LM4673SDX [NSC]

IC 2.65 W, 1 CHANNEL, AUDIO AMPLIFIER, DSO8, LLP-8, Audio/Video Amplifier;
LM4673SDX
型号: LM4673SDX
厂家: National Semiconductor    National Semiconductor
描述:

IC 2.65 W, 1 CHANNEL, AUDIO AMPLIFIER, DSO8, LLP-8, Audio/Video Amplifier

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November 1, 2007  
LM4673ꢀ  
Filterless, 2.65W, Mono, Class D Audio Power Amplifier  
General Description  
Key Specifications  
The LM4673 is a single supply, high efficiency, 2.65W, mono,  
Class D audio amplifier. A low noise, filterless PWM architec-  
ture eliminates the output filter, reducing external component  
count, board area consumption, system cost, and simplifying  
design.  
■ꢀ  
Efficiency at 3.6V, 400mW into 8speaker  
88% (typ)  
80% (typ)  
■ꢀ  
Efficiency at 3.6V, 100mW into 8speaker  
The LM4673 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 4speaker  
load at a continuous average output of 2.1W with less than  
1% THD+N. Its flexible power supply requirements allow op-  
eration from 2.4V to 5.5V.  
■ꢀ  
Efficiency at 5V, 1W into 8speaker  
86% (typ)  
■ꢀQuiescent current, 3.6V supply  
2.1mA (typ)  
■ꢀ  
0.01µA (typ)  
Total shutdown power supply current  
The LM4673 has high efficiency with speaker loads compared  
to a typical Class AB amplifier. With a 3.6V supply driving an  
8speaker, the IC's efficiency for a 100mW power level is  
80%, reaching 88% at 400mW output power.  
2.4V to 5.5V  
78dB  
■ꢀSingle supply range  
■ꢀPSRR, f = 217Hz  
The LM4673 features a low-power consumption shutdown  
mode. Shutdown may be enabled by driving the Shutdown  
pin to a logic low (GND).  
Features  
Mono Class D Operation  
No output filter required for inductive loads  
The gain of the LM4673 is externally configurable which al-  
lows independent gain control from multiple sources by sum-  
ming the signals. Output short circuit and thermal overload  
protection prevent the device from damage during fault con-  
ditions.  
Externally configurable gain  
Very fast turn on time: 17μs (typ)  
Minimum external components  
"Click and pop" suppression circuitry  
Micro-power shutdown mode  
Available in space-saving 0.4mm pitch micro SMD and  
LLPTm packages  
Applications  
Mobile phones  
PDAs  
Portable electronic devices  
Boomer® is a registered trademark of National Semiconductor Corporation.  
© 2007 National Semiconductor Corporation  
201522  
www.national.com  
Typical Application  
201522j3  
FIGURE 1. Typical Audio Amplifier Application Circuit  
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2
 
Connection Diagrams  
9 Bump micro SMD Package  
micro SMD Marking  
20152257  
Top View  
X — Date Code  
T— Die Traceability  
G — Boomer Family  
G4 — LM4673TM  
20152236  
Top View  
Order Number LM4673TM  
See NS Package Number TMD09GGA  
Leadless Leadframe Package (LLP)  
LLP Marking  
20152202  
20152201  
Top View  
Z — Plant Code  
Top View  
Order Number LM4673SD  
See NS Package Number SDA08A  
Contact NSC Sales Office for Availability  
XY — Date Code  
TT — Die Traceability  
L4673 — LM4673SD  
3
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Thermal Resistance  
ꢁθJA (micro SMD)  
ꢁθJA (LLP)  
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.  
99.1°C/W  
73°C/W  
Soldering Information  
See AN-1112 "microSMD Wafers Level Chip Scale  
Package."  
