LM4671 [NSC]
Filterless High Efficiency 2.5W Switching Audio Amplifier; 滤波的高效2.5W开关音频放大器
| 型号： | LM4671 |
| 厂家： | 
National Semiconductor |
| 描述： | Filterless High Efficiency 2.5W Switching Audio Amplifier |
| 文件： | 总18页 (文件大小：966K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
March 2005
LM4671
Filterless High Efficiency 2.5W Switching Audio
Amplifier
General Description
Key Specifications
The LM4671 is a single supply, high efficiency 2.5W switch-
ing audio amplifier. A low noise, filterless PWM architecture
eliminates the output filter, reducing external component
count, board area consumption, system cost, and simplifying
design.
j
Efficiency at 3.6V, 100mW into 8Ω speaker 80% (typ)
Efficiency at 3.6V, 400mW into 8Ω speaker 88% (typ)
j
j
j
j
j
Efficiency at 5V, 1W into 8Ω speakerr
Quiescent current, 3.6V supply
Total shutdown power supply current
Single supply range
86% (typ)
2.8mA (typ)
0.01µA (typ)
2.4V to 5.5V
The LM4671 is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing on a single 5V supply, it is capable of driving a 4Ω
speaker load at a continuous average output of 2.1W with
less than 1% THD+N. Its flexible power supply requirements
allow operation from 2.4V to 5.5V.
Features
n No output filter required for inductive loads
n Externally configurable gain
n Very fast turn on time: 1ms (typ)
n Minimum external components
n "Click and pop" suppression circuitry
n Micro-power shutdown mode
The LM4671 has high efficiency with speaker loads com-
pared to a typical Class AB amplifier. With a 3V supply
driving an 8Ω speaker, the IC’s efficiency for a 100mW
power level is 80%, reaching 88% at 400mW output power.
The LM4671 features a low-power consumption shutdown
mode. Shutdown may be enabled by driving the Shutdown
pin to a logic low (GND).
n Available in space-saving microSMD package
The gain of the LM4671 is externally configurable which
allows independent gain control from multiple sources by
summing the signals.
Applications
n Mobile phones
n PDAs
n Portable electronic devices
Typical Application
201073J3
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation
DS201073
www.national.com
Connection Diagrams
9 Bump micro SMD Package
micro SMD Marking
201073C6
Top View
X — Date Code
T— Die Traceability
G — Boomer Family
E7 — LM4671ITL
20107336
Top View
Order Number LM4671ITL, LM4671ITLX
See NS Package Number TLA09AAA
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2
Absolute Maximum Ratings (Notes 1, 2)
Thermal Resistance
θJA (micro SMD)
220˚C/W
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Soldering Information
See AN-1112 "microSMD Wafers Level Chip Scale
Package."
Supply Voltage (Note 1)
Storage Temperature
6.0V
−65˚C to +150˚C
Voltage at Any Input Pin
Power Dissipation (Note 3)
VDD + 0.3V ≥ V ≥ GND - 0.3V
Internally Limited
Operating Ratings (Note 1) (Note 2)
Temperature Range
ESD Susceptibility, all other pins (Note 4)
ESD Susceptibility (Note 5)
2.0kV
200V
TMIN ≤ TA ≤ TMAX
−40˚C ≤ TA ≤ 85˚C
2.4V ≤ VDD ≤ 5.5V
Supply Voltage
Junction Temperature (TJMAX
)
150˚C
Electrical Characteristics (Notes 1, 2)
The following specifications apply for AV = 2V/V (RI = 150kΩ), RL = 15µH + 8Ω + 15µH unless otherwise specified. Limits ap-
ply for TA = 25˚C.
