LM4734
3 Channel 20W Audio Power Amplifier with Mute and
Standby
General Description
The LM4734 is a three channel audio amplifier capable of
typically delivering 20W per channel of continuous average
output power into a 4
or 8 load with less than 10%
THD+N from 20Hz - 20kHz.
The LM4734 has short circuit protection and a thermal shut
down feature that is activated when the die temperature
exceeds 150C. The LM4734 also has an under voltage lock
out feature for click and pop free power on and off.
Each amplifier of the LM4734 has an independent smooth
transition fade-in/out mute and a power conserving standby
mode. The mute and standby modes can be controlled by
external logic.
The LM4734 has a wide supply operating supply range from
10V -
30V allowing for lower cost unregulated power
supplies to be used.
The LM4734 can easily be configured for bridge or parallel
operation for higher power and bi-amp solutions.
Key Specifications
j
Output Power/Channel with 10% THD+N,
1kHz into 4
or 8
20W (typ)
j
THD+N at 3x1W into 8
, 1kHz
0.03% (typ)
j
Mute Attenuation
110dB (typ)
j
PSRR
64dB (typ)
j
Slew Rate
18V/s (typ)
Features
n
Low external component count
n
Quiet fade-in/out mute mode
n
Low power standby mode
n
Wide supply range: 20V - 60V
Applications
n
Audio amplifier for component stereo
n
Audio amplifier for compact stereo
n
Audio amplifier for home theater in a box (HTB)
n
Audio amplifier for high-end and HD TVs
Typical Application
SPiKe
TM
Protection and Overture
TM
are trademarks of National Semiconductor Corporation.
200898D2
FIGURE 1. Typical Audio Amplifier Application Circuit
February 2004
LM4734
3
Channel
20W
Audio
Power
Amplifier
with
Mute
and
Standby
2004 National Semiconductor Corporation
DS200898
www.national.com
Absolute Maximum Ratings
(Notes 1,
2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage |V
+
| + |V
-
|
60V
Common Mode Input Voltage
(V
+
or V
-
) and
|V
+
| + |V
-
|
54V
Differential Input Voltage (Note 12)
54V
Output Current
Internally Limited
Power Dissipation (Note 3)
125W
ESD Susceptability (Note 4)
2.0kV
ESD Susceptability (Note 5)
200V
Junction Temperature (T
JMAX
) (Note 9)
150C
Soldering Information
TA Package (10 seconds)
260C
Storage Temperature
-40C to +150C
Thermal Resistance
JA
30C/W
JC
1.0C/W
Operating Ratings
(Notes 1, 2)
Temperature Range
T
MIN
T
A
T
MAX
-20C
T
A
+85C
Supply Voltage |V
+
| + |V
-
|
20V
V
TOTAL
60V
Electrical Characteristics
(Notes 1, 2)
The following specifications apply for V
+
= +21V, V
-
= -21V, and R
L
= 8
unless otherwise specified. Limits apply for T
A
=
25C.