Supply Voltage (Note 1)  
Storage Temperature  
Voltage at Any Input Pin  
6.0V  
−65°C to +150°C  
VDD + 0.3V V GND - 0.3V  
Operating Ratings (Notes 1, 2)  
Temperature Range  
Power Dissipation (Note 3)  
ESD Susceptibility, all other pins (Note 4)  
ESD Susceptibility (Note 5)  
Internally Limited  
2.0kV  
200V  
TMIN TA TMAX  
Supply Voltage  
−40°C TA 85°C  
2.4V VDD 5.5V  
Junction Temperature (TJMAX  
)
150°C  
Electrical Characteristics (Notes 1, 2)  
The following specifications apply for AV = 2V/V (RI = 150k), RL = 15µH + 8Ω + 15µH unless otherwise specified. Limits apply for  
TA = 25°C.  
LM4673  
Units  
Symbol  
Parameter  
Conditions  
VI = 0V, AV = 2V/V,  
Typical  
Limit  
(Limits)  
(Note 6)  
(Notes 7, 8)  
|VOS  
|
Differential Output Offset Voltage  
5
mV (max)  
VDD = 2.4V to 5.0V  
|IIH|  
|IIL|  
Logic High Input Current  
Logic Low Input Current  
VDD = 5.0V, VI = 5.5V  
17  
0.9  
2.6  
2.1  
1.7  
2.6  
2.1  
1.7  
100  
5
μA (max)  
μA (max)  
mA (max)  
mA  
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  
VIN = 0V, RL = 8Ω, VDD = 5.0V  
VIN = 0V, RL = 8Ω, VDD = 3.6V  
VIN = 0V, RL = 8Ω, VDD = 2.4V  
3.75  
2.9  
2.3  
mA (max)  
IDD  
Quiescent Power Supply Current  
Shutdown Current  
VSHUTDOWN = 0V  
ISD  
0.01  
1
μA (max)  
VDD = 2.4V to 5.0V  
VSDIH  
VSDIL  
ROSD  
Shutdown voltage input high  
Shutdown voltage input low  
Output Impedance  
1.4  
0.4  
V (min)  
V (max)  
VSHUTDOWN = 0.4V  
100  
kΩ  
270k/RI  
330k/RI  
V/V (min)  
V/V (max)  
AV  
Gain  
300k/RI  
Resistance from Shutdown Pin to  
GND  
RSD  
300  
kΩ  
RL = 15μH + 4Ω + 15μH  
THD = 10% (max)  
f = 1kHz, 22kHz BW  
VDD = 5V  
2.65  
1.3  
W
W
VDD = 3.6V  
VDD = 2.5V  
550  
mW  
PO  
Output Power  
RL = 15μH + 4Ω + 15μH  
THD = 1% (max)  
f = 1kHz, 22kHz BW  
VDD = 5V  
2.15  
1.06  
450  
W
W
mW  
VDD = 3.6V  
VDD = 2.5V  
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LM4673  
Typical  
Units  
(Limits)  
Symbol  
Parameter  
Conditions  
Limit  
(Note 6)  
(Notes 7, 8)  
RL = 15μH + 8Ω + 15μH  
THD = 10% (max)  
f = 1kHz, 22kHz BW  
VDD = 5V  
1.7  
870  
350  
W
VDD = 3.6V  
VDD = 2.5V  
mW  
mW  
PO  
Output Power  
RL = 15μH + 8Ω + 15μH  
THD = 1% (max)  
f = 1kHz, 22kHz BW  
VDD = 5V  
1.24  
650  
W
mW  
mW  
%
VDD = 3.6V  
600  
VDD = 2.5V  
300  
VDD = 5V, PO = 0.1W, f = 1kHz  
VDD = 3.6V, PO = 0.1W, f = 1kHz  
VDD = 2.5V, PO = 0.1W, f = 1kHz  
0.03  
0.02  
0.02  
THD+N  
PSRR  
Total Harmonic Distortion + Noise  
%
%
VRipple = 200mVPP Sine,  
fRipple = 217Hz, VDD = 3.6, 5V  
Inputs to AC GND, CI = 2μF  
78  
dB  
Power Supply Rejection Ratio  
(Input Referred)  
VRipple = 200mVPP Sine,  
fRipple = 1kHz, VDD = 3.6, 5V  
Inputs to AC GND, CI = 2μF  
72  
97  
30  
dB  
dB  
VDD = 5V, PO = 1WRMS  
SNR  
Signal to Noise Ratio  
VDD = 3.6V, f = 20Hz – 20kHz  
Inputs to AC GND, CI = 2μF  
No Weighting  
μVRMS  
Output Noise  
εOUT  
(Input Referred)  
VDD = 3.6V, Inputs to AC GND  
CI = 2μF, A Weighted  
23  
70  
μVRMS  
VDD = 3.6V, VRipple = 1VPP Sine  
fRipple = 217Hz  
Common Mode Rejection Ratio  
(Input Referred)  
CMRR  
dB  
TWU  
TSD  
Wake-up Time  
Shutdown Time  
VDD = 3.6V  
17  
μs  
μs  
140  
VDD = 3.6V, POUT = 400mW  
RL = 8Ω  
88  
86  
%
%
Efficiency  
η
VDD = 5V, POUT = 1W  
RL = 8Ω  
5
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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 TJMAX, θJA, and the ambient temperature TA. The maximum  
allowable power dissipation is PDMAX = (TJMAX–TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4673, TJMAX = 150°C.  