LM4671
Units
Symbol
Parameter
Conditions
Typical
Limit
(Limits)
(Note 6)
(Notes 7, 8)
VI = 0V, AV = 2V/V,
VDD = 2.4V to 5.0V
|VOS
|
Differential Output Offset Voltage
5
mV (max)
dB (min)
PSRRGSM GSM Power Supply Rejection Ratio VDD = 2.4V to 5.0V
61
VDD = 2.4V to 5.0V
GSM Common Mode Rejection
CMRRGSM
VIC = VDD/2 to 0.5V,
68
dB (min)
Ratio
VIC = VDD/2 to VDD – 0.8V
VDD = 5.0V, VI = 5.5V
|IIH
|
Logic High Input Current
Logic Low Input Current
17
0.9
6.4
3.8
2.0
100
5
µA (max)
µA (max)
mA (max)
mA
|IIL|
VDD = 5.0V, VI = –0.3V
VIN = 0V, No Load, VDD = 5.0V
VIN = 0V, No Load, VDD = 3.6V
VIN = 0V, No Load, VDD =2.4V
VSHUTDOWN = 0V
IDD
Quiescent Power Supply Current
6.2
3.0
mA (max)
ISD
Shutdown Current
0.01
1
µA (max)
VDD = 2.4V to 5.0V
VSDIH
VSDIL
ROSD
Shutdown voltage input high
Shutdown voltage input low
Output Impedance
1.2
1.1
100
1.4
0.4
V (min)
V (max)
kΩ
VSHUTDOWN = 0.4V
270kΩ/RI
330kΩ/RI
V/V (min)
V/V (max)
AV
Gain
300kΩ/RI
Resistance from Shutdown Pin to
GND
RSD
300
kΩ
RL = 15µH + 4Ω + 15µH
THD = 10% (max)
f = 1kHz, 22kHz BW
VDD = 5V
2.5
1.3
520
W
W
VDD = 3.6V
VDD = 2.5V
mW
PO
Output Power
RL = 15µH + 4Ω + 15µH
THD = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V
2.21
1.06
420
W
W
VDD = 3.6V
VDD = 2.5V
mW
3
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Electrical Characteristics (Notes 1, 2)
The following specifications apply for AV = 2V/V (RI = 150kΩ), RL = 15µH + 8Ω + 15µH unless otherwise specified. Limits
apply for TA = 25˚C. (Continued)
LM4671
Units
(Limits)
Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Notes 7, 8)
RL = 15µH + 8Ω + 15µH
THD = 10% (max)
f = 1kHz, 22kHz BW
VDD = 5V
17
W
mW
W
VDD = 3.6V
870
425
VDD = 2.5V
PO
Output Power
RL = 15µH + 8Ω + 15µH
THD = 1% (max)
f = 1kHz, 22kHz BW
VDD = 5V
1.19
700
350
W
mW
W
VDD = 3.6V
600
VDD = 2.5V
VDD = 5V, PO = 0.1WRMS
,
0.09
0.04
0.12
0.05
%
%
%
%
f = 1kHz
VDD = 3.6V, PO = 0.1WRMS
,
,
,
THD+N
Total Harmonic Distortion + Noise
f = 1kHz
VDD = 3.6V, PO = 0.1WRMS
f = 5kHz
VDD = 3.6V, PO = 0.1WRMS
f = 10kHz
VDD = 3.6V, 5V
VRipple = 200mVPP Sine,
fRipple = 217Hz
61.8
59.8
dB
dB
dB
dB
Inputs to AC GND, CI = 2µF
VDD = 3.6V, 5V
VRipple = 200mVPP Sine,
fRipple = 1kHz
PSRR
Power Supply Rejection Ratio
Inputs to AC GND, CI = 2µF
VDD = 3.6V, 5V
VRipple = 200mVPP Sine,
fRipple = 10kHz
48.65
65.71
Inputs to AC GND, CI = 2µF
VDD = 3.6V, 5V
VRipple = 200mVPP Sine,
fRipple = 217Hz
fIN = 1kHz, PO = 10mWRMS
VDD = 5V, PO = 1WRMS
VDD = 3.6V, f = 20Hz – 20kHz
Inputs to AC GND, CI = 2µF
No Weighting
SNR
Signal to Noise Ratio
Output Noise
93
58
dB
µVRMS
eOUT
VDD = 3.6V, Inputs to AC GND
CI = 2µF, A Weighted
VDD = 3.6V, VRipple = 1VPP Sine
fRipple = 217Hz
38
µVRMS
dB
CMRR
Common Mode Rejection Ratio
68.3
TWU
TSD
Wake-up Time
Shutdown Time
VDD = 3.6V
17
µs
µs
140
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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
, θ , and the ambient temperature T . The maximum
A
JMAX JA
allowable power dissipation is P
= (T
–T )/θ or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4671, T
= 150˚C.
