Overview
The LA4906 is a BTL two-channel power amplifier for
use in car audio systems. It uses a signal-following
switching technique in the power supply for the amplifier
output stage and a newly-developed nonlinear amplifier
that features nonlinear characteristics in the signal system.
These features hold increases in the number of external
components to a minimum, and reduce power dissipation
(and thus heat generation) in the practical operating region
to about 1/2 that of earlier class B amplifier ICs. This can
contribute significantly to miniaturization and weight
reduction in the heat sink and to reduction of the heat
generated within the end product case.
Features
· Power dissipation reduced by 50% (for music at average
power levels, as compared to earlier Sanyo products)
· The number of required signal-following switching
circuits has been reduced to just one circuit for two
channels, reducing the number of external components.
· The output is a pure analog signal; no switching noise
whatsoever appears on the output lines.
· Uses a single-voltage power supply from 8 to 18 V.
· Provides a full range of built-in protection circuits,
including shorting of output pin to V
CC
, shorting of
output pin to ground, overvoltage, and thermal
shutdown protection.
· Built-in standby switch
· Clipping detection function
Package Dimensions
unit: mm
3160-SIP23HZ
Monolithic Linear IC
Ordering number : EN
*
5714
73097HA(OT) No. 5714-1/10
Preliminary
SANYO: SIP23HZ
[LA4906]
SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110 JAPAN
17-W, 2-Channel BTL AF High-Efficiency
Power Amplifier for Car Audio Systems
LA4906
Parameter
Symbol
Conditions
Ratings
Unit
Maximum supply voltage
V
CC
max1
With no signal, t = 1 minute
18
V
V
CC
max2
16
V
Maximum output current
I
O
Peak
Per channel
4.5
A
Allowable power dissipation
Pd max
With an arbitrarily large heat sink
37.5
W
Operating temperature
Topr
35 to +85
°C
Storage temperature
Tstg
40 to +150
°C
Specifications
Absolute Maximum Ratings
at Ta = 25°C
Notes: 1. Set V
CC
and R
L
to be in the range where Pd max does not exceed 37.5 W.
2. The overvoltage protection circuit operates at V
CC
= 26 V or higher.
No. 5714-2/10
LA4906
Parameter
Symbol
Conditions
Ratings
Unit
min
typ
max
Quiescent current drain
I
CC
0
R
L
=
, V
IN
= 0
80
110
150
mA
Standby current
Ist
0
10
µA
Voltage gain
VG
V
O
= 0 dBm
28
30
32
dB
Total harmonic distortion
THD
P
O
= 1 W, LPF = 30 kHz
0.07
0.2
%
Output power
P
O
1
THD = 10 %, RL = 4
14
17
W
P
O
2
THD = 10 %, RL = 2
25
W
Output noise voltage
V
NO
Rg = 0, BPF = 20 Hz to 20 kHz
0.10
0.3
mVrms
Ripple rejection ratio
SVRR
Rg = 0, V
CCR
= 0 dBm,
60
75
dB
BPF = 20 Hz to 20 kHz
Channel separation
CH sep
Rg = 10 k
, V
O
= 0 dBm,
45
60
dB
BPF = 20 Hz to 20 kHz
Input resistance
Ri
21
30
39
k
Output offset voltage
VN offset
Rg = 0
200
+200
mV
Standby on voltage
V
STH
AMP = on, applied through a 10 k
resistor
3
V
CC
V
Clipping detect off current
I
DOFF
THD = 1 %
1
10
µA
Clipping detect on current
I
DON
THD = 10 %
100
150
200
µA
Operating Characteristics
at Ta = 25°C, V
CC
= 13.2 V, R
L
= 4
, f = 1 kHz, RG = 600
, in the recommended circuit
Parameter
Symbol
Conditions
Ratings
Unit
Recommended supply voltage
V
CC
13.2
V
Allowable operating voltage range
V
CC
op
8 to 16
V
Recommended load resistance
R
L
4
Recommended load resistance range
R
L
op
2 to 4
Operating Conditions
at Ta = 25°C
Note: Set V
CC
and R
L
to be in the range where Pd max does not exceed 37.5 W.
Allowable power dissipation, Pd max W
Heat sink thermal resistance,
f
°
C/W
Heat sink area, Sf cm
2
Ambient temperature, Ta °C
With an arbitrarily large heat sink
Al heat sink, t = 1.5 mm
Tightening torque: 39 N·cm
With silicone grease applied.
No. 5714-3/10
LA4906
Technologies for Increased Efficiency Used in the LA4906
· Nonlinear amplifier
The LA4906 adopts a nonlinear amplifier, which has the nonlinear
characteristics shown in Figure 2, in the signal system. The LA4906
dispenses with the lower side switching regulator by using a low 2 V
as the midpoint voltage instead of the 1/2 VCC used in normal
amplifiers.
