LA4555.PDF

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LA4555
Ordering number:ENN1697B
Monolithic Linear IC
LA4555
2-Channel AF Power Amplifier
for Radio, Tape Recorder Use
Features
• Low quiescent current.
• On-chip 2 channels permitting use in stereo and bridge
amplifier applications.
• High output.
• Minimum number of external parts required.
(9 pcs. munimum)
• Good ripple rejection (at steady state).
• Soft tone at the output saturation mode.
• Good channel separation.
• Easy thermal design.
• Small pop noise at the time of power supply ON/OFF.
Package Dimensions
unit:mm
3022A-DIP12F
[LA4555]
12
7
1
5.12
6
19.4
0.5
3.6
1.3
Specifications
Absolute Maximum Ratings at Ta = 25˚C
0.81
2.54
SANYO : DIP12F
P
S
C
R
U
M
s
v
V C
m
1
V
A
p
d
P
m
W
p
r
P
(
s
p
c
4W
O
t
T
–
t
+
˚C
˚C
S
t
T
–
t
+
Operating Conditions at Ta = 25˚C
P
S
C
R
U
R
s
v
V C
6
9
V
S
6
2
t
8
W
L
r
R L
B
6
4
t
8
W
S
9
4
t
8
W
B
9
8
W
O
v
r
V C o
3
t
1
V
Any and all SANYO products described or contained herein do not have specifications that can handle
applications that require extremely high levels of reliability, such as life-support systems, aircraft’s
control systems, or other applications whose failure can be reasonably expected to result in serious
physical and/or material damage. Consult with your SANYO representative nearest you before using
any SANYO products described or contained herein in such applications.
SANYO assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges,or other
parameters) listed in products specifications of any and all SANYO products described or contained
herein.
SANYO Electric Co.,Ltd. Semiconductor Company
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN
21800TN (KT)/90196RM/O147KI/5275MW, TS No.1697–1/10
11028144.006.png 11028144.007.png 11028144.008.png
LA4555
Operating Characteristics at Ta = 25˚C, V CC =9V, f=1kHz, Rg=600
W
, R L =4
W
, ( ) : R L =8
W
,
See specified Test Circuit.
R
P
S
C
U
m
t
m
Q
c
I
S
9
1
3
m
S
6
1
m
V
g
V
R
V
I
=
4
5
5
d
V
g
d
D
V
R
V
I
=
±
d
T
6
S
0
1
W
T
B
2
W
O
p
P O
T
9
S
1
2
W
T
B
(
W
T
h
d
T
P O
=
0
1
%
I
r
r
2
3
k W
R
0
1
m
O
n
v
V N
R
W
0
2
m
R
r
R
R
f
V
R
=
4
4
d
C
C
R
W
,
f
V
4
5
d
Equivalent Circuit Block Diagram
Sample Application Circuit : Stereo Use
No.1697–2/10
11028144.009.png
LA4555
Sample Printed Circuit Pattern (Cu-foiled side)
Sample Application Circuit : Bridge Amplifier Use 1
Sample Application Circuit : Bridge Amplifier Use 2
Description of External Parts
C1 (C2) : Feedback capacitor. The low cutoff frequency is determined by the following formula.
fL : Low cutoff frequency
Rf : Feedback resistance
Since this capacitor as well as decoupling capacitor affects the starting time, the capacitor value must be fixed
with the necessary low frequency band fully considered.
C3 (C4) : Bootstrap capacitor. The output at low frequencies depends on this capacitor. Decreasing the capacitor value
lowers the output at low frequencies. A capacitor value of 47
1
2
p
C1Rf
F or more is required.
C5 (C6) : Oscillation blocking capacitor. Use a polyester film capacitor that is good in high frequency response and
temperature characteristic. The use of an electrolytic capacitor, ceramic capacitor may cause oscillation to
occur at low temperatures.
m
Continued on next page.
No.1697–3/10
fL=
11028144.001.png
LA4555
Continued from preceding page.
C7 (C8) : Output capacitor. The low cutoff frequency is determined by the following formula.
fL : Low cutoff frequency
RL : Load resistance
To make the low frequency response in the bridge amplifier mode identical with that in the stereo mode, the
capacitor value must be doubled.
fL=
1
2
p
C7RL
C9 :
Decoupling capacitor. Used for the ripple filter. Since the rejection effect is saturated at a certain capacitor
value, it is meaningless to increase the capacitor value more than needed. This capacitor, being also used for
the time constant of the muting circuit, affects the starting time.