DMAX
JMAX
A
JA
JMAX
The typical θ is 220˚C/W for the microSMD package.
JA
Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor.
Note 5: Machine Model, 220pF–240pF discharged through all pins.
Note 6: Typical specifications are specified at 25˚C 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 by a maximum of 2µA. The Shutdown pin should
SD
be driven as close as possible to GND for minimal shutdown current and to V
section under SHUTDOWN FUNCTION for more information.
for the best THD performance in PLAY mode. See the Application Information
DD
Note 10: The performance graphs were taken using the Audio Precision AUX-0025 Switching Amplifier measurement Filter in series with the LC filter on the demo
board.
External Components Description
(Figure 1)
Components
Functional Description
1.
CS
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.
Input AC coupling capacitor which blocks the DC voltage at the amplifier’s input terminals.
2.
CI
5
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Typical Performance Characteristics
THD+N vs Frequency
VDD = 2.4V, RL = 15µH+4Ω+15µH,
PO = 375mW, 22kHz BW
THD+N vs Frequency
VDD = 3.6V, RL = 15µH+4Ω+15µH,
PO = 750mW, 22kHz BW
20107303
20107304
THD+N vs Frequency
VDD = 5V, RL = 15µH+4Ω+15µH,
PO = 1.5mW, 22kHz BW
THD+N vs Frequency
VDD = 2.4V, RL = 15µH+8Ω+15µH,
PO = 200mW, 22kHz BW
20107305
20107306
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Typical Performance Characteristics (Continued)
THD+N vs Frequency
VDD = 3.6V, RL = 15µH+8Ω+15µH,
PO = 500mW, 22kHz BW
THD+N vs Frequency
VDD = 5V, RL = 15µH+8Ω+15µH,
PO = 1W, 22kHz BW
20107307
20107308
THD+N vs Output Power
VDD = 5V, RL = 15µH+4Ω+15µH,
f = 1kHz, 22kHz BW
THD+N vs Output Power
VDD = 5V, RL = 15µH+8Ω+15µH,
f = 1kHz, 22kHz BW
20107310
20107309
7
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Typical Performance Characteristics (Continued)
CMRR vs Frequency
VDD = 3.6V, RL = 15µH+8Ω+15µH,
Vripple = 1Vp-p, 22kHz BW
PSRR vs Frequency
VDD = 3.6V, RL = 15µH+8Ω+15µH,
Vripple = 200mVp-p, 22kHz BW
20107311
20107312
Efficiency vs Output Power
RL = 15µH+4Ω+15µH,
f = 1kHz, 22kHz BW
Efficiency vs Output Power
RL = 15µH+8Ω+15µH,
f = 1kHz, 22kHz BW
20107314
20107313
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Typical Performance Characteristics (Continued)
Power Dissipation vs Output Power
RL = 15µH+4Ω+15µH,
Power Dissipation vs Output Power
RL = 15µH+8Ω+15µH,
f = 1kHz, 22kHz BW
f = 1kHz, 22kHz BW
20107316
20107315
Output Power vs Supply Voltage
RL = 15µH+4Ω+15µH,
VDD = 3.6V
Output Power vs Supply Voltage
RL = 15µH+8Ω+15µH,
VDD = 3.6V
20107318
20107317
9
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Typical Performance Characteristics (Continued)
Gain vs Supply Voltage
Supply Current vs Supply Voltage
Rin = 150kΩ
RL = 15µH+8Ω+15µH
20107319
20107320
Shutdown Current vs Supply Voltage
RL = 15µH+8Ω+15µH
20107321
Application Information
GENERAL AMPLIFIER FUNCTION
POWER DISSIPATION AND EFFICIENCY
The LM4671 features a filterless modulation scheme. The
differential outputs of the device switch at 300kHz from VDD
to GND. When there is no input signal applied, the two
outputs (VO1 and VO2) switch with a 50% duty cycle, with
both outputs in phase. Because the outputs of the LM4671
are differential, the two signals cancel each other. This re-
sults in no net voltage across the speaker, thus there is no
load current during an idle state, conserving power.