This nonlinear amplifier is basically formed from a differential
amplifier that has a symmetrical negative feedback circuit. Although
the BTL output stage positive and reverse phase output waveforms
have a half-wave waveform that, when referenced to ground, is
expanded and compressed as shown in Figure 3, the combined
output waveform at the load terminals is identical to that of earlier
products.
· Signal-following switching technique
The LA4906 uses a switching regulator for the power supply for the
amplifier output stage. The LA4906 significantly reduces power
dissipation by having the switching regulator output voltage follow
the signal. Also, the LA4906 restricts the number of switching
regulators required to just one circuit even though it implements a
BTL 2-channel amplifier by using the switching regulator in
combination with the nonlinear amplifier described below. (See
Figure 1.)
Figure 1 Overview Block Diagram
Figure 2 Nonlinear Amplifier
Input/Output Characteristics
Figure 3 Output Waveforms
Figure 4
RL = 4
f = 1 kHz
Rg = 600
With both channels
driven.
Calculated at Pd =
VCC
×
ICC 2 P
O
Regulator
output
Amplifier
output
stage
Nonlinear
amplifier
Loss in the output
transistor
Regulator output (point C)
Regulator output (point C)
Positive phase
output (point A)
Center point
Ground
Reverse phase
output (point B)
Center point
Ground
Waveform between
the outputs
(Between A and B)
Power dissipation, Pd W
Output power, P
O
W
High-efficiency
LA4906
Earlier SANYO
products (class
B amplifiers)
Equivalent Circuit Block Diagram
No. 5714-4/10
LA4906
Pin Voltages
(At V
CC
= 13.2 V, with 5 V applied to STBY through a 10 k
resistor, using a digital voltmeter)
Pin No.
1
2
3
4
5
6
7
8
Pin
IN2
Pre - GND
IN1
BEEP
PWR - GND 1
OUT1
+OUT1
C
Pin voltage (V)
1.36
0
1.36
1.36
0
2.03
2.03
13.0
Pin No.
9
10
11
12
13
14
15
16
Pin
C
V
CC
V
CC
(SW)
SW OUT1
SW OUT2
SW E
SE B
SW - GND
Pin voltage (V)
3.92
13.2
13.2
3.70
3.70
3.73
4.0
0
Pin No.
17
18
19
20
21
22
23
Pin
+OUT2
OUT2
PWR - GND2
D. C
STAND-BY
DDL OUT
ON-TIME
Pin voltage (V)
2.03
2.03
0
12.1
3.21
0
2.81
Standby
switch
Switching
regulator
block
Switch
driver
Standby switch
Ripple filter
(Tokin Co. Ltd.)
(OS capacitor)
*
= Polyester film capacitors
D1
SB40-05J
Flywheel diode
Amplifier output stage
Input amplifier
Input amplifier
Nonlinear amplifier/output stage
Nonlinear amplifier/output stage
TR1
Switching transistor
2SD1668, class S
Muting circuit used
at power on
Popping noise
prevention circuit
Power supply/ground shorting
protection circuit
Overvoltage/thermal
protection circuit
Beep amplifier
*
*
4 to 2
4 to 2
No. 5714-5/10
LA4906
Sample Printed Circuit Board
1. External component descriptions
C1 and C2
· Input capacitors. A value of 2.2 µ F is recommended for these capacitors. Note that the low-frequency area
characteristics can be adjusted by changing f
L
, which is determined by the values of C1 and C2. However, due to
impulse (pop) noise considerations, the value of C1 and C2 should not exceed 3.3 µF when C4 is 22 µF.
C3
· Beep amplifier input capacitor. A value the same as that of C1 and C2 is used. If the beep function is not used, connect
the beep input to PRE-GND through C3.
C4
· Set the amplifier turn-on time. A value of 22 µF is recommended. (This will result in a turn-on time of about 0.7
second.) The on time is proportional to the value of this capacitor, and any value may be used. However, due to
impulse (pop) noise considerations, a value of 22 µF or larger should be used.
C5, C6, C7, and C8
· Oscillation prevention capacitors. Polyester film (Mylar) capacitors with good temperature characteristics must be used.
(These are used together with R1, R2, R3, and R4.) We recommend values of 0.1 µF or higher for these capacitors
since the stability will differ somewhat depending on the printed circuit board layout actually used.
C9
· Decoupling capacitor (ripple filter)
C10
· Power-supply capacitor
C11
· Oscillation prevention capacitor for the switching regulator. A value of 1500 pF is recommended.
C12
· Switching regulator output smoothing capacitor. The LA4906 adopts a self-excited switching regulator technique. The
value of this capacitor must be optimized, since it influences both the self-excitation stability and the regulator
efficiency. We recommend using a 2.2-µF 25-V OS (Organic Semiconductor) capacitor with a low series resistance
and good temperature characteristics. Note that for the same reason a 2.2-
1/2-W resistor should be used for the
associated resistor R6.
R5
· Standby switch current limiter resistor. A value of 10 k
is recommended. (When the voltage applied to the standby
switch is in the range 3 to 13.2 V.) Note that this resistor cannot be removed from this circuit.
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