The typical θJA is 99.1°C/W for the micro SMD package.  
Note 4: Human body model, 100pF discharged through a 1.5kresistor.  
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 ISD by a maximum of 2µA. The Shutdown pin  
should be driven as close as possible to GND for minimal shutdown current and to VDD 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 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.  
2.  
CI  
Input AC coupling capacitor which blocks the DC voltage at the amplifier's input terminals.  
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Typical Performance Characteristics  
THD + N vs Output Power  
THD + N vs Output Power  
f = 1kHz, RL = 8Ω  
f = 1kHz, RL = 4Ω  
20152240  
20152241  
THD + N vs Frequency  
VDD = 2.5V, POUT = 100mW, RL = 8Ω  
THD + N vs Frequency  
VDD = 3.6V, POUT = 150mW, RL = 8Ω  
20152242  
20152243  
7
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THD + N vs Frequency  
VDD = 5V, POUT = 200mW, RL = 8Ω  
THD + N vs Frequency  
VDD = 2.5V, POUT = 100mW, RL = 4Ω  
20152244  
20152245  
THD + N vs Frequency  
VDD = 3.6V, POUT = 100mW, RL = 4Ω  
THD + N vs Frequency  
VDD = 5V, POUT = 150mW, RL = 4Ω  
20152246  
20152247  
Efficiency vs. Output Power  
Efficiency vs. Output Power  
RL = 4Ω, f = 1kHz  
RL = 8Ω, f = 1kHz  
20152249  
20152248  
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Power Dissipation vs. Output Power  
Power Dissipation vs. Output Power  
RL = 4Ω, f = 1kHz  
RL = 8Ω, f = 1kHz  
20152250  
20152251  
Output Power vs. Supply Voltage  
Output Power vs. Supply Voltage  
RL = 4Ω, f = 1kHz  
RL = 8Ω, f = 1kHz  
20152252  
20152253  
PSRR vs. Frequency  
VDD = 3.6V ,VRIPPLE = 200mVP-P, RL = 8Ω  
CMRR vs. Frequency  
VDD = 3.6V, VCM = 1VP-P, RL = 8Ω  
20152254  
20152255  
9
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Supply Current vs. Supply Voltage  
No Load  
20152256  
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Application Information  
GENERAL AMPLIFIER FUNCTION  
ply create a voltage drop. The voltage loss on the traces  
between the LM4673 and the load results is lower output  
power and decreased efficiency. Higher trace resistance be-  
tween the supply and the LM4673 has the same effect as a  
poorly regulated supply, increased 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 corresponding  
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.  
The LM4673 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 LM4673 are differential,  
the two signals cancel each other. This results in no net volt-  
age across the speaker, thus there is no load current during  
an idle state, conserving power.  
With an input signal applied, the duty cycle (pulse width) of  
the LM4673 outputs changes. For increasing output voltages,  
the duty cycle of VO1 increases, while the duty cycle of VO2  
decreases. For decreasing output voltages, the converse oc-  
curs, 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.  
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 fil-  
ter the power supply line.  
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 pre-  
venting unwanted interference.  