In general terms, efficiency is considered to be the ratio of
useful work output divided by the total energy required to
produce it with the difference being the power dissipated,
typically, in the IC. The key here is “useful” work. For audio
systems, the energy delivered in the audible bands is con-
sidered useful including the distortion products of the input
signal. Sub-sonic (DC) and super-sonic components
>
(
22kHz) are not useful. The difference between the power
flowing from the power supply and the audio band power
being transduced is dissipated in the LM4671 and in the
transducer load. The amount of power dissipation in the
LM4671 is very low. This is because the ON resistance of the
switches used to form the output waveforms is typically less
than 0.25Ω. This leaves only the transducer load as a po-
tential "sink" for the small excess of input power over audio
With an input signal applied, the duty cycle (pulse width) of
the LM4671 outputs changes. For increasing output volt-
ages, the duty cycle of VO1 increases, while the duty cycle of
VO2 decreases. For decreasing output voltages, the con-
verse occurs, the duty cycle of VO2 increases while the duty
cycle of VO1 decreases. The difference between the two
pulse widths yields the differential output voltage.
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Ferrite chip inductors placed close to the LM4671 may be
needed to reduce EMI radiation. The value of the ferrite chip
is very application specific.
Application Information (Continued)
band output power. The LM4671 dissipates only a fraction of
the excess power requiring no additional PCB area or cop-
per plane to act as a heat sink.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection ratio (PSRR). The capacitor (CS) location should be
as close as possible to the LM4671. Typical applications
employ a voltage regulator with a 10µF and a 0.1µF bypass
capacitors that increase supply stability. These capacitors do
not eliminate the need for bypassing on the supply pin of the
LM4671. A 1µF tantalum capacitor is recommended.
DIFFERENTIAL AMPLIFIER EXPLANATION
As logic supply voltages continue to shrink, designers are
increasingly turning to differential analog signal handling to
preserve signal to noise ratios with restricted voltage swing.
The LM4671 is a fully differential amplifier that features
differential input and output stages. A differential amplifier
amplifies the difference between the two input signals. Tra-
ditional audio power amplifiers have typically offered only
single-ended inputs resulting in a 6dB reduction in signal to
noise ratio relative to differential inputs. The LM4671 also
offers the possibility of DC input coupling which eliminates
the two external AC coupling, DC blocking capacitors. The
LM4671 can be used, however, as a single ended input
amplifier while still retaining it’s fully differential benefits. In
fact, completely unrelated signals may be placed on the
input pins. The LM4671 simply amplifies the difference be-
tween the signals. A major benefit of a differential amplifier is
the improved common mode rejection ratio (CMRR) over
single input amplifiers. The common-mode rejection charac-
teristic of the differential amplifier reduces sensitivity to
ground offset related noise injection, especially important in
high noise applications.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4671 contains shutdown circuitry that reduces current
draw to less than 0.01µA. The trigger point for shutdown is
shown as a typical value in the Electrical Characteristics
Tables and in the Shutdown Hysteresis Voltage graphs
found in the Typical Performance Characteristics section.
It is best to switch between ground and supply for minimum
current usage while in the shutdown state. While the
LM4671 may be disabled with shutdown voltages in between
ground and supply, the idle current will be greater than the
typical 0.01µA value. Increased THD may also be observed
with voltages less than VDD on the Shutdown pin when in
PLAY mode.
The LM4671 has an internal resistor connected between
GND and Shutdown pins. The purpose of this resistor is to
eliminate any unwanted state changes when the Shutdown
pin is floating. The LM4671 will enter the shutdown state
when the Shutdown pin is left floating or if not floating, when
the shutdown voltage has crossed the threshold. To mini-
mize the supply current while in the shutdown state, the
Shutdown pin should be driven to GND or left floating. If the
Shutdown pin is not driven to GND, the amount of additional
resistor current due to the internal shutdown resistor can be
found by Equation (1) below.
