-BY St-by Threshold 0.8 1.3 1.8 V
IST-BY St-by Current V6 = GND 100 µA
eNTotal Output Voltage A Curve; f = 20Hzto 20KHz 150 µV
ELECTRICAL CHARACTERISTCS
(continued)
(V
CC
= 11V, R
L
= 8
Ω
, f = 1KHz, T
amb
= 25°C unless otherwise specified)
Symbol Parameter Test Condition Min. Typ. Max. Unit
1
2
4
Vref
ST-BY 7
IN1
C1 0.22µF
VCC
133
D95AU258A
+
-
-
+
OUT1+
OUT1-
15
14
12
MUTE 6
IN2
C3 0.22µF
+
-
-
+
OUT2+
OUT2-
8
9
S-GND
PW-GND
C5
470µFC6
100nF
R1 10K
C2
10µF
µP
R2 10K
C4
1µF