POWER DISSIPATION AND EFFICIENCY  
In general terms, efficiency is considered to be the ratio of  
useful work output divided by the total energy required to pro-  
duce it with the difference being the power dissipated, typi-  
cally, 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 be-  
ing transduced is dissipated in the LM4673 and in the trans-  
ducer load. The amount of power dissipation in the LM4673  
is very low. This is because the ON resistance of the switches  
used to form the output waveforms is typically less than  
0.25. This leaves only the transducer load as a potential  
"sink" for the small excess of input power over audio band  
output power. The LM4673 dissipates only a fraction of the  
excess power requiring no additional PCB area or copper  
plane to act as a heat sink.  
As the distance from the LM4673 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.  
Ferrite chip inductors placed close to the LM4673 may be  
needed to reduce EMI radiation. The value of the ferrite chip  
is very application specific.  
POWER SUPPLY BYPASSING  
As with any power amplifier, proper supply bypassing is crit-  
ical for low noise performance and high power supply rejec-  
tion ratio (PSRR). The capacitor (CS) location should be as  
close as possible to the LM4673. Typical applications employ  
a voltage regulator with a 10µF and a 0.1µF bypass capacitors  
that increase supply stability. These capacitors do not elimi-  
nate the need for bypassing on the supply pin of the LM4673.  
A 4.7µF tantalum capacitor is recommended.  
DIFFERENTIAL AMPLIFIER EXPLANATION  
As logic supply voltages continue to shrink, designers are in-  
creasingly turning to differential analog signal handling to  
preserve signal to noise ratios with restricted voltage swing.  
The LM4673 is a fully differential amplifier that features dif-  
ferential input and output stages. A differential amplifier am-  
plifies the difference between the two input signals. Tradition-  
al 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 LM4673 also offers the  
possibility of DC input coupling which eliminates the two ex-  
ternal AC coupling, DC blocking capacitors. The LM4673 can  
be used, however, as a single ended input amplifier while still  
retaining it's fully differential benefits. In fact, completely un-  
related signals may be placed on the input pins. The LM4673  
simply amplifies the difference between 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 characteristic of the differential am-  
plifier reduces sensitivity to ground offset related noise injec-  
tion, especially important in high noise applications.  
SHUTDOWN FUNCTION  
In order to reduce power consumption while not in use, the  
LM4673 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 Ta-  
bles 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 LM4673 may be  
disabled with shutdown voltages in between ground and sup-  
ply, the idle current will be greater than the typical 0.01µA  
value.  
The LM4673 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 LM4673 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 minimize 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  
PCB LAYOUT CONSIDERATIONS  
As output power increases, interconnect resistance (PCB  
traces and wires) between the amplifier, load and power sup-  
11  
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due to the internal shutdown resistor can be found by Equa-  
tion (1) below.  
differential input configuration shown in Figure 2. Equation (2)  
above is used to determine the value of the Ri resistors for a  
desired gain.  
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.  
(VSD - GND) / 300kΩ  
(1)  
With only a 0.5V difference, an additional 1.7µA of current will  
be drawn while in the shutdown state.  
PROPER SELECTION OF EXTERNAL COMPONENTS  
The LM4673 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-  
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 de-  
pending on the source or if a DC voltage needs to be blocked  
from a source.  
The gain of the LM4673 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).  
AV = 2 * 150 k/ Ri (V/V)  
(2)  
It is recommended that resistors with 1% tolerance or better  
be used to set the gain of the LM4673. The Ri resistors should  
be placed close to the input pins of the LM4673. 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 LM4673. Noise coupled onto input traces  
which are physically close to each other will be common mode  
and easily rejected by the LM4673.  
SINGLE-ENDED CIRCUIT CONFIGURATIONS  
The LM4673 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 application  
configuration. The equations for Gain, Equation (2), and fre-  
quency response, Equation (3), hold for the single-ended  
configuration as shown in Figure 5.  
Input capacitors may be needed for some applications or  
when the source is single-ended (see Figures 3, 5). Input ca-  
pacitors are needed to block any DC voltage at the source so  
that the DC voltage seen between the input terminals of the  
LM4673 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.  