PCB LAYOUT CONSIDERATIONS
As output power increases, interconnect resistance (PCB
traces and wires) between the amplifier, load and power
supply create a voltage drop. The voltage loss on the traces
between the LM4671 and the load results is lower output
power and decreased efficiency. Higher trace resistance
between the supply and the LM4671 has the same effect as
a poorly regulated supply, increase ripple on the supply line
also reducing the peak output power. The effects of residual
trace resistance increases as output current increases due
to higher output power, decreased load impedance or both.
To maintain the highest output voltage swing and corre-
sponding peak output power, the PCB traces that connect
the output pins to the load and the supply pins to the power
supply should be as wide as possible to minimize trace
resistance.
(VSD - GND) / 60kΩ
(1)
With only a 0.5V difference, an additional 8.3µA of current
will be drawn while in the shutdown state.
PROPER SELECTION OF EXTERNAL COMPONENTS
The gain of the LM4671 is set by the external resistors, Ri in
Figure 1, The Gain is given by Equation (2) below. Best
THD+N performance is achieved with a gain of 2V/V (6dB).
The use of power and ground planes will give the best
THD+N performance. While reducing trace resistance, the
use of power planes also creates parasite capacitors that
help to filter the power supply line.
AV = 2 * 150 kΩ / Ri (V/V)
(2)
The inductive nature of the transducer load can also result in
overshoot on one or both edges, clamped by the parasitic
diodes to GND and VDD in each case. From an EMI stand-
point, this is an aggressive waveform that can radiate or
conduct to other components in the system and cause inter-
ference. It is essential to keep the power and output traces
short and well shielded if possible. Use of ground planes,
beads, and micro-strip layout techniques are all useful in
preventing unwanted interference.
It is recommended that resistors with 1% tolerance or better
be used to set the gain of the LM4671. The Ri resistors
should be placed close to the input pins of the LM4671.
Keeping the input traces close to each other and of the same
length in a high noise environment will aid in noise rejection
due to the good CMRR of the LM4671. Noise coupled onto
input traces which are physically close to each other will be
common mode and easily rejected by the LM4671.
As the distance from the LM4671 and the speaker increase,
the amount of EMI radiation will increase since the output
wires or traces acting as antenna become more efficient with
length. What is acceptable EMI is highly application specific.
Input capacitors may be needed for some applications or
when the source is single-ended (see Figures 3, 5). Input
capacitors are needed to block any DC voltage at the source
so that the DC voltage seen between the input terminals of
11
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mum design flexibility using the Ri resistors for each input
and Equation (2). Input capacitors can be used with one or
more sources as well to have different frequency responses
depending on the source or if a DC voltage needs to be
blocked from a source.
Application Information (Continued)
the LM4671 is 0V. Input capacitors create a high-pass filter
with the input resistors, Ri. The –3dB point of the high-pass
filter is found using Equation (3) below.
SINGLE-ENDED CIRCUIT CONFIGURATIONS
fC = 1 / (2πRi Ci ) (Hz)
(3)
The LM4671 can also be used with single-ended sources but
input capacitors will be needed to block any DC at the input
terminals. Figure 5 shows the typical single-ended applica-
tion configuration. The equations for Gain, Equation (2), and
frequency response, Equation (3), hold for the single-ended
configuration as shown in Figure 5.
The input capacitors may also be used to remove low audio
frequencies. Small speakers cannot reproduce low bass
frequencies so filtering may be desired . When the LM4671
is using a single-ended source, power supply noise on the
ground is seen as an input signal by the +IN input pin that is
capacitor coupled to ground (See Figures 5 – 7). Setting the
high-pass filter point above the power supply noise frequen-
cies, 217Hz in a GSM phone, for example, will filter out this
noise so it is not amplified and heard on the output. Capaci-
tors with a tolerance of 10% or better are recommended for
impedance matching.
When using more than one single-ended source as shown in
Figure 6, the impedance seen from each input terminal
should be equal. To find the correct values for Ci3 and Ri3
connected to the +IN input pin the equivalent impedance of
all the single-ended sources are calculated. The single-
ended sources are in parallel to each other. The equivalent
capacitor and resistor, Ci3 and Ri3, are found by calculating
the parallel combination of all Civalues and then all Ri val-
ues. Equations (4) and (5) below are for any number of
single-ended sources.
