LM4951
Wide Voltage Range 1.8 Watt Audio Amplifier
General Description
Key Specifications
The LM4951 is an audio power amplifier primarily designed
for demanding applications in Portable Handheld devices. It
is capable of delivering 1.8W mono BTL to an 8Ω load,
continuous average power, with less than 1% distortion
(THD+N) from a 7.5VDC power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4951 does not require bootstrap capacitors, or snubber circuits.
The LM4951 features a low-power consumption active-low
shutdown mode. Additionally, the LM4951 features an internal thermal shutdown protection mechanism.
The LM4951 contains advanced pop & click circuitry that
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4951 is unity-gain stable and can be configured by
external gain-setting resistors.
j Wide Voltage Range
2.7V to 9V
j Quiescent Power Supply Current
(VDD = 7.5V)
2.5mA (typ)
j Power Output BTL at 7.5V,
1% THD
1.8W (typ)
j Shutdown Current
0.01µA (typ)
j Fast Turn on Time
25mS (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 Thermal shutdown protection
n Unity-gain stable
n External gain configuration capability
Applications
n Portable Handheld Devices up to 9V
n Cell Phone
n PDA
Typical Application
200942F4
* RC is needed for over/under voltage protection. If inputs are less than VDD +0.3V and greater than –0.3V, and if inputs are
disabled when in shutdown mode, then RC may be shorted.
FIGURE 1. Typical Bridge-Tied-Load (BTL) Audio Amplifier Application Circuit
Boomer ® is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation
DS200942
www.national.com
LM4951 Wide Voltage Range 1.8 Watt Audio Amplifier
November 2005
LM4951
Connection Diagrams
SD Package
20094229
Top View
Order Number LM4951SD
See NS Package Number SDC10A
9 Bump micro SMD Package
20094228
Top View
Order Number LM4951TL, TLX
See NS Package Number TLA09ZZA
* DAP can either be soldered to GND or left floating.
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2
Thermal Resistance
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
See AN-1187 ’Leadless
Leadframe Packaging (LLP).’
Supply Voltage
θJA (LLP) (Note 3)
73˚C/W
9.5V
Storage Temperature
−65˚C to +150˚C
Operating Ratings
−0.3V to VDD + 0.3V
Input Voltage
Power Dissipation (Note 3)
Internally limited
ESD Susceptibility (Note 4)
2000V
ESD Susceptibility (Note 5)
Temperature Range
TMIN ≤ TA ≤ TMAX
200V
Junction Temperature
−40˚C ≤ T
A
≤ +85˚C
2.7V ≤ VDD ≤ 9V
Supply Voltage
150˚C
Electrical Characteristics VDD = 7.5V (Notes 1, 2)
The following specifications apply for VDD = 7.5V, AV-BTL = 6dB, RL = 8Ω unless otherwise specified. Limits apply for TA =
25˚C.
Symbol
Parameter
Conditions
LM4951
Typical
(Note 6)
Limit
(Notes 7, 8)
Units
(Limits)
IDD
Quiescent Power Supply Current
VIN = 0V, IO = 0A,RL = 8Ω
2.5
4.5
mA (max)
ISD
Shutdown Current
VSHUTDOWN = GND (Note 9)
0.01
5
µA (max)
VOS
Offset Voltage
30
mV (max)
VSDIH
Shutdown Voltage Input High
1.2
V (min)
VSDIL
Shutdown Voltage Input Low
0.4
V (max)
Rpulldown
Pulldown Resistor on S/D
45
kΩ (min)
TWU
Wake-up Time
CB = 1.0µF
Tsd
Shutdown time
CB = 1.0µF
10
ms (max)
TSD
Thermal Shutdown Temperature
170
150
190
˚C (min)
˚C (max)
PO
Output Power
THD = 1% (max); f = 1kHz
RL = 8Ω Mono BTL
1.8
1.5
W (min)
THD+N
Total Harmomic Distortion + Noise
PO = 600mWrms; f = 1kHz
AV-BTL = 6dB
0.07
0.5
% (max)
THD+N
Total Harmomic Distortion + Noise
PO = 600mWrms; f = 1kHz
AV-BTL = 26dB
0.35
%
eOS
Output Noise
A-Weighted Filter, Ri = Rf = 20kΩ
Input Referred, Note 10
10
µV
PSRR
Power Supply Rejection Ratio
VRIPPLE = 200mVp-p, f = 217Hz,
CB = 1.0µF, Input Referred
66
5
75
25
ms
56
dB (min)
Electrical Characteristics VDD = 3.3V (Notes 1, 2)
The following specifications apply for VDD = 3.3V, AV-BTL = 6dB, RL = 8Ω unless otherwise specified. Limits apply for TA =
25˚C.