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 resis-  
tor, Ci3 and Ri3, are found by calculating the parallel combi-  
nation of all Civalues and then all Ri values. Equations (4) and  
(5) below are for any number of single-ended sources.  
fC = 1 / (2πRi Ci ) (Hz)  
(3)  
Ci3 = Ci1 + Ci2 + Cin ... (F)  
(4)  
(5)  
The input capacitors may also be used to remove low audio  
frequencies. Small speakers cannot reproduce low bass fre-  
quencies so filtering may be desired . When the LM4673 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. Capacitors  
with a tolerance of 10% or better are recommended for  
impedance matching.  
Ri3 = 1 / (1/Ri1 + 1/Ri2 + 1/Rin ...) (Ω)  
The LM4673 may also use a combination of single-ended and  
differential sources. A typical application with one single-end-  
ed source and one differential source is shown in Figure 7.  
Using the principle of superposition, the external component  
values can be determined with the above equations corre-  
sponding to the configuration.  
DIFFERENTIAL CIRCUIT CONFIGURATIONS  
The LM4673 can be used in many different circuit configura-  
tions. The simplest and best performing is the DC coupled,  
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12  
20152222  
FIGURE 2. Differential Input Configuration  
20152223  
FIGURE 3. Differential Input Configuration with Input Capacitors  
13  
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20152224  
FIGURE 4. Dual Differential Input Configuration  
20152225  
FIGURE 5. Single-Ended Input Configuration  
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20152226  
FIGURE 6. Dual Single-Ended Input Configuration  
20152227  
FIGURE 7. Dual Input with a Single-Ended Input and a Differential Input  
15  
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REFERENCE DESIGN BOARD SCHEMATIC  
20152228  
FIGURE 8.  
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 out-  
put to a single ended output. Depending on the audio  
transformer's characteristics, there may be some attenuation  
of the audio signal which needs to be taken into account for  
correct measurement of performance.  
In addition to the minimal parts required for the application  
circuit, a measurement filter is provided on the evaluation cir-  
cuit 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 component on the  
outputs. The grounded capacitive filter elements attenuate  
this component at the board to reduce the high frequency  
CMRR requirement placed on the analysis instruments.  
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 (300) 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 outputs. 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 differen-  
tial, necessitating a differential input on any analysis instru-  
ment connected to it. Most lab instruments that feature BNC  
connectors on their inputs are NOT differential responding  
because the ring of the BNC is usually grounded.  
www.national.com  
16  
LM4673SD Demo Board Artwork  
Top Silkscreen  
Top Layer  
20152234  
20152235  
Composite View  
Internal Layer 1  
20152232  
20152231  
Internal Layer 2  
Bottom Silkscreen  
20152233  
20152230  
17  
www.national.com  
Bottom Layer  
20152229  
www.national.com  
18  
LM4673TM Demo Board Artwork  
Top Silkscreen  
Top Layer  
20152263  
20152261  
20152259  
20152264  
Composite View  
Internal Layer 1  
20152260  
Internal Layer 2  
Bottom Silkscreen  
20152262  
19  
www.national.com  
Bottom Layer  
20152258  
www.national.com  
20  
Revision History  
Rev  
1.0  
1.1  
Date  
Description  
12/16/05  
02/28/06  
Initial WEB released.  
Taken out “Future Product”, then re-WEBd  
the datasheet.  
1.2  
1.3  
04/06/06  
11/01/07  
Added the TM and SD demo boards, then  
released to the WEB (per Royce).  
Deleted a sentence under the SHUTDOWN  
FUNCTION section.  
21  
www.national.com  
Physical Dimensions inches (millimeters) unless otherwise noted  
9 Bump micro SMD  
Order Number LM4673TM  
NS Package Number TMD09GGA  
X1 = 1.405 X2 = 1.405 X3 = 0.600  
LLP  
Order Number LM4673SD  
NS Package Number SDA08A  
www.national.com  
22  
Notes  
23  
www.national.com  
Notes  
For more National Semiconductor product information and proven design tools, visit the following Web sites at:  
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Analog University  
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Clock Conditioners  
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Green Compliance  
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Ethernet  
Interface  
Quality and Reliability www.national.com/quality  
LVDS  
Reference Designs  
Feedback  
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