LM4666
Filterless High Efficiency Stereo 1.2W Switching Audio
Amplifier
General Description
The LM4666 is a fully integrated single-supply high efficiency
switching audio amplifier. It features an innovative modulator
that eliminates the LC output filter used with typical switching
amplifiers. Eliminating the output filter reduces parts count,
simplifies circuit design, and reduces board area. The
LM4666 processes analog inputs with a delta-sigma modu-
lation technique that lowers output noise and THD when
compared to conventional pulse width modulators.
The LM4666 is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing on a single 3V supply, it is capable of driving 8
trans-
ducer loads at a continuous average output of 450mW with
less than 1%THD+N. Its flexible power supply requirements
allow operation from 2.8V to 5.5V.
The LM4666 has high efficiency with an 8
transducer load
compared to a typical Class AB amplifier. With a 3V supply,
the IC's efficiency for a 100mW power level is 79%, reaching
84% at 450mW output power.
The LM4666 features a low-power consumption shutdown
mode. Shutdown may be enabled by driving the Shutdown
pin to a logic low (GND).
The LM4666 has fixed selectable gain of either 6dB or 12dB.
The LM4666 has short circuit protection against a short from
the outputs to V
DD
or GND.
Key Specifications
j
Efficiency at 3V, 100mW into 8
transducer 79% (typ)
j
Efficiency at 3V, 450mW into 8
transducer 84% (typ)
j
Efficiency at 5V, 1W into 8
transducer
85% (typ)
j
Total quiescent power supply current
7.0mA (typ)
j
Total shutdown power supply current
0.02A (typ)
j
Single supply range
2.8V to 5.5V
Features
n
No output filter required for inductive transducers
n
Selectable gain of 6dB or 12dB
n
Very fast turn on time: 6ms (typ)
n
Minimum external components
n
"Click and pop" suppression circuitry
n
Micro-power shutdown mode
n
Short circuit protection
n
Available in space-saving SDA package
Applications
n
Mobile phones
n
PDAs
n
Portable electronic devices
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
200558E6
FIGURE 1. Typical Audio Amplifier Application Circuit
May 2004
LM4666
Filterless
High
Efficiency
Stereo
1.2W
Switching
Audio
Amplifier
2004 National Semiconductor Corporation
DS200558
www.national.com
Connection Diagrams
SDA Package
200558I8
Top View
Order Number LM4666SDA
See NS Package Number SDA14A
SDA Marking
200558I9
Top View
Z -- Plant Code
XY -- Date Code
TT -- Die Traceability
L4666 -- LM4666
LM4666
www.national.com
2
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 (Note1)
6.0V
Storage Temperature
-65C to +150C
Voltage at Any Input Pin
V
DD
+ 0.3V
V GND - 0.3V
Power Dissipation (Note 3)
Internally Limited
ESD Susceptibility,
pins 4, 7, 11, 14 (Note 4)
1kV
ESD Susceptibility,
all other pins (Note 4)
2.0kV
ESD Susceptibility (Note 5)
200V
Junction Temperature (T
J
)
150C
Thermal Resistance
JA
(SDA)
63C/W
JC
(SDA)
12C/W
Soldering Information
See AN-1112 "microSMD Wafers Level Chip Scale
Package."
Operating Ratings
(Notes 1, 2)
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.8V
V
DD
5.5V
Electrical Characteristics V
DD
= 5V
(Notes 1, 2)
The following specifications apply for V
DD
= 5V and R
L
= 15H + 8
+ 15H unless otherwise specified. Limits apply for T
A
=
25C.
Symbol
Parameter
Conditions
LM4666
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, No Load
V
IN
= 0V, R
L
= 15H + 8
+ 15H
15
16
mA
mA
I
SD
Shutdown Current
V
SD
= GND (Note 9)
0.02
A
V
SDIH
Shutdown Voltage Input High
1.2
V
V
SDIL
Shutdown Voltage Input Low
1.1
V
V
GSIH
Gain Select Input High
1.2
V
V
GSIL
Gain Select Input Low
1.1
V
A
V
Closed Loop Gain
V
Gain Select
= V
DD
6
dB
A
V
Closed Loop Gain
V
Gain Select
= GND
12
dB
V
OS
Output Offset Voltage
10
mV
T
WU
Wake-up Time
6
ms
P
o
Output Power
THD = 1% (max), f = 1kHz,
22kHz BW
1.2
W
THD+N
Total Harmonic Distortion+Noise
P
O
= 100mW
RMS
/Channel,
f
IN
= 1kHz, 22kHz BW,
Both channels in phase
0.65
%
X
TALK
Channel Separation
P
O
= 100mW
RMS
, f = 1kHz
57
dB
R
IN
Differential Input Resistance
V
Gain Select
= V
DD
90
k
V
Gain Select
= GND
60
k
PSRR
Power Supply Rejection Ratio
V
Ripple
= 100mV
RMS
sine wave,
f
RIPPLE
= 217Hz
Inputs terminated to AC GND
60
dB
V
Ripple
= 100mV
RMS
sine wave,
f
RIPPLE
= 217Hz
P
OUT
= 10mW,1kHz
65
dB
CMRR
Common Mode Rejection Ratio
V
Ripple
= 100mV
RMS
,
f
Ripple
= 217Hz, Input referred
48
dB
SNR
Signal to Noise Ratio
P
O
= 1W
RMS
; A-Weighted Filter
83
dB
e
OUT
Output Noise
A-Weighted filter, V
in
= 0V
200
V
LM4666
www.national.com
3
Electrical Characteristics V
DD
= 3V
(Notes 1, 2)
The following specifications apply for V
DD
= 3V and R
L
= 15H + 8
+ 15H unless otherwise specified. Limits apply for T
A
=
25C.