DIFFERENTIAL CIRCUIT CONFIGURATIONS
The LM4671 can be used in many different circuit configu-
rations. The simplest and best performing is the DC coupled,
differential input configuration shown in Figure 2. Equation
(2) above is used to determine the value of the Ri resistors
for a desired gain.
Ci3 = Ci1 + Ci2 + Cin ... (µF)
(4)
(5)
Input capacitors can be used in a differential configuration as
shown in Figure 3. Equation (3) above is used to determine
the value of the Ci capacitors for a desired frequency re-
sponse due to the high-pass filter created by Ci and Ri.
Equation (2) above is used to determine the value of the Ri
resistors for a desired gain
Ri3 = 1 / (1/Ri1 + 1/Ri2 + 1/Rin ...) (Ω)
The LM4671 may also use a combination of single-ended
and differential sources. A typical application with one single-
ended source and one differential source is shown in Figure
7. Using the principle of superposition, the external compo-
nent values can be determined with the above equations
corresponding to the configuration.
The LM4671 can be used to amplify more than one audio
source. Figure 4 shows a dual differential input configuration.
The gain for each input can be independently set for maxi-
201073I7
FIGURE 2. Differential input configuration
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Application Information (Continued)
201073I8
FIGURE 3. Differential input configuration with input capacitors
201073I9
FIGURE 4. Dual differential input configuration
13
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Application Information (Continued)
201073J0
FIGURE 5. Single-ended input configuration
201073J1
FIGURE 6. Dual single-ended input configuration
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Application Information (Continued)
201073J2
FIGURE 7. Dual input with a single-ended input and a differential input
15
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Application Information (Continued)
REFERENCE DESIGN BOARD SCHEMATIC
201073J4
FIGURE 8.
In addition to the minimal parts required for the application
circuit, a measurement filter is provided on the evaluation
circuit board so that conventional audio measurements can
be conveniently made without additional equipment. This is a
balanced input, grounded differential output low pass filter
with a 3dB frequency of approximately 35kHz and an on
board termination resistor of 300Ω (see schematic). Note
that the capacitive load elements are returned to ground.
This is not optimal for common mode rejection purposes, but
due to the independent pulse format at each output there is
a significant amount of high frequency common mode com-
ponent on the outputs. The grounded capacitive filter ele-
ments attenuate this component at the board to reduce the
high frequency CMRR requirement placed on the analysis
instruments.
The commonly used Audio Precision analyzer is differential,
but its ability to accurately reject high frequency signals is
questionable necessitating the on board measurement filter.
When in doubt or when the signal needs to be single-ended,
use an audio signal transformer to convert the differential
output to a single ended output. Depending on the audio
transformer’s characteristics, there may be some attenua-
tion of the audio signal which needs to be taken into account
for correct measurement of performance.
Measurements made at the output of the measurement filter
suffer attenuation relative to the primary, unfiltered outputs
even at audio frequencies. This is due to the resistance of
the inductors interacting with the termination resistor (300Ω)
and is typically about -0.25dB (3%). In other words, the
voltage levels (and corresponding power levels) indicated
through the measurement filter are slightly lower than those
that actually occur at the load placed on the unfiltered out-
puts. This small loss in the filter for measurement gives a
lower output power reading than what is really occurring on
the unfiltered outputs and its load.
Even with the grounded filter the audio signal is still differ-
ential, necessitating a differential input on any analysis in-
strument connected to it. Most lab instruments that feature
BNC connectors on their inputs are NOT differential re-
sponding because the ring of the BNC is usually grounded.
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Application Information (Continued)
LM4671 micro SMD BOARD ARTWORK
Composite View
Silk Screen
Internal Layer 1, GND
Bottom Layer
201073J6
201073J9
Top Layer
201073K0
201073J7
Internal Layer 2, GND
201073J8
201073J5
17
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Physical Dimensions inches (millimeters) unless otherwise noted
9 Bump micro SMD
Order Number LM4671ITL, LM4671ITLX
NS Package Number TLA09AAA
X1 = 1.514 X2 = 1.514 X3 = 0.600
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相关型号：
LM4671ITLX/NOPB
IC 2.5 W, 1 CHANNEL, AUDIO AMPLIFIER, PBGA9, MICRO, SMD-9, Audio/Video Amplifier
NSC
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