SILAN SC7422S

SC7422
2-CH AUDIO POWER AMPLIFIER
2W x 2
DESCRIPTION
The SC7422 is a class AB power amplifier which designed for dual
audio purpose. It can deliver 2W × 2 power output to the 4
load in the
SOP-16-375-1.27
5V operation voltage. Total harmonic distortion is lower than 0.03%. The
output mode can be switched between the SE and BTL mode. The
volume also can be changed by a 32 steps volume controller. Moreover,
the SC7422 requires a few extra components in the application. It is
suitable for small or portable products.
FEATURES
DIP-16-300-2.54
* Operation voltage : 5V
* Output power : 2W×2(RL=4 )
* Low harmonics distortion (THD=0.03%)
* 32 steps volume control with 1.5dB per step from -45dB to 0dB
* Two output modes (SE and BTL) switched
* Low quiescent operation current
* No POPO noise when turn on/off
ORDERING INFORMATION
Device
Package
SC7422
DIP-16-300-2.54
SC7422S
SOP-16-375-1.27
* Standby function, Low standby current(Is<0.7 A)
* Thermally protected
APPLICATIONS
* LCD Monitors for TV
* Portable audio
* Multimedia audio
* Other audio applications
BLOCK DIAGRAM
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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Page 1 of 8
SC7422
ABSOLUTE MAXIMUM RATING
Characteristics
Symbol
Rating
Unit
VCC
0 ~7
V
Vin(max)
-0.3 ~ VCC +0.3
V
Iin(max)
-10 ~+10
mA
Operating Ambient Temperature
Tamb
-40 ~+85
°C
Storage Temperature
Tstg
-65 ~+150
°C
JA
88.8 (**)
°C/W
JC
26 (**)
°C/W
Supply Voltage
Maximum Input Voltage For Any Pin
Maximum Input Current For Each Input
Pin (*)
Thermal
Resistance
From
Junction
To
Ambient
Thermal Resistance From Junction To Case
(*) Maximum instantaneous input current for any pin must be less than 100mA, so that the CMOS latch-up effect
can be avoided.
(**) Ambient Temperature: Tamb=25°C.
ELECTRICAL CHARACTERISTICS
(Refer to the test circuit, VCC=5V; f=22Hz~22KHz; Tamb=25°C, unless otherwise specified.)
Characteristics
Supply Voltage
Quiescent Operation Current
Symbol
Test conditions
VCC
Is
V
BTL
8
10
14
mA
SE
6
8
12
mA
0.2
0.7
1
µA
THD=1%, RL=8Ω
1.0
1.1
1.1
THD=10%, RL=8Ω
1.2
1.4
1.6
THD=1%, RL=4Ω
1.4
1.6
1.8
THD=10%, RL=4Ω
1.8
2.0
2.1
THD=1%, RL=32Ω
80
85
90
THD=10%, RL=32Ω
100
110
120
Po=0.2W, RL=4Ω
0.03
0.05
0.07
%
Po=1W, RL=4Ω
0.06
0.08
0.15
%
Po=50mW, RL=32Ω
0.03
0.05
0.07
%
DC Vol = 5V, F = 1kHz
-1
0
+1
DC Vol = 17%Vcc
-44
-45
-46
Po
Volume Control Range
THD
BTL
SE
Vatt
Unit
6
SE
Distortion
Max.
5
BTL
Total Harmonic
Typ.
3
Shutdown = ON
Output Power
Min.
W
mW
dB
Volume Control Step
Vstep
Vatt = 0 ~ -45dB
1.3
1.5
1.7
dB
Mute
Mute
DC Vol = 0V
-85
-88
-90
dB
Rin = Rf = 20kΩ
-1
0
+1
dB
BTL
85
88
91
77
80
83
Channel Balance
CB
Channel Separate
CS
SE
F=1kHz
dB
Signal-to-Noise Ratio
SNR
85
90
91
dB
Output Noise Voltage
Vno
25
40
50
µV
(To be continued)
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Page 2 of 8
SC7422
(Continued)
Characteristics
Symbol
Output Offset Voltage
Supply
Voltage
Voff
Ripple
SVRR
Rejection
Thermally protected
TH
Input Voltage For Shutdown
VSD
Pin
Input Voltage For
VSB
SE/BTL Pin
Test conditions
Min.