Symbol
Parameter
Conditions
LM4666
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, No Load
V
IN
= 0V, R
L
= 15H + 8
+ 15H
6.5
7.0
10
mA (max)
I
SD
Shutdown Current
V
SD
= GND (Note 9)
0.02
2.0
A (max)
V
SDIH
Shutdown Voltage Input High
1.0
1.4
V (min)
V
SDIL
Shutdown Voltage Input Low
0.8
0.4
V (max)
V
GSIH
Gain Select Input High
1.0
1.4
V (min)
V
GSIL
Gain Select Input Low
0.8
0.4
V (max)
A
V
Closed Loop Gain
V
Gain Select
= V
DD
6
5.25
6.75
dB (min)
dB (max)
A
V
Closed Loop Gain
V
Gain Select
= GND
12
11.25
12.75
dB (min)
dB (max)
V
OS
Output Offset Voltage
10
35
mV (max)
T
WU
Wake-up Time
6
ms
P
o
Output Power
THD = 1% (max); f = 1kHz,
22kHz BW
450
400
mW (min)
THD+N
Total Harmonic Distortion+Noise
P
O
= 100mW
RMS
/Channel,
f
IN
= 1kHz, 22kHz BW,
Both channels in phase
0.65
%
X
TALK
Channel Separation
P
O
= 100mW
RMS
, f = 1kHz
57
dB
R
IN
Differential Input Resistance
V
Gain Select
= V
DD
90
k
V
Gain Select
= GND
60
k
PSRR
Power Supply Rejection Ratio
V
ripple
= 100mV
RMS
sine wave,
f
RIPPLE
= 217Hz,
Inputs terminated to AC GND
60
dB
V
Ripple
= 100mV
RMS
sine wave,
f
RIPPLE
= 217Hz,
P
OUT
= 10mW,1kHz
65
dB
CMRR
Common Mode Rejection Ratio
V
Ripple
= 100mV
RMS
,
f
Ripple
= 217Hz, Input referred
48
dB
SNR
Signal to Noise Ratio
P
O
= 400mW
RMS
, A-Weighted Filter
83
dB
e
OUT
Output Noise
A-Weighted filter, V
in
= 0V
125
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 LM4666, T
JMAX
= 150C.
The typical
JA
is 63C/W and the typical
JC
is 12C/W for the SDA package.
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Machine Model, 220pF 240pF discharged through all pins.
Note 6: Typical specifications are specified 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: Shutdown current is measured in a normal room environment. Exposure to direct sunlight will increase I
SD
by a maximum of 2A. The Shutdown pin should
be driven as close as possible to GND for minimal shutdown current and to V
DD
for the best THD performance in PLAY mode. See the Application Information
section under SHUTDOWN FUNCTION for more information.
Note 10: The performance graphs were taken using the Audio Precision AUX0025 Switching Amplifier Measurement Filter in series with the LC filter on the demo
board.
LM4666
www.national.com
4
External Components Description
(Figure 1)
Components
Functional Description
1.
C
S
Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply Bypassing
section for information concerning proper placement and selection of the supply bypass capacitor.
2.
C
I
Input AC coupling capacitor which blocks the DC voltage at the amplifier's input terminals.
Typical Performance Characteristics
(Note 10)
THD+N vs Frequency
V
DD
= 5V, R
L
= 15H + 8
+ 15H
P
OUT
= 100mW/Channel, 30kHz BW
THD+N vs Frequency
V
DD
= 3V, R
L
= 15H + 8
+ 15H
P
OUT
= 100mW/Channel, 30kHz BW
20055827
20055826
THD+N vs Frequency
V
DD
= 3V, R
L
= 15H + 4
+ 15H
P
OUT
= 100mW/Channel, 30kHz BW
THD+N vs Output Power/Channel
V
DD
= 5V, R
L
= 15H + 8
+ 15H
f = 1kHz, 22kHz BW
20055825
20055830
LM4666
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