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Ordering number : EN6631A
LA4625
Monolithic Linear IC
2-channel 13.5W BTL Audio Power
Amplifier
http://onsemi.com
Overview
The LA4625 is a 2-channel general-purpose BTL audio power amplifier provided in a miniature package. It was
designed for the best possible audio quality and features an extended low band roll-off frequency provided by a
newly-developed NF circuit that does not require an external capacitor. Furthermore, crosstalk, which can cause
muddiness in the audio output, has been significantly reduced by both circuit and wiring pattern improvements. Thus
this amplifier can provide powerful lows and clear highs.
Note that this device is pin compatible with the 20W×2-channel LA4628, and allows end products differentiated by
their power rating to share the same printed circuit board.
Features
Total output : 13.5W+13.5W (at VCC = 12V, RL = 4Ω, THD = 10%)
PMPO reference data : 115W×2 (VCC = 20V, RL = 4Ω)
High-fidelity design (fL < 10Hz, fH = 130kHz)
Extremely low impulse noise levels
An arbitrary amplifier startup time can be set up with external components.
Full complement of built-in protection circuits (includes circuits that protect against shorting to VCC, shorting to
ground, load shorting, overvoltages and excessive temperatures)
Specifications
Maximum Ratings at Ta = 25°C
Parameter
Maximum supply voltage
Maximum output current
Allowable power dissipation
Operating temperature
Storage temperature
Symbol
VCC max
IO peak
Pd max
Topr
Tstg
Conditions
No signal
Per channel
With an arbitrarily large heat sink
Ratings
24
3.5
32.5
-20 to +85
-40 to +150
Unit
V
A
W
°C
°C
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating
Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability.
Semiconductor Components Industries, LLC, 2013
May, 2013
O0808 MS JK/92900RM (OT) No.6631-1/8

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LA4625
Operating Conditions at Ta = 25°C
Parameter
Symbol
Conditions
Recommended supply voltage
VCC
Recommended load resistance range
RL op
Allowable operating supply voltage
VCC op
Note : With VCC, RL, and the output level in ranges such that the Pd max for the heat sink used is not exceeded.
Ratings
12
4 to 8
7.2 to 20
Unit
V
Ω
V
Electrical Characteristics at Ta = 25°C, VCC = 12V, RL = 4Ω, f = 1kHz, Rg = 600Ω
Parameter
Quiescent current
Standby mode current drain
Voltage gain
Total harmonic distortion
Output power
Output offset voltage
Output noise voltage
Ripple rejection ratio
Channel separation
Input resistance
Standby pin applied voltage
Symbol
ICCO
Ist
VG
THD
PO1
VN offset
VNO
SVRR
CHsep
Ri
VST
Conditions
Rg = 0
Standby mode (amplifier off), with no power
supply capacitor.
VO = 0dBm
PO = 1W, Filter = FLAT
THD = 10%
Rg = 0
Rg = 0, BPF = 20Hz to 20kHz
Rg = 0, VR = 0dBm, fR = 100Hz
Rg = 10kΩ, VO = 0dBm
Amplifier on
(applied through an external 10kΩ resistor)
min
65
38
10
-300
40
50
21
2.5
Ratings
typ
120
10
40
0.06
13.5
0.1
50
60
30
max
240
60
42
0.2
+300
0.5
39
VCC
Unit
mA
µA
dB
%
W
mV
mV
dB
dB
kΩ
V
Package Dimensions
unit : mm (typ)
3113B
Pd max -- Ta
35 Infinite heat sink
32.5
AI heat sink Mounting
torque 39N • cm Flat
30 washer Silicone grease
25 θf = 3˚C/W
applied
20.83 θf = 4˚C/W
20
θjc = 2˚C/W
15
13.9
θf = 7˚C/W
10.4 θf = 10˚C/W
10
5
3.1
Νο Fin
0
-20 0 20 40 60 80 100 120 140 160
Ambient temperature, Ta -- ˚C
No.6631-2/8

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Block Diagram
C2
100μF/16V
+
C1+ 1
2.2μF
10V
2
RIPPLE
FILTER
+
IN
PRE GND
3
OFF
Standby
SW
R1
ON 10KΩ
+5V
4
C4+
2.2μF
10V
IN2
6
BIAS
CIRCUIT
STANDBY
SW
+
IN
PREDRIVER
PREDRIVER
PREDRIVER
PREDRIVER
POP NOISE
PREVENTION
CIRCUIT
LA4625
VCC
+
C5
14
OUTPUT PIN TO VCC
SHORT PROTECTOR
POWER
POWER
LOAD SHORT
PROTECTOR
OVER VOLTAGE /
SURGE PROTECTOR
THERMAL
SHUT DOWN
VCC
POWER
POWER
LOAD SHORT
PROTECTOR
13 -OUT1
C6**
POWER
GND1
12
R2
R3
C7**
11
+OUT1 +
RL
4Ω
OUTPUT PIN TO GND
SHORT PROTECTOR
*(*POLYESTER FILM
CAPACITOR)
OUTPUT PIN TO GND
SHORT PROTECTOR
9 -OUT2
C8**
POWER
GND2
10
R4
R5
8 C9**
+OUT2 +
RL
4Ω
OUTPUT PIN TO VCC
SHORT PROTECTOR
5
+
C3
7
+
C10
C3
Sets the amplifier starting time
(Approximately 0.6 seconds when 33μF)
C10
Impulse noise reduction
(Note : The device’s ability to withstand shorting
to VCC or shorting to ground when VCC is around
16V may be reduced as the value of this
capacitor is increased. We recommend 0.47μF.)
No.6631-3/8

