St-by Threshold0.81.31.8V
ST-BY current V6 = GND100µA
Total Output Noise VoltageA curve
APPLICATIONSUGGESTION
STAND-BYAND MUTE FUNCTIONS
(A) MicroprocessorApplication
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 microprocessor(Fig.1 and 2).
At first St-by signal (from mP) goes high and the
voltage across the St-by terminal (Pin 7) startsto
increase exponentially. The external RC network
is intended to turn-onslowly the biasing circuits of
(Continued)
150
f = 20Hz to 20kHz
the amplifier, this to avoid ”POP” and ”CLICK” on
the outputs.
When this voltage reaches the St-by threshold
level, the amplifier is switched-onand the external
capacitors in series to the input terminals (C3,
C5) start to charge.
It’s necessaryto 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 properoperation.
Figure 1: MicroprocessorApplication
V
µ
µP
IN1
ST-BY
MUTE
C1 0.22µF
R1 10K
C2
10µF
R2 10K
C4
1µF
S-GND
V
CC
4
7
9
Vref
68
+
-
-
+
133
1
OUT1+
2
OUT1-
PW-GND
C5
470µF
D98AU833A
C6
100nF
3/9
TDA7266M
Figure 2:
MicroprocessorDriving Signals.
+VS(V)
+18
V
IN
(mV)
V
ST-BY
pin 7
1.8
1.3
0.8
V
MUTE
pin 6
4.1
2.9
2.3
I
q
(mA)
V
OUT
(V)
OFF
ST-BY
MUTE
PLAYMUTEST-BY
(B) Low Cost Application
In low cost applications where the mP is not present, the suggestedcircuit is shown in fig.3.
The St-by and mute terminals are tied together
and they are connected to the supply line via an
OFF
D96AU259
externalvoltage divider.
The device is switched-on/off from the supply line
and the external capacitor C4 is intendedto delay
the St-by and mute threshold exceeding, avoiding
”Popping”problems.
4/9
TDA7266M
Figure 3a:
IN1
R1
47K
R2
47K
Stand-aloneLow-cost Application.
C3 0.22µF
IN1
ST-BY
C4
10µF
S-GND
MUTE
4
7
9
Vref
68
V
CC
133
+
1
470µF
OUT1+
C1
C2
100nF
-
-
2
OUT1-
+
PW-GND
Figure 3b:
DASHED PARTS
ARE NOT TO BE
CONSIDERED
D98AU834A
PCB and ComponentLayout of the Application Circuit (Fig. 1).
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences
of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is
granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are
subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products
are not authorized for use as criticalcomponents in lifesupport devices or systems without express written approval ofSTMicroelectronics.
The ST logo is a registeredtrademarkof STMicroelectronics
1998 STMicroelectronics– Printed in Italy – AllRights Reserved
STMicroelectronics GROUP OF COMPANIES
Australia - Brazil - Canada - China- France - Germany - Italy - Japan - Korea- Malaysia - Malta - Mexico - Morocco - The Netherlands -
Singapore - Spain - Sweden - Switzerland- Taiwan - Thailand- United Kingdom - U.S.A.
9/9
Loading...
+ hidden pages
You need points to download manuals.
1 point = 1 manual.
You can buy points or you can get point for every manual you upload.