LM4674
Filterless 2.5W Stereo Class D Audio Power Amplifier
General Description
The LM4674 is a single supply, high efficiency, 2.5W/
channel, filterless switching audio amplifier. A low noise
PWM architecture eliminates the output filter, reducing ex-
ternal component count, board area consumption, system
cost, and simplifying design.
The LM4674 is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing from a single 5V supply, the device is capable of deliv-
ering 2.5W/channel of continuous output power to a 4
load
with less than 10% THD+N. Flexible power supply require-
ments allow operation from 2.4V to 5.5V.
The LM4674 features high efficiency compared to conven-
tional Class AB amplifiers. When driving and 8
speaker
from a 3.6V supply, the device features 85% efficiency at P
O
= 500mW. Four gain options are pin selectable through the
GAIN0 and GAIN1 pins.
Output short circuit protection prevents the device from be-
ing damaged during fault conditions. Superior click and pop
suppression eliminates audible transients on power-up/down
and during shutdown. Independent left/right shutdown con-
trols maximizes power savings in mixed mono/stereo appli-
cations.
Key Specifications
j
Efficiency at 3.6V, 100mW into 8
80% (typ)
j
Efficiency at 3.6V, 500mW into 8
85% (typ)
j
Efficiency at 5V, 1W into 8
85% (typ)
j
Quiescent Power Supply Current
at 3.6V supply
4mA
j
Power Output at V
DD
= 5V,
R
L
= 4
, THD 10%
2.5W (typ)
j
Power Output at V
DD
= 5V,
R
L
= 8
, THD 10%
1.5W (typ)
j
Shutdown current
0.1A (typ)
Features
n
Output Short Circuit Protection
n
Stereo Class D operation
n
No output filter required
n
Logic selectable gain
n
Independent shutdown control
n
Minimum external components
n
Click and Pop suppression
n
Micro-power shutdown
n
Available in space-saving 2mm x 2mm x 0.6mm micro
SMD package
Applications
n
Mobile phones
n
PDAs
n
Laptops
Boomer
is a registered trademark of National Semiconductor Corporation.
December 2005
LM4674
Filterless
2.5W
Stereo
Class
D
Audio
Power
Amplifier
2005 National Semiconductor Corporation
DS201674
www.national.com
Typical Application
20167402
* Bypass output should be left floating for proper operation in most applications. See Application Information for details.
FIGURE 1. Typical Audio Amplifier Application Circuit
LM4674
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2
Connection Diagrams
TL Package (2mmx2mmx0.6mm)
20167401
Top View
Order Number LM4674TL
See NS Package Number TL1611A
LM4674TL Markings
20167425
Top View
XY = 2 digit datecode
TT = Die traceability
G = Boomer Family
G2 = LM4674TL
LM4674
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3
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 (Note 1)
6.0V
Storage Temperature
-65C to +150C
Input Voltage
0.3V to V
DD
+0.3V
Power Dissipation (Note 3)
Internally Limited
ESD Susceptibility, all other pins (Note 4)
2000V
ESD Susceptibility (Note 5)
200V
Junction Temperature (T
JMAX
)
150C
Thermal Resistance
JA
45.7C/W
Operating Ratings
(Note 1) (Note 2)
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.4V
V
DD
5.5V
Electrical Characteristics V
DD
= 3.6V
(Notes 1, 2)
The following specifications apply for A
V
= 6dB, R
L
= 15H + 8
+ 15H, f = 1kHz unless otherwise specified. Limits apply
for T
A
= 25C.
Symbol
Parameter
Conditions
LM4674
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
V
OS
Differential Output Offset Voltage
V
IN
= 0, V
DD
= 2.4V to 5.0V
5
mV
I
DD
Quiescent Power Supply Current
V
IN
= 0, R
L
=
,
Both channels active, V
DD
= 3.6V
4
6
mA
V
IN
= 0, R
L
=
,
Both channels active, V
DD
= 5V
5
7.5
I
SD
Shutdown Current
V
SD1
= V
SD2
= GND
0.03
1
A
V
SDIH
Shutdown Voltage Input High
1.4
V (min)
V
SDIL
Shutdown Voltage Input Low
0.4
V (max)
T
WU
Wake Up Time
V
SHUTDOWN
= 0.4V
0.5
ms
A
V
Gain
GAIN0, GAIN1 = GND
6
6
0.5
dB
GAIN0 = V
DD
, GAIN1 = GND
12
12
0.5
GAIN0 = GND, GAIN1 = V
DD
18
18
0.5
GAIN0, GAIN1 = V
DD
24
24
0.5
R
IN
Input Resistance
A
V
= 6dB
28
k
A
V
= 12dB
18.75
A
V
= 18dB
11.25
A
V
= 24dB
6.25
LM4674
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Electrical Characteristics V
DD
= 3.6V
(Notes 1, 2)
The following specifications apply for A
V
= 6dB, R
L
= 15H + 8
+ 15H, f = 1kHz unless otherwise specified. Limits apply for
T
A
= 25C. (Continued)
Symbol
Parameter
Conditions
LM4674
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
P
O
Output Power
R
L
= 15H + 4
+ 15H, THD = 10%
f = 1kHz, 22kHz BW
V
DD
= 5V
2.5
W
V
DD
= 3.6V
1.2
V
DD
= 2.5V
0.530
R
L
= 15H + 8
+ 15H, THD = 10%
f = 1kHz, 22kHz BW
V
DD
= 5V
1.5
W
V
DD
= 3.6V
0.78
0.6
V
DD
= 2.5V
0.350
R
L
= 15H + 4
+ 15H, THD = 1%
f = 1kHz, 22kHz BW
V
DD
= 5V
1.9
W
V
DD
= 3.6V
1
V
DD
= 2.5V
0.430
R
L
= 15H + 8
+ 15H, THD = 1%
f = 1kHz, 22kHz BW
V
DD
= 5V
1.25
W
V
DD
= 3.6V
0.63
V
DD
= 2.5V
0.285
THD+N
Total Harmonic Distortion
P
O
= 500mW, f = 1kHz, RL = 8
0.07
%
P
O
= 300mW, f = 1kHz, RL = 8
0.05
PSRR
Power Supply Rejection Ratio
V
RIPPLE
= 200mV
P-P
Sine,
f
Ripple
= 217Hz, Inputs AC GND, C
I
= 1F, input referred
75
dB
V
RIPPLE
= 1V
P-P
Sine,
f
Ripple
= 1kHz, Inputs AC GND, C
I
=
1F, input referred
75
CMRR
Common Mode Rejection Ratio
V
RIPPLE
= 1V
P-P
f
RIPPLE
= 217Hz
67
dB
Efficiency
P
O
= 1W, f = 1kHz,
R
L
= 8
, V
DD
= 5V
85
%
Crosstalk
P
O
= 500mW, f = 1kHz
84
dB
SNR
Signal to Noise Ratio
V
DD
= 5V, P
O
= 1W
96
dB
e
OS
Output Noise
Input referred, A-Weighted Filter
20
V
Note 1: All voltages are measured with respect to the ground pin, 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 derated at elevated temperatures and is dictated by T
JMAX
,
JA
, and the ambient temperature, T
A
. The maximum
allowable power dissipation is P
DMAX
= (T
JMAX
T
A
)/
JA
or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4674 see power derating
currents for more information.
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Machine Model, 220pF240pF discharged through all pins.
Note 6: Typicals are measured at 25C and represent the parametric norm.
Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
LM4674
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