National Semiconductor LM4940 Technical data
LM4940
6W Stereo Audio Power Amplifier
LM4940 6W Stereo Audio Power Amplifier
October 2003
General Description
The LM4940 is a dual audio power amplifier primarily designed for demanding applications in flat panel monitors and
TV’s. It is capable of delivering 6 watts per channel to a 4Ω
load with less than 10% THD+N while operating on a
14.4V
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4940 does not require bootstrap capacitors or snubber circuits. Therefore, it is ideally
suited for display applications requiring high power and minimal size.
The LM4940 features a low-power consumption active-low
shutdown mode. Additionally, the LM4940 features an internal thermal shutdown protection mechanism along with short
circuit protection.
The LM4940 contains advanced pop & click circuitry that
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4940 is a unity-gain stable and can be configured by
external gain-setting resistors.
power supply.
DC
Typical Application
Key Specifications
j
Quiscent Power Supply Current 40mA (max)
j
P
(SE)
OUT
V
= 14.4V, RL=4Ω, 10% THD+N 6W (typ)
DD
j
Shutdown current 40µA (typ)
Features
n Pop & click circuitry eliminates noise during turn-on and
turn-off transitions
n Low current, active-low shutdown mode
n Low quiescent current
n Stereo 6W output, R
n Short circuit protection
n Unity-gain stable
n External gain configuration capability
L
=4Ω
Applications
n Flat Panel Monitors
n Flat Panel TV’s
n Computer Sound Cards
20075672
FIGURE 1. Typical Stereo Audio Amplifier Application Circuit
Boomer®is a registered trademark of National Semiconductor Corporation.
© 2003 National Semiconductor Corporation DS200756 www.national.com
Connection Diagram
LM4940
Plastic Package, TO-263
Top View
U = Wafer Fab Code
Z = Assembly Plant Code
XY = Date Code
TT = Die Traceability
Order Number LM4940TS
See NS Package Number TS9A
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LM4940
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 (pin 6, referenced
to GND, pins 4 and 5) 18.0V
ESD Susceptibility (Note 5) 200V
Junction Temperature 150˚C
Thermal Resistance
θ
(TS) 4˚C/W
JC
θ
(TS) (Note 3) 20˚C/W
JA
θ
(TA) 4˚C/W
JC
θ
(TA) (Note 3) 20˚C/W
JA
Storage Temperature −65˚C to +150˚C
Input Voltage
pins 3 and 7 −0.3V to V
DD
+ 0.3V
pins 1, 2, 8, and 9 −0.3V to 9.5V
Power Dissipation (Note 3) Internally limited
ESD Susceptibility (Note 4) 2000V
Operating Ratings
Temperature Range
T
≤ TA≤ T
MIN
MAX
Supply Voltage 10V ≤ V
−40˚C ≤ TA≤ 85˚C
DD
≤ 16V
Electrical Characteristics VDD= 12V (Notes 1, 2)
The following specifications apply for VDD= 12V, AV= 10, RL=4Ω, f = 1kHz unless otherwise specified. Limits apply for TA=
25˚C.
Symbol Parameter Conditions LM4940 Units
Typical
(Note 6)
I
DD
I
SD
V
SDIH
V
SDIL
Quiescent Power Supply Current VIN= 0V, IO= 0A, No Load 16 40 mA (max)
Shutdown Current V
SHUTDOWN
= GND (Note 9) 40 100 µA (max)
Shutdown Voltage Input High 2.0
Shutdown Voltage Input Low 0.4 V (max)
Limit
(Notes 7, 8)
V
DD
Single Channel
P
O
Output Power
THD+N Total Harmomic Distortion + Noise P
e
OS
X
TALK
Output Noise A-Weighted Filter, VIN= 0V,
Channel Separation PO=1W 70 dB
PSRR Power Supply Rejection Ratio V
Note 1: All voltages are measured with respect to the GND 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 andAC 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
allowable power dissipation is P
in Figure 1) with V
heatsink surface area.
Note 4: Human body model, 100pF discharged through a 1.5 kΩ resistor.
Note 5: Machine Model, 220pF– 240pF discharged through all pins.
Note 6: Typicals are measured at 25˚C and represent the parametric norm.
Note 7: 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. The Shutdown pin should be driven as close as possible to GND for minimum shutdown
current.
= 12V, RL=4Ω stereo operation the total power dissipation is 3.65W. θJA= 20˚C/W for both TO263 and TO220 packages mounted to 16in
DD
DMAX
=(T
)/θJAor the given inAbsolute Maximum Ratings, whichever is lower. For the LM4940 typical application (shown
JMAX−TA
THD+N = 1% 3.1 2.8
THD+N = 10% 4.2
V
= 14.4V, THD+N = 10% 6.0
DD
= 1Wrms, AV= 10, f = 1kHz 0.15 %
O
Input Referred
= 200mV
RIPPLE
1kHz
p-p,fRIPPLE
=
, θJA, and the ambient temperature, TA. The maximum
JMAX
10 µV
56 dB
(Limits)
V (min)
/2
V (max)
W (min)
2
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Typical Application
LM4940
FIGURE 2. Typical Stereo Audio Amplifier Application Circuit
External Components Description Refer to (Figure 1.)
Components Functional Description
This is the inverting input resistance that, along with RF, sets the closed-loop gain. Input
1. R
2. C
3. R
4. C
5. C
BYPASS
6. C
resistance R
IN
=1/(2πRINCIN).
This is the input coupling capacitor. It blocks DC voltage at the amplifier’s inverting input. CINand
IN
IN
create a highpass filter. The filter’s cutoff frequency is fC=1/(2πRINCIN). Refer to the
R
SELECTING EXTERNAL COMPONENTS section for an explanation of determining C
This is the feedback resistance that, along with Ri, sets closed-loop gain.
F
The supply bypass capacitor. Refer to the POWER SUPPLY BYPASSING section for information
S
about properly placing, and selecting the value of, this capacitor.
This capacitor filters the half-supply voltage present on the BYPASS pin. Refer to the Application
section, SELECTING EXTERNAL COMPONENTS, for information about properly placing, and
selecting the value of, this capacitor.
This is the output coupling capacitor. It blocks the nominal VDD/2 voltage present at the output
OUT
and prevents it from reaching the load. C
frequency is f
for an explanation of determining C
and input capacitance CINform a high pass filter. The filter’s cutoff frequency is f
IN
and RLform a high pass filter whose cutoff
OUT
=1/(2πRLC
C
). Refer to the SELECTING EXTERNAL COMPONENTS section
OUT
’s value.
OUT
20075672
’s value.
IN
C
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Typical Performance Characteristics
THD+N vs Frequency THD+N vs Frequency
LM4940
VDD= 12V, RL=4Ω, SE operation,
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both channels driven and loaded (average shown),
= 1W, AV=1
P
OUT
THD+N vs Frequency THD+N vs Output Power
VDD= 12V, RL=8Ω, SE operation,
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both channels driven and loaded (average shown),
= 1W, AV=1
P
OUT
THD+N vs Output Power THD+N vs Output Power
VDD= 12V, RL=4Ω, SE operation,
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both channels driven and loaded (average shown),
= 2.5W, AV=1
P
OUT
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VDD= 14.4V, RL=4Ω, SE operation, AV=1
single channel driven/single channel measured,
= 1kHz
f
IN
VDD= 12V, RL=4Ω, SE operation, AV=1
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single channel driven/single channel measured,
= 1kHz
f
IN
VDD= 12V, RL=8Ω, SE operation, AV=1
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single channel driven/single channel measured,
= 1kHz
f
IN
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