Symbol
Parameter
Conditions
LM4734
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
|V
+
| + |V
-
|
Power Supply Voltage (Note
10)
GND - V
-
9.5V
18
20
60
V (min)
V (max)
A
M
Mute Attenuation
V
MUTE
= 2.5V
110
dB
P
O
Output Power (RMS)
THD+N = 10% (max), f = 1kHz
|V
+
| = |V
-
| = 17V, R
L
= 4
|V
+
| = |V
-
| = 21V, R
L
= 8
20
20
15
15
W (min)
W (min)
THD+N = 1% (max), f = 1kHz
|V
+
| = |V
-
| = 17V, R
L
= 4
|V
+
| = |V
-
| = 21V, R
L
= 8
17
18
W
W
THD+N
Total Harmonic Distortion +
Noise
P
O
= 1W, f = 1kHz
A
V
= 26dB
|V
+
| = |V
-
| = 17V, R
L
= 4
|V
+
| = |V
-
| = 21V, R
L
= 8
0.05
0.03
%
%
X
talk
Channel Separation (Note 11)
P
O
= 10W, f = 1kHz
65
dB
P
O
= 10W, f = 10kHz
55
dB
SR
Slew Rate
V
IN
= 1.414V
RMS
, t
rise
= 2ns
18
V/s
I
DD
Total Quiescent Power Supply
Current
V
CM
= 0V, V
O
= 0V, I
O
= 0A
V
STANDBY
= GND, Standby = Off
V
STANDBY
= 5V, Standby = On
75
8
120
10
mA (max)
mA (max)
V
OS
Input Offset Voltage
V
CM
= 0V, I
O
= 0mA
2.0
15
mV (max)
I
B
Input Bias Current
V
CM
= 0V, I
O
= 0mA
0.2
A
PSRR
Power Supply Rejection Ratio
V
+
= 21V + V
RIPPLE
(1V
RMS
),
f
RIPPLE
= 120Hz Sine, V
-
= 21V
DC
75
dB
V
-
= 21V + V
RIPPLE
(1V
RMS
),
f
RIPPLE
= 120Hz Sine, V
+
= 21V
DC
64
dB
A
VOL
Open Loop Voltage Gain
|V
+
| = |V
-
| = 21V, R
L
= 2k
V
O
= 15V
110
dB
e
IN
Input Noise
IHF-A-Weighting Filter,
R
IN
= 600
(Input Referred)
2.0
V
LM4734
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3
Electrical Characteristics
(Notes 1, 2) (Continued)
The following specifications apply for V
+
= +21V, V
-
= -21V, and R
L
= 8
unless otherwise specified. Limits apply for T
A
=
25C.
Symbol
Parameter
Conditions
LM4734
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
Standby
V
IL
V
IH
Standby Low Input Voltage
Standby High Input Voltage
Play Mode
Standby Mode
2.0
0.8
2.5
V (max)
V (min)
Mute
V
IL
V
IH
Mute Low Input Voltage
Mute High Input Voltage
Play Mode
Mute Mode
2.0
0.8
2.5
V (max)
V (min)
Note 1: All voltages are measured with respect to the ground pins, unless otherwise specified.
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit
is given; however, the typical value is a good indication of device performance.
Note 3: The maximum power dissipation must be de-rated at elevated temperatures and is dictated by T
JMAX
,
JC
, and the ambient temperature T
A
. The maximum
allowable power dissipation is P
DMAX
= (T
JMAX
-T
A
)/
JC
or the number given in the Absolute Maximum Ratings, whichever is lower. For the LM4734, T
JMAX
= 150C
and the typical
JC
is 1.0C/W. Refer to the DETERMINING THE CORRECT HEAT SINK section for more information.
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Machine Model: a 220pF - 240pF discharged through all pins.
Note 6: Typical specifications are measured at 25C and represent the parametric norm.
Note 7: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 9: The maximum operating junction temperature is 150C. However, the instantaneous Safe Operating Area temperature is 250C.
Note 10: V
-
must have at least - 9.5V at its pin with reference to GND in order for the under-voltage protection circuitry to be disabled. In addition, the voltage
differential between V
+
and V
-
must be greater than 14V.
Note 11: Cross talk performance was measured using the demo board shown in the datasheet. PCB layout will affect cross talk. It is recommended that the input
and output traces be separated by as much distance as possible. Return ground traces from outputs should also be independent back to sinlge ground point and
use as wide of traces as possible.
Note 12: The Differential Input Voltage Absolute Maximum Rating is based on supply voltages V
+
= 27V and V
-
= - 27V.
Note 13: The TA27A is a non-isolated package. The package's metal back and any heat sink to which it is mounted are connected to the V
-
potential when using
only thermal compound. If a mica washer is used in addition to thermal compound,
CS
(case to sink) is increased, but the heat sink will be electrically isolated from
V
-
.
LM4734
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