Overview
The LA4905 is a BTL 2-channel power amplifier IC for
use in car audio systems. Increases in the number of
external components are held to a minimum by adopting
both a signal-following type switching scheme in the
amplifier's output stage power supply, and a newly-
developed nonlinear amplifier that has nonlinear
characteristics in the signal system. The power dissipation
(thermal loss) in the actual operating range has been
reduced to about 1/2 that of earlier class B amplifier ICs.
This contributes significantly to miniaturization of the heat
sink and to reduction of heating within the set.
Features
Power dissipation reduced by 50% (When average
music power is measured, and when compared to earlier
Sanyo products.)
The number of required signal follower circuits has been
reduced to a single circuit for two channels, allowing the
number of external components to be reduced.
The output is a pure analog signal: no switching noise is
output to the output lines.
Operates on an 8 to 18-V single-voltage power supply.
Full complement of built-in protection circuits (shorting
to the power supply, shorting to ground, overvoltage,
and thermal protection)
Built-in standby switch
Package Dimensions
unit: mm
3160-SIP23HZ
Monolithic Linear IC
Ordering number : EN5504
83096HA (OT) No. 5504-1/10
SANYO: SIP23HZ
[LC4905]
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 Stereo Systems
LA4905
Parameter
Symbol
Conditions
Ratings
Unit
Maximum supply voltage
V
CC
max1
No input, t = 1 minute
24
V
V
CC
max2
18
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
Maximum Ratings
at Ta = 25C
Notes: 1. Set VCC and RL in the range where Pd max does not exceed 37.5 W.
2. The overvoltage protection circuit operates when VCC is 20 V or higher.
No. 5504-2/10
LA4905
Parameter
Symbol
Conditions
Ratings
Unit
Recommended supply voltage
V
CC
13.2
V
Allowable operating supply voltage range
V
CC
op
8 to 18
V
Recommended load resistance
R
L
4
Recommended load resistance range
R
L
op
2 to 4
Operating Conditions
at Ta = 25C
Operating Characteristics
at Ta = 25C, V
CC
= 13.2 V, R
L
= 4
, f = 1 kHz, Rg = 600
, in the recommended circuit
Notes:Set VCC and RL in the range where Pd max does not exceed 37.5 W.
Parameter
Symbol
Conditions
min
typ
max
Unit
Quiescent current
Icco
R
L
=
, V
IN
= 0
80
110
150
mA
Standby current
Ist
0
10
A
Voltage gain
VG
V
O
= 0 dBm
38
40
42
dB
Total harmonic distortion
THD
P
O
= 1W, LPF = 30 kHz
0.07
0.2
%
Output power 1
P
O
1
THD = 10%, R
L
= 4
14
17
W
P
O
2
THD = 10%, R
L
= 2
25
W
Output noise voltage
V
NO
Rg = 0, BPF = 20 Hz to 20 kHz
0.15
0.3
mVrms
Ripple rejection ratio
SVRR
Rg = 0, V
CCR
= 0 dBm, BPF = 20 Hz to 20 kHz
60
70
dB
Channel separation
CHsep
Rg = 10 k
, V
O
= 0 dBm, BPF = 20 Hz to 20 kHz
45
55
dB
Input resistance
Ri
21
30
39
k
Output offset voltage
VN offset
Rg = 0
300
+300
mV
Standby on voltage
V
STH
AMP = on, applied through a 10 k
resistor
3
V
CC
V
LA4905 High-Efficiency Technology
(1) Signal-following switching scheme
The LA4905 adopts a switching regulator scheme in
the power supply applied to the amplifier output stage.
The LA4905 power dissipation is reduced significantly
by having the output voltage of the switching regulator
follow the input signal. Furthermore, in combination
with the nonlinear amplifier scheme described below,
the LA4905 design reduces the number of switching
regulators to merely one circuit even though it is a
BTL 2-channel amplifier. (See Figure 1.)
(2) Nonlinear amplifier
The LA4905 adopts a nonlinear amplifier that has the
nonlinear characteristics shown in Figure 2 in the
amplifier signal system. This scheme does not use the
center point voltage of 1/2 VCC used in normal
amplifiers, but instead uses a voltage about 2 V lower.
This allows the design to dispense with the lower side
switching regulator.
This nonlinear amplifier has a structure based on a
differential amplifier that has symmetric negative
feedback circuits. Although the BTL output stage
positive and negative phase output waveform is a half-
wave waveform that is expanded and compressed as
shown in Figure 3, the combined output waveform at
the negative load terminal is identical to that output by
earlier products.
No. 5504-3/10
LA4905
Equivalent Circuit Block Diagram
No. 5504-4/10
LA4905
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 OUT 1
SW OUT 2
SW E
SW 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
+OUT 2
OUT 2
PWR-GND 2
D. C
STAND-BY
N. C
ON-TIME
Pin voltage (V)
2.03
2.03
0
12.1
3.21
0
2.81
Pin Voltages
V
CC
= 13.2 V, 5 V applied to STBY through a 10-k
resistor, using a digital voltmeter
Sample Printed Circuit Board Pattern
1. External Component Functions
C1, C2
Input capacitors; recommended value: 2.2 F. Note that the low-frequency band can be adjusted by changing
the values of C1 and C2, since fL depends on their value, although the value must not exceed 3.3 F (when
C4 is 22 F) due to pop noise considerations.