C10 :
Power source capacitor.
Application Circuits
Voltage gain adjust
· Stereo mode
The voltage gain is determined by on-chip resistor R1 (R2) and external feedback resistor Rf as follows :
VG=20 log [dB]
R1
Rf1+R2
Any voltage gain can be obtained by external
resistor Rf.
· Bridge amplifier 1 mode
Since point A is at the same potential as Vi and point B is a virtual GND point,
Vo 1
»
R1
R2+R4+Rf1+Rf2
Vo 2
»
–R3
R2+R4+Rf1+Rf2
Vo = Vo1 – Vo2 = Vi
R1+R3
R2+R4+Rf1+Rf2
VG=20 log =20log [dB]
Vo
Vi
R1+R3
R2+R4+Rf1+Rf2
Assuming R2=R4=50
W
, R1=R3=20k
W
and Rf1=Rf2, the voltage gain is obtained by :
VG=20 log [dB]
R1
Rf1+R2
· Bridge amplifier 2 mode
The CH1 is a noninverting amplifer and the CH2 is an inverting amplifier. The total voltage gain, being apparently
higher than that of the CH1 by 6dB, is approximately calculated by the following formula.
VG=20log R2/R1+6 (dB)
To reduce the voltage gain, Rf is connected and the following formula is used.
VG=20log R2/Rf+R1+6 (dB)
No.1697–4/10
Vi
Vi
11028144.002.png
LA4555
Proper Cares in Using LA4555-Applied Set
1. If the transformer regulation is not as specified, the supply voltage drops momentarily when the motor is an AC-
powered set is turned ON. In this case, hum noise may be generated. So, be careful of the transformer regulation.
2. DC muting
To apply DC muting by controlling the NF pin, it is recommended to use
the circuit configuration shown right. The potential at point A is set to 3.5
to 4V.
3. Pop noise
If pop noise generated at the time of power ON/OFF disturbs you, con-
nect a resistor of approximately 620
W
Thermal Design
Since the DIP-12F package is such that the Cu-foiled area of the printed circuit board is used to dissipate heat, make the
Cu-foiled area in the vicinity of the heat sink of the IC as large as possible when designing the printed circuit board. The
use of the Cu-foiled area indicated by shading in the above-mentioned sample printed circuit pattern makes it possible
to dissipate more heat. Power dissipation Pd is increased depending on the supply voltage and load. So, it is recom-
mended to use the printed circuit board together with the heat sink. The following is a formula to be used to calculate Pd
(for stereo use). For AC power supply, however, it is recommended to actually measure Pd on the transformer of each
set. For bridge amplifier use, Pd is calculated at 1/2 of the load.
(1) DC power supply
Pd max= + Icco · V CC (For stereo use) ..... (1)
2 R L
(2) AC power supply
V CC2 : Supply voltage at quiescent mode
V CC (Pd) : Supply voltage at Pd max
V CC 1
: Supply voltage at maximum output
r
: Voltage regulation V CC2 – V CC1
V CC1
Icco
: Quiescent current
Pd max= + Icco · V CC (Pd) (For stereo use) .............. (2)
2 R L
where
(1+r) V CC1
r · V CC1
V CC (Pd)=
1+
Ö
2 ·
p
· R L
´
Ö
R L
Po max
Example of Heat Sink Mounting Method
The heat sink must be of such a shape as to be able to dissipate heat from the IC plastic area and fin area and is soldered to
the printed circuit board as shown below. For the size of the heat sink, refer to the Pd – Ta characteristic. The material of the
heat sink is recommended to be copper or iron which is solderable. It is recommended to apply silicone grease to the IC
plastic area to reduce thermal resistance between the heat sink and the IC plastic area.
Example of Heat Sink Mounting
No.1697–5/10
across the middle point and GND.
4. Slider contact noise of variable resistor
Since the input circuit uses PNP transistors, no input coupling capacitor is
required. However, if slider contact noise of the variable resistor presents
any problem, connect a capacitor in series with input.
V CC 2
p
V CC (Pd) 2
p
11028144.003.png 11028144.004.png 11028144.005.png

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