SA7347
4-CH AUDIO POWER AMPLIFIER(8W X4)
DESCRIPTION
SA7347 is a four channel audio amplifier including two non
inverted amplifiers and two inverted amplifiers, so it can be
conveniently applied in Bridge-Tied Load (BTL) mode.
Built-in
protection
circuit
based
on
multiple
temperature
measurements inside SA7347 makes it possible for all supply
voltages and load conditions to export maximum power.
FEATURES
* Soft clip
* Standby and mute mode
* No on/off switching plops
* High supply voltage ripple rejection
* Thermally protected
* Outputs short circuit protected to ground, supply and across
the load
HSIP-15
ORDERING INFORMATION
Device
SA7347
Package
HSIP-15
APPLICATIONS
* Television, PC speakers and mini stereo system, etc
BLOCK DIAGRAM
HANGZHOU MICROELECTRONICS CO.,LTD
Http: www.silan.com.cn
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REV:1.1
2007.07.27
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SA7347
ABSOLUTE MAXIMUM RATING
(T
amb
=25°C)
Characteristics
Supply Voltage
Input Voltage
Repetitive Peak Output Current
Storage Temperature Range
Ambient Temperature Range
Total Power Dissipation
Symbol
V
CC
V
IN
I
ORM
T
stg
T
amb
P
tot
non-operating
Condition
Operating
Rating
-0.3 ~ +22
-0.3 ~ V
CC
+ 0.3
4
-55 ~ +150
-40 ~ +85
69
17
In free air
All channels driven
40
1.3
Unit
V
V
A
°C
°C
W
V
°C/W
°C/W
Supply Voltage to Guarantee Short-circuit Protection V
CC(SC)
Thermal Resistance From Junction to Ambient
Thermal Resistance From Junction to Case
R
th(j-a)
R
th(j-c)
ELECTRICAL CHARACTERISTICS
(Unless otherwise stated, V
CC
=15V, R
L(SE)
=4 , R
L(BTL)
=8 , f=1kHz, V
stby=
V
CC
, T
amb
=25°C)
Characteristics
Quiescent Supply Current
Standby Supply Current
DC Output Voltage
Differential Output Voltage Offset
Select Voltage on Pin STBY
Symbol
Icq
Istby
V
O
V
OUT
BTL(*)
play
Vstby
mute
standby
Select Current on Pin STBY
Ibias
V
CC
/2+2<Vstby< V
CC
THD=10%, BTL, RL=4
SE RL=3
THD=10%
Output power
P
O
SE RL=4
BTL RL=6
BTL RL=8
SE RL=3
THD=1%
SE RL=4
BTL RL=6
BTL RL=8
Total Harmonic Distortion
Voltage Gain
Input Impedance
Noise Output Voltage
THD
Gv
Zin
Vn(o)
P
O
=1W
SE
BTL
SE
BTL
SE
BTL
SE
BTL
R
L
=
Test condition
Min.
--
--
--
--
V
CC
/2+3
4.5
0
--
--
--
--
--
--
--
--
--
--
--
--
25
31
40
20
--
--
Typ.
100
--
6.9
--
--
--
--
--
22
8
6
17
13
7
5
14
10
0.1
0.05
26
32
60
30
150
200
Max.
145
1
--
170
V
CC
V
CC
/2+2
0.8
20
--
--
--
--
--
--
--
--
--
0.5
0.5
27
33
--
--
--
--
µV
%
dB
W
µA
V
Unit
mA
mA
V
mV
(To be continued)
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SA7347
(Continued)
Characteristics
Symbol
Test condition
frip=1kHz(**)
SE
BTL
BTL
SE
BTL
Rsource=0
SE
BTL
SE
BTL
Min.
--
--
--
--
--
--
50
50
--
--
Typ.
60
65
60
65
--
--
60
65
--
--
Max.
Unit
dB
dB
µV
dB
dB
Supply Voltage Ripple Rejection
SVRR
frip=100Hz~ SE
20kHz(**)
--
--
--
--
150
250
--
--
1
1
Output Voltage in Mute Mode
Channel Separation
Channel Balance
(*)
(**)
V
OUT
= | V
OUT
V
OUT
Vo(mute)
CS
CB
|
Supply voltage ripple rejection is measured at the output, with a source impedance Rsource = 0
at the
input and with a frequency range from 20 Hz to 22 KHz. The ripple voltage is a sine wave with a frequency fripple
and an amplitude of 300 mVrms, which is applied to the positive supply rail.