Typ.
Max.
Unit
25
50
100
mV
DC Vol = 0V
From +OUT to -OUT
BTL
58
60
63
52
55
58
Overheat to shutdown
-
120
-
Return to normal operation
-
80
-
20%
30%
SE
Shutdown = OFF
Shutdown = ON
BTL
SE
F=1kHz
Vcc=3~5V
Vcc=3~5V
50%
°C
60%
10%
80%
dB
20%
90%
Vcc
Vcc
PIN CONFIGURATION
PIN DESCRIPTION
Pin No.
Pin Name
I/O
Pin Description
1
Shutdown
I
Stand-by control, logic high active
2
VCC
--
Supply
3
DC Vol
I
Volume control
4
VO1
I
Buffer output of channel 1
5
VIN1
I
Signal input of channel 1
6
VIN2
I
Signal input of channel 2
7
VO2
I
Buffer output of channel 2
8
GND
--
Ground
9
+OUT2
O
Non inverted loudspeaker output of channel 2
10
VCC
--
Supply
11
-OUT2
O
Inverted loudspeaker output of channel 2
12
SE/BTL
I
Output mode control. When this pin is logic high, SE mode is selected.
When it is logic low, BTL mode is selected.
(To be continued)
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SC7422
(Continued)
Pin No.
Pin Name
I/O
Pin Description
13
Bypass
O
Half supply voltage ripple rejection
14
-OUT1
O
Inverted loudspeaker output of channel 1
15
VCC
--
Supply
16
+OUT1
O
Non inverted loudspeaker output of channel 1
FUNCTION DESCRIPTION
Gain Setting for Input Stage
The gain for each audio input stage of the SC7422 is set by external resistors R1 and R2 (see typical
application circuit). It is recommended that R1 = R2 = 20kΩ in the application and the gain is 0dB.
If the amplitude of audio input voltage is lower, for example, the peak-peak value is less than 2Vpp, it should be
improve the gain, whereas, it should be reduce the gain. However, the amplitude of audio input voltage is so high
that the output wave would be distortion. Therefore, the amplitude of audio signal source should be checked at
first. And the gain in the application should be set following Table 1.
Table 1 Gain Setting for Input Stage
Operation
Voltage
VCC=3V
The peak-
Gain Setting
peak value of
for Input
input voltage
Stage
VIN <1.25Vpp
+6dB
VIN <2.5Vpp
0dB
VIN <5Vpp
-6dB
Operation
Voltage
VCC=5V
The peak-
Gain Setting
peak value of
for
input voltage
Input Stage
VIN <2Vpp
+6dB
VIN <4Vpp
0dB
VIN <8Vpp
-6dB
Otherwise, the minimum value of input resistor R1 is 10kΩ, in order to ensure proper impedance for input.
32 Steps Volume Control
The SC7422 includes a 32 steps volume controller. It changes the volume gain linearly with 1.5dB per step from
-45dB to 0dB. The volume is controlled by input voltage of DC Vol pin. As the voltage was increasing, the volume
is louder. Table 2 shows the relationship of them.