Symbol
Parameter
Conditions
LM4951
Typical
(Note 6)
Limit
(Notes 7, 8)
Units
(Limits)
IDD
Quiescent Power Supply Current
VIN = 0V, IO = 0A,RL = 8Ω
2.5
4.5
mA (max)
ISD
Shutdown Current
VSHUTDOWN = GND (Note 9)
0.01
2
µA (max)
VOS
Offset Voltage
30
mV (max)
VSDIH
Shutdown Voltage Input High
1.2
V (min)
VSDIL
Shutdown Voltage Input Low
0.4
V (max)
TWU
Wake-up Time
CB = 1.0µF
Tsd
Shutdown time
CB = 1.0µF
3
3
25
ms (max)
10
ms (max)
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LM4951
Absolute Maximum Ratings (Notes 1, 2)
LM4951
Electrical Characteristics VDD = 3.3V (Notes 1, 2)
(Continued)
The following specifications apply for VDD = 3.3V, AV-BTL = 6dB, RL = 8Ω unless otherwise specified. Limits apply for TA =
25˚C.
Symbol
Parameter
Conditions
LM4951
Typical
(Note 6)
Limit
(Notes 7, 8)
Units
(Limits)
PO
Output Power
THD = 1% (max); f = 1kHz
RL = 8Ω Mono BTL
280
230
W (min)
THD+N
Total Harmomic Distortion + Noise1 PO = 100mWrms; f = 1kHz
AV-BTL = 6dB
0.07
0.5
% (max)
THD+N
Total Harmomic Distortion + Noise1 PO = 100mWrms; f = 1kHz
AV-BTL = 26dB
0.35
%
eOS
Output Noise
A-Weighted Filter, Ri = Rf = 20kΩ
Input Referred, Note 10
10
µV
PSRR
Power Supply Rejection Ratio
VRIPPLE = 200mVp-p, f = 217Hz,
CB = 1µF, Input Referred
71
61
dB (min)
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 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 TJMAX, θJA, and the ambient temperature, TA. The maximum
allowable power dissipation is P DMAX = (TJMAX − TA) / θJA or the given in Absolute Maximum Ratings, whichever is lower. For the LM4951 typical application (shown
in Figure 1) with VDD = 7.5V, RL = 8Ω mono-BTL operation the max power dissipation is 1.42W. θJA = 73˚C/W.
Note 4: Human body model, 100pF discharged through a 1.5kΩ 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.
Note 10: Noise measurements are dependent on the absolute values of the closed loop gain setting resistors (input and feedback resistors).
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4
LM4951
Typical Performance Characteristics
THD+N vs Frequency
VDD = 3.3V, PO = 100mW, AV = 26dB
THD+N vs Frequency
VDD = 3.3V, PO = 100mW, AV = 6dB
200942F9
20094202
THD+N vs Frequency
VDD = 5V, PO = 400mW, AV = 26dB
THD+N vs Frequency
VDD = 5V, PO = 400mW, AV = 6dB
20094203
20094204
THD+N vs Frequency
VDD = 7.5V, PO = 600mW, AV = 26dB
THD+N vs Frequency
VDD = 7.5V, PO = 600mW, AV = 6dB
20094205
200942G0
5
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LM4951
Typical Performance Characteristics
(Continued)
THD+N vs Output Power
VDD = 3.3V, f = 1kHz, AV = 6dB
THD+N vs Output Power
VDD = 3.3V, f = 1kHz, AV = 26dB
200942G1
20094208
THD+N vs Output Power
VDD = 5V, f = 1kHz, AV = 26dB
THD+N vs Output Power
VDD = 5V, f = 1kHz, AV = 6dB
20094209
20094210
THD+N vs Output Power
VDD = 7.5V, f = 1kHz, AV = 26dB
THD+N vs Output Power
VDD = 7.5V, f = 1kHz, AV = 6dB
20094212
20094211
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6
(Continued)
Power Supply Rejection vs Frequency
VDD = 3.3V, AV = 26dB, VRIPPLE = 200mVP-P
Input Terminated into 10Ω
Power Supply Rejection vs Frequency
VDD = 3.3V, AV = 6dB, VRIPPLE = 200mVP-P
