LM4894
1 Watt Fully Differential Audio Power Amplifier With
Shutdown Select
General Description
The LM4894 is a fully differential audio power amplifier
primarily designed for demanding applications in mobile
phones and other portable communication device applica-
tions. It is capable of delivering 1 watt of continuous average
power to an 8
BTL load with less than 1% distortion
(THD+N) from a 5V
DC
power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4894 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for mobile phone and other low voltage appli-
cations where minimal power consumption is a primary re-
quirement.
The LM4894 features a low-power consumption shutdown
mode. To facilitate this, Shutdown may be enabled by either
logic high or low depending on mode selection. Driving the
shutdown mode pin either high or low enables the shutdown
select pin to be driven in a likewise manner to enable Shut-
down. Additionally, the LM4894 features an internal thermal
shutdown protection mechanism.
The LM4894 contains advanced pop & click circuitry which
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4894 is unity-gain stable and can be configured by
external gain-setting resistors.
Key Specifications
j
Improved PSRR at 217Hz
80dB(typ)
j
Power Output at 5.0V & 1% THD
1.0W(typ)
j
Power Output at 3.3V & 1% THD
400mW(typ)
j
Shutdown Current
0.1A(typ)
Features
n
Fully differential amplification
n
Available in space-saving packages micro SMD, MSOP,
and LLP
n
Ultra low current shutdown mode
n
Can drive capacitive loads up to 500pF
n
Improved pop & click circuitry eliminates noises during
turn-on and turn-off transitions
n
2.2 - 5.5V operation
n
No output coupling capacitors, snubber networks or
bootstrap capacitors required
n
Unity-gain stable
n
External gain configuration capability
n
Shutdown high or low selectivity
n
High CMRR
Applications
n
Mobile phones
n
PDAs
n
Portable electronic devices
Connection Diagrams
Mini Small Outline (MSOP) Package
LLP Package
20013723
Top View
Order Number LM4894MM
See NS Package Number MUB10A
20013735
Top View
Order Number LM4894LD
See NS Package Number LDA10B
Boomer
is a registered trademark of National Semiconductor Corporation.
June 2003
LM4894
1
W
att
Fully
Differential
Audio
Power
Amplifier
W
ith
Shutdown
Select
2003 National Semiconductor Corporation
DS200137
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Connection Diagrams
(Continued)
9 Bump micro SMD Package
9 Bump micro SMD Package
20013736
Top View
Order Number LM4894IBP
See NS Package Number BPA09CDB
20013794
Top View
Order Number LM4894ITL, LM4894ITLX
See NS Package Number TLA09AAA
Typical Application
20013701
FIGURE 1. Typical Audio Amplifier Application Circuit
LM4894
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2
Absolute Maximum Ratings
(Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
6.0V
Storage Temperature
-65C to +150C
Input Voltage
-0.3V to V
DD
+0.3V
Power Dissipation (Note 3)
Internally Limited
ESD Susceptibility (Note 4)
2000V
ESD Susceptibility (Note 5)
200V
Junction Temperature
150C
Thermal Resistance
JC
(LLP)
12C/W
JA
(LLP)
63C/W
JA
(micro SMD)
220C/W
JC
(MSOP)
56C/W
JA
(MSOP)
190C/W
Soldering Information
See AN-1112 "microSMD Wafers Level Chip Scale
Package."
See AN-1187 "Leadless
Leadframe Package (LLP)."
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.2V
V
DD
5.5V
Electrical Characteristics V
DD
= 5V
(Notes 1, 2, 8)
The following specifications apply for V
DD
= 5V, A
V
= 1, and 8
load unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4894
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A
4
8
mA (max)
I
SD
Shutdown Current
V
shutdown
= GND
0.1
1
A (max)
P
o
Output Power
THD = 1% (max); f = 1 kHz
LM4894LD, R
L
= 4
(Note 11)
1.4
W (min)
LM4894, R
L
= 8
1
0.850
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.4 Wrms; f = 1kHz
0.1
%
PSRR
Power Supply Rejection Ratio
V
ripple
= 200mV sine p-p
f = 217Hz (Note 9)
87
dB (min)
f = 1kHz (Note 9)
83
f = 217Hz (Note 10)
83
63
f = 1kHz (Note 10)
80
CMRR
Common_Mode Rejection Ratio
f = 217Hz
50
dB
Electrical Characteristics V
DD
= 3V
(Notes 1, 2, 8)
The following specifications apply for V
DD
= 3V, A
V
= 1, and 8
load unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4894
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
I
DD
Quiescent Power Supply Current
V
IN
= 0V, I
o
= 0A
3.5
6
mA (max)
I
SD
Shutdown Current
V
shutdown
= GND
0.1
1
A (max)
P
o
Output Power
THD = 1% (max); f = 1kHz
0.35
W
THD+N
Total Harmonic Distortion+Noise
P
o
= 0.25Wrms; f = 1kHz
0.325
%
PSRR
Power Supply Rejection Ratio
V
ripple
= 200mV sine p-p
f = 217Hz (Note 9)
87
dB
f = 1kHz (Note 9)
83
f = 217Hz (Note 10)
80
f = 1kHz (Note 10)
78
CMRR
Common-Mode Rejection Ratio
f = 217Hz
49
dB
LM4894
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Electrical Characteristics V
DD
= 3V
(Notes 1, 2, 8)
The following specifications apply for V
DD
= 3V, A
V
= 1, and 8
load unless otherwise specified. Limits apply for T
A
=
25C. (Continued)
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 LM4894, see power derating
currents for additional 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: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 8: For micro SMD only, shutdown current is measured in a Normal Room Environment. Exposure to direct sunlight will increase I
SD
by a maximum of 2A.
Note 9: Unterminated input.
Note 10: 10
terminated input.
Note 11: When driving 4
loads from a 5V supply, the LM4894LD must be mounted to a circuit board.
External Components Description
(Figure 1)
Components
Functional Description
1.
R
i
Inverting input resistance which sets the closed-loop gain in conjunction with R
f
.
2.
R
f
Feedback resistance which sets the closed-loop gain in conjunction with R
i
.
3.
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.
4.
C
B
Bypass pin capacitor which provides half-supply filtering. Refer to the section, Proper Selection of External
Components, for information concerning proper placement and selection of C
B
.
LM4894
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Typical Performance Characteristics
LD Specific Characteristics
LM4894LD
THD+N vs Output Power
V
DD
= 5V, 4
R
L
LM4894LD
THD+N vs Frequency
V
DD
= 5V, 4
R
L
, and Power = 1W
20013790
20013791
LM4894LD
Power Dissipation vs
Output Power
LM4894LD
Power Derating Curve
20013792
20013793
LM4894
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