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LA4625
Pin Voltages
VCC = 12V, with 5V applied to STBY through a 10kΩ resistor, RL = 4Ω, Rg = 0
Pin No.
1
2
3
4
5
Pin name
IN1
DC
PRE-GND
STBY
ON TIME
Pin voltage
1.46V
5.18V
0V
3.21V
2.26V
6
IN2
1.46V
7
POP
2.05V
Pin No.
Pin name
Pin voltage
8
+OUT2
5.21V
9
OUT2
5.21V
10
PWR-GN
0V
11
+OUT1
5.21V
12
PWR-GN
0V
13
OUT1
5.21V
14
VCC
12V
External Components
C1 and C4: Input capacitors. A value of 2.2μF is recommended. Determine the polarity based on the DC potential of
the circuit connected directly to the LA4625 front end. Note that the low band response can be adjusted by
varying fL with the capacitors C1 and C4.
C2 : Decoupling capacitor (ripple filter)
C3 : Sets the amplifier starting time, which will be approximately 0.6 seconds for a value of 33μF. The starting
time is proportional to the value of this capacitor, and can be set to any desired value.
C5 : Power-supply capacitor
C6, C7, C8, and C9 :
Oscillation prevention capacitors. Use polyester film capacitors (Mylar capacitors) with excellent
characteristics. (Note that the series resistors R2, R3, R4, and R5 are used in conjunction with these
capacitors to achieve stable amplifier operation.) A value of 0.1μF is recommended.
C10 : Impulse noise reduction capacitor. A value of 0.47μF is recommended. Caution is required when selecting
the value for this capacitor, since increasing its value influences the operation of the circuits that protect
against shorting the amplifier output pins to VCC or to ground when higher VCC voltages (approximately
16V or higher) are used.
R1 : Standby switch current limiting resistor. A value of 10kΩ is recommended when a voltage in the range 2.5 to
12V will be applied as the standby switching voltage. Note that this resistor is not optional: it must be included.
IC Internal Characteristics and Notes
1. Standby function
Pin 4 is the standby switch. A voltage of 2.5V or
higher must be applied through an external resistor to
turn the amplifier on.
If a voltage of over 12V will be applied as the
standby mode switching voltage, use the following
formula to determine the value of R1 so that the
current entering at pin 4 remains under 500μA.
Pin 4 Internal Equivalent Circuit
500μA or lower
4
R1
10kΩ
Applied standby
voltage
About 1.4V
(2VBE)
R1 =
<applied voltage> − 1.4
500μA
10kΩ
2. Muting function
Pin 5 connects the capacitor that determines the starting time to prevent impulse noise. It can also be used to mute
the amplifier output by shorting pin 5 to ground. When this function is used, the recovery time depends on C3.
3. Impulse noise improvements
While the LA4625 achieves a low level of impulse noise, if even further reductions in impulse noise at power
on/off (and when switching into or out of standby mode) a 0.47μF capacitor may be inserted between pin 7 and the
PRE GND pin (pin 3). (Pin 7 is the output amplifier bias pin. Since the ability to withstand shorting the output pins
to VCC or ground is reduced for supply voltages over 16V if the pin 7 capacitance is large, we recommend a value
of 0.47μF or lower for this capacitor.)
No.6631-4/8

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LA4625
4. Protection circuits
Due to the system structure of the protection circuit for shorts to VCC or ground, if there is a DC resistance
between the amplifier output pins and ground, the protection circuit may operate when power is first applied and
the amplifier may fail to turn on. The basic design approach we recommend is not to adopt any designs in which
there is a DC resistance between the amplifier outputs and ground.
The LA4625 includes a built-in thermal protection circuit to prevent the IC from being damaged or destroyed if
abnormally high temperatures occur. This thermal protection circuit gradually reduces the output if the IC
junction temperature (Tj) reaches the range 170 to 180°C due to inadequate heat sinking or other problem. If the
temperature falls, the amplifier will restart automatically.
The LA4625 also includes other protection circuits. Use of these circuits also requires care during end product
design and testing.
5. Other notes
The LA4625 is a BTL power amplifier. When testing this device, the ground systems for the test equipment
connected to IC inputs, and that for the test equipment connected to IC outputs, must be isolated. Do not use a
common ground.
Printed Circuit Pattern
(copper foil side)
No.6631-5/8