Input Terminated into 10Ω
20094214
20094213
Power Supply Rejection vs Frequency
VDD = 5V, AV = 26dB, VRIPPLE = 200mVP-P
Input Terminated into 10Ω
Power Supply Rejection vs Frequency
VDD = 5V, AV = 6dB, VRIPPLE = 200mVP-P
Input Terminated into 10Ω
20094216
20094215
Power Supply Rejection vs Frequency
VDD = 7.5V, AV = 26dB, VRIPPLE = 200mVP-P
Input Terminated into 10Ω
Power Supply Rejection vs Frequency
VDD = 7.5V, AV = 6dB, VRIPPLE = 200mVP-P
Input Terminated into 10Ω
20094218
20094217
7
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LM4951
Typical Performance Characteristics
LM4951
Typical Performance Characteristics
(Continued)
Noise Floor
VDD = 3V, AV = 26dB, Ri = 20kΩ, Rf = 200kΩ
BW < 80kHz, A-weighted
Noise Floor
VDD = 3.3V, AV = 6dB, Ri = Rf = 20kΩ
BW < 80kHz, A-weighted
20094220
20094219
Noise Floor
VDD = 5V, AV = 26dB, Ri = 20kΩ, Rf = 200kΩ
BW < 80kHz, A-weighted
Noise Floor
VDD = 5V, AV = 6dB, Ri = Rf = 20kΩ
BW < 80kHz, A-weighted
20094222
20094221
Noise Floor
VDD = 7.5V, AV = 26dB, Ri = 20kΩ, Rf = 200kΩ
BW < 80kHz, A-weighted
Noise Floor
VDD = 7.5V, AV = 6dB, Ri = Rf = 20kΩ
BW < 80kHz, A-weighted
20094224
20094223
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VDD
LM4951
Typical Performance Characteristics
(Continued)
Power Dissipation
vs Output Power
= 3.3V, RL = 8Ω, f = 1kHz
VDD
20094225
Power Dissipation
vs Output Power
= 7.5V, RL = 8Ω, f = 1kHz
20094226
Clipping Voltage vs Supply Voltage
RL = 8Ω,
from top to bottom: Negative Voltage Swing; Positive
Voltage Swing
Supply Current
vs Supply Voltage
RL = 8Ω, VIN = 0V, Rsource = 50Ω
20094227
200942E9
Output Power vs Load Resistance
VDD = 3.3V, f = 1kHz
from top to bottom: THD+N = 10%, THD+N = 1%
Output Power vs Supply Voltage
RL = 8Ω,
from top to bottom: THD+N = 10%, THD+N = 1%
200942F1
200942F0
9
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LM4951
Typical Performance Characteristics
(Continued)
Output Power vs Load Resistance
VDD = 7.5V, f = 1kHz
from top to bottom: THD+N = 10%, THD+N = 1%
Frequency Response vs Input Capacitor Size
RL = 8Ω
from top to bottom: Ci = 1.0µF, Ci = 0.39µF, Ci = 0.039µF
200942F2
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200942F3
10
PDMAX’ = (TJMAX - TA) / θJA
(3)
HIGH VOLTAGE BOOMER
Unlike previous 5V Boomer ® amplifiers, the LM4951 is designed to operate over a power supply voltages range of
2.7V to 9V. Operating on a 7.5V power supply, the LM4951
will deliver 1.8W into an 8Ω BTL load with no more than 1%
THD+N.
The LM4951’s TJMAX = 150˚C. In the SD package, the
LM4951’s θJA is 73˚C/W when the metal tab is soldered to a
copper plane of at least 1in2. This plane can be split between
the top and bottom layers of a two-sided PCB. Connect the
two layers together under the tab with an array of vias. At any
given ambient temperature TA, use Equation (3) to find the
maximum internal power dissipation supported by the IC
packaging. Rearranging Equation (3) and substituting PDMAX
for PDMAX’ results in Equation (4). This equation gives the
maximum ambient temperature that still allows maximum
stereo power dissipation without violating the LM4951’s
maximum junction temperature.