Table 2 32 Steps Volume Setting
Step
Volume
DC Vol
DC Vol
(dB)
VH(%)
VL(%)
Step
Volume
DC Vol
DC Vol
(dB)
VH(%)
VL(%)
64.2
17
-24
38.1
30.4
64.4
62.8
18
-25.5
35.6
29.0
-3
63.0
61.2
19
-27
31.8
27.4
4
-4.5
61.4
59.4
20
-28.5
29.2
25.4
5
-6
59.8
57.6
21
-30
27.6
23.8
1
0
Vcc
2
-1.5
3
(To be continued)
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Page 4 of 8
SC7422
(Continued)
Volume
DC Vol
DC Vol
Volume
DC Vol
DC Vol
(dB)
VH(%)
VL(%)
(dB)
VH(%)
VL(%)
6
-7.5
57.9
56.0
22
31.5
26.2
21.8
7
-9
56.1
54.0
23
-33
24.0
20.0
8
-10.5
54.1
51.8
24
-34.5
22.5
18.0
9
-12
52.1
48.8
25
-36
20.4
14.4
10
-13.5
49.4
47.4
26
-37.5
18.0
13.0
11
-15
47.5
45.4
27
-39
15.1
11.0
12
-16.5
45.5
43.6
28
-40.5
13.1
9.0
13
-18
44.0
41.6
29
-42
10.6
7.2
14
-19.5
41.8
39.8
30
-43.5
8.8
5.4
15
-21
39.8
37.6
31
-45
6.7
3.0
16
-22.5
38.3
36.6
32
MUTE
4.3
GND
Step
Step
Output Mode Control
The output mode of the SC7422 can be switched between the SE (Single-Ended) and BTL (Bridge-Tied Load)
mode. It is recommended to apply BTL mode to obtain more output power while driving the loud speaker. SE
mode can be set to shutdown some parts of amplifiers while driving the stereo headphone. Therefore, the
quiescent operation current is reduced.
POPO Noise Suppress
When an audio power amplifier with a single supply turns on, the POPO Noise can be heard. The reason is that
the output voltage of amplifier would take hundreds of milliseconds to increase from 0V to 1/2 Vcc.
This time is controlled by CB, the external capacitor of Bypass pin. As the CB was increasing, the time is longer,
so it is much better to suppress POPO noise. However, the charging and discharging time for the input or output
capacitors should be less than this time. Therefore, CB is related with the input or output capacitors. The values
of these capacitors are recommended in the typical application circuit.
Thermally protected
There is a thermally protected protection circuit in the SC7422. If the chip temperature is over 120°C, the
protection circuit will start up to shutdown the output stages of audio power amplifier. The chip will return to the
normal operation, until the chip temperature falls to 80°C.
Power Dissipation and Heat Sinking
When the load is a resistor, the maximum of average power dissipation for the SC7422 is calculated as follows:
PDISS(MAX) = 2(2Vcc)2 / (2π2RL) + PQ
Where Vcc is the operation voltage, RL is the load resistor, PQ is the static power consumption.
PQ=VCC×Is
Where Is is the operation current. For example, if the SC7422 drives the 4
load in 5V supply, the power
dissipation is 2.6W.
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SC7422
There is the formula of heat sinking for the SC7422:
JA =
Where
JA
(TJ(max) -TA )/ PDISS
is the thermal resistance from junction to ambient, TJ(max) is the junction temperature, TA is ambient
temperature, PDISS is the power dissipation.
If the junction temperature remains below 150°C but the ambient temperature has reached to 50°C, the total
junction-to-ambient thermal resistance must be less than
JA =
JA
calculated as follows:
(150°C - 50°C) / 2.6W =38.4°C/W.
Using JC=26°C /W, the heat-sink thermal resistance must be less than:
JA
-
JC
= 12.4°C/W
So the SC7422 doesn’
t need heat sink in the normal operation. In application, the copper foil which connects
GND on PCB can be utilized for heat sinking to maintain proper operation temperature.
TYPICAL APPLICATION CIRCUIT
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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SC7422
PACKAGE OUTLINE
Unit: mm
SOP-16-375-1.27
Unit: mm
0.20±0.10
2.50±0.20
0.70±0.10
7.50±0.20
10.30±0.20
DIP-16-300-2.54
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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REV:1.0
2006.11.13
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SC7422
HANDLING MOS DEVICES:
Electrostatic charges can exist in many things. All of our MOS devices are internally protected against
electrostatic discharge but they can be damaged if the following precautions are not taken:
• Persons at a work bench should be earthed via a wrist strap.
• Equipment cases should be earthed.
• All tools used during assembly, including soldering tools and solder baths, must be earthed.
• MOS devices should be packed for dispatch in antistatic/conductive containers.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
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2006.11.13
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