Pin configurations
Pin descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Pin Name
OUT1+
VCC1
OUT2-
IN2
SGND
IN1
IN3
GND
STBY
SVR
IN4
CIV
OUT3-
VCC2
OUT4+
Description
non inverted loudspeaker output of channel 1
supply voltage channels 1 and 2
inverted loudspeaker output of channel 2
input channel 2
signal ground
input channel 1
input channel 3
power ground
mode selection input: standby, mute and play
half supply voltage ripple rejection
input channel 4
common input voltage ripple rejection
inverted loudspeaker output of channel 3
supply voltage channels 1 and 2
non inverted loudspeaker output of channel 4
HANGZHOU MICROELECTRONICS CO.,LTD
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REV:1.1
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SA7347
FUNCTION DESCRIPTION
Input configuration
The formula of the input cut-off frequency is:
fi(cut
−
off)
=
1
2
π
(Ri
×
Ci )
and Cin = 220nF:
=
12Hz
)
For SE application Rin = 60k
fi(cut
−
off)
=
1
2
π
(60
×
10
3
×
220
×
10
9
For BTL application Rin = 30k and Cin = 470nF:
fi(cut
−
off)
=
1
2
π
(30
×
10
3
×
470
×
10
9
)
=
11Hz
Because of high input impedance, large capacitor values for the inputs are not necessary. The smaller input
capacitor values help to reduce the switch on delay during charging of the capacitors. This results in a good low
frequency response and good switch on behavior.
BTL application
Using the SA7347 as a BTL amplifier offers the following advantages:
Ø
Ø
Ø
Ø
Low peak value of the supply current
Ripple frequency on the supply voltage is twice the signal frequency
Good low frequency performance
No expensive DC-blocking capacitor
Mode selection
By changing properly DC voltage of pin STBY, SA7347 has follow functional modes which can be selected for
all channels.
Ø
Ø
Ø
0 < STBY < 0.8V: The current consumption is very low and the outputs are floating.
4.5V < STBY < V
CC
/2+2V: The amplifier is DC biased, but no audio output. This allows the input
coupling capacitors to be charged to avoid pop-noise.
V
CC
/2+3V < STBY < V
CC
: The amplifier is operating normally.
Supply voltage ripple rejection
The Supply Voltage Ripple Rejection (SVRR) is measured with an electrolytic capacitor of 150 F on pin SVR.
A larger capacitor value on pin SVR improves the ripple rejection behavior at the lower frequencies.
Built-in protection circuits
As mentioned above, SA7347 has a protection circuit based on multiple temperature measurements: one
measures local temperature of the power stages and another measure the global chip temperature. This
HANGZHOU MICROELECTRONICS CO.,LTD
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SA7347
protection circuit will start to switch off the bias of channel when local temperature reaches approximately 185°C
or global temperature reaches approximately 150°C. As a result, there is low dissipating in the chip. It starts
operating again when the chip temperature drop to same value below the die temperature. But if the temperature
again begins to rise, the SA7347 shuts down again. The process will not stop until the local temperature is under
185°C and the global temperature is under 150°C.
This protects the SA7347 against shorts to ground, to the supply voltage and across the load, and against too
high chip temperatures. However, not that there are abnormal events as shorts to ground, to the supply voltage
and across the load in the chip, the protection circuit should start-up. In fact, just as much as the temperature
does not exceed the critical level, the protection circuit will not operate.
Power Dissipation and Heat Sinking
Proper heat sinking is necessary to ensure that SA7347 will function correctly under all operating conditions. A
heat sink that is too small will cause the die to heat excessively and will result in a degraded output signal as the
thermal protection circuitry begins to operate.
In order to determine the appropriate heat sink for a given application, the power dissipation of the SA7347 in
that application must be known. When the load is resistive, the maximum average power that the IC will be
required to dissipate is approximately:
P
D(MAX)
=4*VS
2
/(2π
2
RL)+PQ
Where VS is the total power supply voltage across the SA7347, RL is the load resistance; PQ is the quiescent
power dissipation of the amplifier. The above equation is only an approximation which assumes an “
ideal”class B
output stage and constant power dissipation in all other parts of the circuit. As an example, if the SA7347 is
operated on a 15V power supply with a resistive load of 4Ω, it can develop up to 13.5W of internal power
dissipation. If the die temperature is to remain below 150°C for ambient temperatures up to 60°C, the total
junction-to-ambient thermal resistance must be less than:
(150°C 60°C)/13.5W
6.7°C /W
Using Rth(j-c) = 1.3°C /W, the sum of the case-to-heat-sink interface thermal resistance and the heat-sink-to-
ambient thermal resistance must be less than 5.4°C/W. The case-to-heat-sink thermal resistance of the HSIP-15
package varies with the mounting method used. A metal-to-metal interface will be about 1°C /W if lubricated, and
about 1.5°C /W if dry.
6.7°C /W-1.3°C /W-1°C /W
4.4°C /W
The thermal requirements can become more difficult when an amplifier is driving a reactive load. For a given
magnitude of load impedance, a higher degree of reactance will cause a higher level of power dissipation within
the amplifier. As a general rule, the power dissipation of an amplifier driving a 60º reactive load (usually
considered to be a worst-case loudspeaker load) will be roughly that of the same amplifier driving the resistive
part of that load. For example, a loudspeaker may at some frequency have an impedance with a magnitude of 8Ω
and a phase angle of 60º. The real part of this load will then be 4Ω, and the amplifier power dissipation will
roughly follow the curve of power dissipation with a 4Ω load.
HANGZHOU MICROELECTRONICS CO.,LTD
Http: www.silan.com.cn
REV:1.1
2007.07.27
Page 5 of 9
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