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4951 consists of two operational amplifiers that drive a speaker connected between
their outputs. The value of input and feedback resistors
determine the gain of each amplifier. External resistors Ri
and Rf set the closed-loop gain of AMPA, whereas two 20kΩ
internal resistors set AMPB’s gain to -1. The LM4951 drives
a load, such as a speaker, connected between the two
amplifier outputs, VO+ and VO -. Figure 1 shows that AMPA’s
output serves as AMPB’s input. This results in both amplifiers
producing signals identical in magnitude, but 180˚ out of
phase. Taking advantage of this phase difference, a load is
placed between AMPA and AMPB and driven differentially
(commonly referred to as "bridge mode"). This results in a
differential, or BTL, gain of
AVD = 2(Rf / Ri)
TA = TJMAX - PDMAX-MONOBTLθJA
For a typical application with a 7.5V power supply and a BTL
8Ω load, the maximum ambient temperature that allows
maximum stereo power dissipation without exceeding the
maximum junction temperature is approximately 46˚C for the
TS package.
TJMAX = PDMAX-MONOBTLθJA + TA
(1)
The above examples assume that a device is operating
around the maximum power dissipation point. Since internal
power dissipation is a function of output power, higher ambient temperatures are allowed as output power or duty
cycle decreases.
If the result of Equation (2) is greater than that of Equation
(3), then decrease the supply voltage, increase the load
impedance, or reduce the ambient temperature. Further,
ensure that speakers rated at a nominal 8Ω do not fall below
6Ω. If these measures are insufficient, a heat sink can be
added to reduce θJA. The heat sink can be created using
additional copper area around the package, with connections to the ground pins, supply pin and amplifier output pins.
Refer to the Typical Performance Characteristics curves
for power dissipation information at lower output power levels.
POWER SUPPLY VOLTAGE LIMITS
Continuous proper operation is ensured by never exceeding
the voltage applied to any pin, with respect to ground, as
listed in the Absolute Maximum Ratings section.
POWER DISSIPATION
Power dissipation is a major concern when designing a
successful bridged amplifier.
The LM4951’s dissipation when driving a BTL load is given
by Equation (2). For a 7.5V supply and a single 8Ω BTL load,
the dissipation is 1.42W.
2
/ 2π2RL:
(5)
Equation (5) gives the maximum junction temperature
TJMAX. If the result violates the LM4951’s 150˚C, reduce the
maximum junction temperature by reducing the power supply voltage or increasing the load resistance. Further allowance should be made for increased ambient temperatures.
Bridge mode amplifiers are different from single-ended amplifiers that drive loads connected between a single amplifier’s output and ground. For a given supply voltage, bridge
mode has a distinct advantage over the single-ended configuration: its differential output doubles the voltage swing
across the load. Theoretically, this produces four times the
output power when compared to a single-ended amplifier
under the same conditions. This increase in attainable output
power assumes that the amplifier is not current limited and
that the output signal is not clipped. To ensure minimum
output signal clipping when choosing an amplifier’s closedloop gain, refer to the AUDIO POWER AMPLIFIER DESIGN
section. Under rare conditions, with unique combinations of
high power supply voltage and high closed loop gain settings, the LM4951 may exhibit low frequency oscillations.
Another advantage of the differential bridge output is no net
DC voltage across the load. This is accomplished by biasing
AMP1’s and AMP2’s outputs at half-supply. This eliminates
the coupling capacitor that single supply, single-ended amplifiers require. Eliminating an output coupling capacitor in a
typical single-ended configuration forces a single-supply amplifier’s half-supply bias voltage across the load. This increases internal IC power dissipation and may permanently
damage loads such as speakers.
PDMAX-MONOBTL = 4(VDD)
(4)
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection. Applications that employ a voltage regulator typically use a 10µF in parallel with a 0.1µF filter capacitors to
stabilize the regulator’s output, reduce noise on the supply
line, and improve the supply’s transient response. However,
their presence does not eliminate the need for a local 1.0µF
tantalum bypass capacitance connected between the
LM4951’s supply pins and ground. Do not substitute a ceramic capacitor for the tantalum. Doing so may cause oscil-
Bridge Mode (2)
The maximum power dissipation point given by Equation (2)
must not exceed the power dissipation given by Equation
(3):
11
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LM4951
Application Information
LM4951
Application Information
The gain of the internal amplifiers remains unity until the
voltage on the bypass pin reaches VDD/2. As soon as the
voltage on the bypass pin is stable, there is a delay to
prevent undesirable output transients (“click and pops”). After this delay, the device becomes fully functional.