C3
Beep amplifier input capacitor. Use the same value as that used for C1 and C2. Connect the beep amplifier to
PRE-GND through C3 if the beep function is not used.
C4
Amplifier power-on delay time setting capacitor; recommended value: 22 F. At the recommended value, the
amplifier will turn on in about 0.7 second after power is applied. The delay time is proportional to the
capacitance and can be set to an arbitrary value. However, a value of 22 F or larger should be used due to
pop noise considerations.
C5, C6,
Oscillation prevention capacitors. Use capacitors with excellent temperature characteristics such as polyester
film or Mylar capacitors. These capacitors function in conjunction with R1, R2, R3, and R4. We recommend
using capacitors of 0.1 F or larger, since the stability varies somewhat depending on the printed circuit
board layout.
C9
Decoupling capacitor (ripple filter)
C10
Power-supply capacitor
C11
Switching regulator oscillation prevention capacitor; recommended value: 1500 pF.
C12
Switching regulator output smoothing capacitor. The LA4905 adopts a self-excitation switching regulator
scheme. Since this capacitor influences the stability of the self-excitation and the regulator efficiency, there is
an optimal value. We recommend the use of a 2.2-F, 25-V OS capacitor with good temperature
characteristics. Note that a 2.2-
, 1/2-W resistor should be used for R5 for the same reason.
R5
Standby switch current limiting resistor; recommended value: 10 k
.
(When the voltage applied to the standby switch is between 3 and 13.2 V.) Note that this resistor cannot be
removed. See the section "Standby Function" elsewhere in this document.
TR1
External switching transistor. We recommend using a 2SD1668 of rank S. A 2SD1667 of rank S may be used if
the application is designed to handle 4-
loads (R
L
). A heat sink must be provided along with that for the IC.
D1
Flywheel diode that takes up the coil energy. We recommend using an SB40-05J, which is a Schottky barrier
diode with a low V
F
.
An SB10-05A2 may be used if the application is designed to handle 4-
loads (R
L
). A joint heat sink is not
required.
L1
We recommend the use of the HP-022Z 180-H coil manufactured by Tokin, Ltd. The 200-H HP-011Z may
be used if the application is designed to handle 4-
loads (R
L
).
No. 5504-5/10
LA4905
C7, C8
2. IC Internal Characteristics and Usage Notes
Switching Regulator
To reduce power dissipation, the LA4905 includes a signal-following type switching regulator. When there is no input
signal, the self-excited oscillator operates at about 100 kHz.
It is desirable for the amplifier block to be separated as far as possible from the tuner block to prevent interference from
extraneous radiation within the set. Also, when designing the printed circuit board layout, the pattern lines for the
switching regulator components should be made as short and as broad as possible.
To prevent degradation of the characteristics of the LA4905 itself, the separation between the switching regulator
components and the IC input block (the input block pattern, the input capacitors, and the beep capacitor) should be at
least 1.5 cm.
Standby Function
Pin 21 is the standby switch pin. The amplifier is turned
on by applying a voltage of about 3 V or higher through
an external resistor (R1).
The value of R1 must be determined, using the following
formula, so that the pin 5 influx current remains under
500 A if a voltage in excess of 13.2 volts is applied as
the standby switch voltage.
applied voltage 1.4 V
R1 = -------------------- 10 k
500 A
BEEP Pin (pin 4)
If the BEEP pin is used, use a value for R102 shown in
the figure that is under 100
and is as small as possible
to prevent degradation of the IC output noise voltage
(VNO).
Protection Circuits
The LA4905 includes a built-in thermal protection
circuit to prevent destruction or degradation if the IC
generates abnormal amounts of heat. The thermal
protection circuit controls the IC so that the output is
gradually lowered if the IC junction temperature (Tj)
increases to about 160C due to an insufficient heat sink
or other reason.
The overvoltage protection circuit operates if the V
CC
voltage exceeds a value of about 20 volts.
Although the LA4905 includes an on-chip protection
circuit for shorts to V
CC
and shorts to ground, it does not
include a load shorted protection circuit. The idea behind
this design is that the thermal protection circuit will
protect the IC against load shorting. However, since load
shorting can also cause heating in external transistors and
coils, designs should take load shorting into
consideration.
Other Notes
Pin 22 is an NC pin, and is not connected within the
package.
No. 5504-6/10
LA4905
No. 5504-7/10
LA4905
No. 5504-8/10
LA4905
No. 5504-9/10
LA4905
No. 5504-10/10
LA4905
This catalog provides information as of August, 1996. Specifications and information herein are subject to
change without notice.
s
No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace
equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of
which may directly or indirectly cause injury, death or property loss.
s
Anyone purchasing any products described or contained herein for an above-mentioned use shall:
Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and
distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all
damages, cost and expenses associated with such use:
Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on
SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees
jointly or severally.
s
Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for
volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied
regarding its use or any infringements of intellectual property rights or other rights of third parties.
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