(Continued)
lation. Keep the length of leads and traces that connect
capacitors between the LM4951’s power supply pin and
ground as short as possible. Connecting a larger capacitor,
CBYPASS, between the BYPASS pin and ground improves
the internal bias voltage’s stability and improves the amplifier’s PSRR. The PSRR improvements increase as the bypass pin capacitor value increases. Too large, however,
increases turn-on time and can compromise the amplifier’s
click and pop performance. The selection of bypass capacitor values, especially CBYPASS, depends on desired PSRR
requirements, click and pop performance (as explained in
the section, SELECTING EXTERNAL COMPONENTS),
system cost, and size constraints.
AUDIO POWER AMPLIFIER DESIGN
Audio Amplifier Design: Driving 1.8W into an 8Ω BTL
The following are the desired operational parameters:
Power Output
8Ω
Input Level
0.3VRMS (max)
Input Impedance
20kΩ
Bandwidth
50Hz–20kHz ± 0.25dB
The design begins by specifying the minimum supply voltage
necessary to obtain the specified output power. One way to
find the minimum supply voltage is to use the Output Power
vs Power Supply Voltage curve in the Typical Performance
Characteristics section. Another way, using Equation (7), is
to calculate the peak output voltage necessary to achieve
the desired output power for a given load impedance. To
account for the amplifier’s dropout voltage, two additional
voltages, based on the Clipping Dropout Voltage vs Power
Supply Voltage in the Typical Performance Characteristics curves, must be added to the result obtained by Equation (7). The result is Equation (8).
MICRO-POWER SHUTDOWN
The LM4951 features an active-low micro-power shutdown
mode. When active, the LM4951’s micro-power shutdown
feature turns off the amplifier’s bias circuitry, reducing the
supply current. The low 0.01µA typical shutdown current is
achieved by applying a voltage to the SHUTDOWN pin that
is as near to GND as possible. A voltage that is greater than
GND may increase the shutdown current.
There are a few methods to control the micro-power shutdown. These include using a single-pole, single-throw switch
(SPST), a microprocessor, or a microcontroller. When using
a switch, connect the SPST switch between the shutdown
pin and VDD. Select normal amplifier operation by closing the
switch. Opening the switch applies GND to the SHUTDOWN
pin activating micro-power shutdwon.The switch and internal
pull-down resistor guarantee that the SHUTDOWN pin will
not float. This prevents unwanted state changes. In a system
with a microprocessor or a microcontroller, use a digital
output to apply the active-state voltage to the SHUTDOWN
pin.
(7)
VDD = VOUTPEAK + VODTOP + VODBOT
SELECTING EXTERNAL COMPONENTS
(8)
The commonly used 7.5V supply voltage easily meets this.
The additional voltage creates the benefit of headroom,
allowing the LM4951 to produce peak output power in excess of 1.8W without clipping or other audible distortion. The
choice of supply voltage must also not create a situation that
violates of maximum power dissipation as explained above
in the Power Dissipation section. After satisfying the
LM4951’s power dissipation requirements, the minimum differential gain needed to achieve 1.8W dissipation in an 8Ω
BTL load is found using Equation (9).
Input Capacitor Value Selection
Two quantities determine the value of the input coupling
capacitor: the lowest audio frequency that requires amplification and desired output transient suppression.
As shown in Figure 1, the input resistor (Ri) and the input
capacitor (Ci) produce a high pass filter cutoff frequency that
is found using Equation (6).
(6)
fc = 1/2πRiCi
As an example when using a speaker with a low frequency
limit of 50Hz, Ci, using Equation (6) is 0.159µF. The 0.39µF
CINA shown in Figure 1 allows the LM4951 to drive high
efficiency, full range speaker whose response extends below
30Hz.
(9)
Thus, a minimum gain of 12.6 allows the LM4951’s to reach
full output swing and maintain low noise and THD+N performance. For this example, let AV-BTL = 13. The amplifier’s
overall BTL gain is set using the input (Ri) and feedback (Rf)
resistors of the first amplifier in the series BTL configuration.
Additionaly, AV-BTL is twice the gain set by the first amplifier’s
Ri and Rf. With the desired input impedance set at 20kΩ, the
feedback resistor is found using Equation (10).
OPTIMIZING CLICK AND POP REDUCTION
PERFORMANCE
The LM4951 contains circuitry that eliminates turn-on and
shutdown transients ("clicks and pops"). For this discussion,
turn-on refers to either applying the power supply voltage or
when the micro-power shutdown mode is deactivated.
As the VDD/2 voltage present at the BYPASS pin ramps to its
final value, the LM4951’s internal amplifiers are configured
as unity gain buffers. An internal current source charges the
capacitor connected between the BYPASS pin and GND in a
controlled manner. Ideally, the input and outputs track the
voltage applied to the BYPASS pin.
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1.8WRMS
Load Impedance
Rf / Ri = AV-BTL / 2
(10)
The value of Rf is 130kΩ (choose 191kΩ, the closest value).
The nominal output power is 1.8W.
12
LM4951
Application Information
(Continued)
The result is
The last step in this design example is setting the amplifier’s
-3dB frequency bandwidth. To achieve the desired ± 0.25dB
pass band magnitude variation limit, the low frequency response must extend to at least one-fifth the lower bandwidth
limit and the high frequency response must extend to at least
five times the upper bandwidth limit. The gain variation for
both response limits is 0.17dB, well within the ± 0.25dBdesired limit. The results are an
fL = 50Hz / 5 = 10Hz
(11)
fL = 20kHz x 5 = 100kHz
(12)
1 / (2πx20kΩx10Hz) = 0.795µF
Use a 0.82µF capacitor, the closest standard value.
The product of the desired high frequency cutoff (100kHz in
this example) and the differential gain AVD, determines the
upper passband response limit. With AVD = 7 and fH =
100kHz, the closed-loop gain bandwidth product (GBWP) is
700kHz. This is less than the LM4951’s 3.5MHz GBWP. With
this margin, the amplifier can be used in designs that require
more differential gain while avoiding performance restricting
bandwidth limitations.
and an
RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT
Figures 2–4 show the recommended two-layer PC board
layout that is optimized for the SD10A. This circuit is designed for use with an external 7.5V supply 8Ω (min) speakers.
These circuit boards are easy to use. Apply 7.5V and ground
to the board’s VDD and GND pads, respectively. Connect a
speaker between the board’s OUTA and OUTB outputs.
As mentioned in the SELECTING EXTERNAL COMPONENTS section, Ri and Ci create a highpass filter that sets
the amplifier’s lower bandpass frequency limit. Find the coupling capacitor’s value using Equation (13).
Ci = 1 / 2πRifL
(13)
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LM4951
Demonstration Board Layout
200942F8
FIGURE 2. Recommended TS SE PCB Layout:
Top Silkscreen
200942F7
FIGURE 3. Recommended TS SE PCB Layout:
Top Layer
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14
LM4951
Demonstration Board Layout
(Continued)
200942F6
FIGURE 4. Recommended TS SE PCB Layout:
Bottom Layer
15
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LM4951
Revision History
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Rev
Date
Description
1.0
5/19/05
Added the TL (LM4951TL) Mktg
Outline per Nisha P.
1.1
6/13/05
Added the micro SMD pkg drawing.
1.2
7/12/05
Edited graphic F5, then re-released
D/S to the WEB per Nisha P. (MC)
1.3
7/27/05
Changed the Typ values of eos ( on
the 7.5V and 3.3V EC tables ) from
20 to 10, then re-released D/S to the
WEB per Nisha P. (MC)
1.4
10/19/05
Text edits, then released D/S to the
WEB.
1.5
10/26/05
Edited 200942 29, then re-released
D/S to the WEB.
1.6
11/01/05
Added the X1, X2, and X3 values on
the TLA09ZZA mktg outline, then
re-released D/S to the WEB per
Nisha.
16
LM4951
Physical Dimensions
inches (millimeters) unless otherwise noted
Order Number LM4951SD
NS Package Number SDC10A
Order Number LM4951TL, TLX
NS Package Number TLA09ZZA
X1 = 1.463 ± 0.03, X2 = 1.463 ± 0.03, X3 = 0.600 ± 0.75
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LM4951 Wide Voltage Range 1.8 Watt Audio Amplifier
Notes
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
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NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS
WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.
2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.
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