LM4665 [NSC]
Filterless High Efficiency 1W Switching Audio Amplifier; 滤波的高效1W切换音频放大器
| 型号： | LM4665 |
| 厂家： | 
National Semiconductor |
| 描述： | Filterless High Efficiency 1W Switching Audio Amplifier |
| 文件： | 总18页 (文件大小：1014K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
December 2002
LM4665
Filterless High Efficiency 1W Switching Audio Amplifier
General Description
Key Specifications
The LM4665 is a fully integrated single-supply high efficiency
switching audio amplifier. It features an innovative modulator
that eliminates the LC output filter used with typical switching
amplifiers. Eliminating the output filter reduces parts count,
simplifies circuit design, and reduces board area. The
LM4665 processes analog inputs with a delta-sigma modu-
lation technique that lowers output noise and THD when
compared to conventional pulse width modulators.
j
Efficiency at 100mW into 8Ω transducer
75%(typ)
80%(typ)
3mA(typ)
j
Efficiency at 400mW into 8Ω transducer
j
j
j
j
Total quiescent power supply current (3V)
Total shutdown power supply current (3V) 0.01µA(typ)
Single supply range (MSOP & LD)
Single supply range (ITL) (Note 11)
2.7V to 5.5V
2.7V to 3.8V
The LM4665 is designed to meet the demands of mobile
phones and other portable communication devices. Operat-
ing on a single 3V supply, it is capable of driving 8Ω trans-
ducer loads at a continuous average output of 400mW with
less than 2%THD+N.
Features
n No output filter required for inductive transducers
n Selectable gain of 6dB (2V/V) or 12dB (4V/V)
n Very fast turn on time: 5ms (typ)
n User selectable shutdown High or Low logic level
n Minimum external components
The LM4665 has high efficiency with an 8Ω transducer load
compared to a typical Class AB amplifier. With a 3V supply,
the IC’s efficiency for a 100mW power level is 75%, reaching
80% at 400mW output power.
n "Click and pop" suppression circuitry
n Micro-power shutdown mode
n Short circuit protection
n micro SMD, LLP, and MSOP packages (no heat sink
required)
The LM4665 features a low-power consumption shutdown
mode. Shutdown may be enabled by either a logic high or
low depending on the mode selection. Connecting the Shut-
down Mode pin to either VDD (high) or GND (low) enables
the Shutdown pin to be driven in a likewise manner to
activate shutdown.
Applications
n Mobile phones
n PDAs
The LM4665 has fixed selectable gain of either 6dB or 12dB.
The LM4665 has short circuit protection against a short from
the outputs to VDD, GND or across the outputs.
n Portable electronic devices
Typical Application
20027001
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2002 National Semiconductor Corporation
DS200270
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Connection Diagrams
Mini Small Outline (MSOP) Package
9 Bump micro SMD Package
20027023
Top View
Order Number LM4665MM
20027036
Top View
See NS Package Number MUB10A
Order Number LM4665ITL, LM4665ITLX
See NS Package Number TLA09AAA
LLP Package
MSOP Marking
200270C5
Top View
G - Boomer Family
C5 - LM4665MM
200270D0
Top View
Order Number LM4665LD
See NS Package Number LDA10B
micro SMD Marking
200270C6
Top View
X - Date Code
200270C9
Top View
Z - Plant Code
T- Die Traceability
G - Boomer Family
A2 - LM4665ITL
XY - Date Code
TT- Die Traceability
Bottom Line-Part Number
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2
Absolute Maximum Ratings (Notes 1,
θJC (MSOP)
56˚C/W
180˚C/W
63˚C/W
12˚C/W
θJA (micro SMD)
2)
θJA (LLP) (Note 10)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
θJC (LLP) (Note 10)
Soldering Information
See AN-1112 "microSMD Wafers Level Chip Scale
Package."
Supply Voltage (Note 1)
Storage Temperature
6.0V
−65˚C to +150˚C
VDD + 0.3V ≥ V ≥ GND - 0.3V
Internally Limited
2.0kV
Voltage at Any Input Pin
Power Dissipation (Note 3)
ESD Susceptibility (Note 4)
ESD Susceptibility (Note 5)
Junction Temperature (TJ)
Thermal Resistance
Operating Ratings (Note 2)
Temperature Range
200V
TMIN ≤ TA ≤ TMAX
−40˚C ≤ TA ≤ 85˚C
2.7V ≤ VDD ≤ 5.5V
2.7V ≤ VDD ≤ 3.8V
150˚C
Supply Voltage (MSOP & LD)
Supply Voltage (ITL) (Note11)
θJA (MSOP)
190˚C/W
Electrical Characteristics VDD = 5V (Notes 1, 2, 11)
<
The following specifications apply for VDD = 5V, RL = 8Ω + 33µH, measurement bandwidth is 10Hz - 22kHz unless other-
wise specified. Limits apply for TA = 25˚C.
LM4665
Units
Symbol
IDD
Parameter
Conditions
VIN = 0V, No Load
Typical
(Note 6)
14
Limit
(Limits)
(Notes 7, 8)
Quiescent Power Supply Current
mA
mA
VIN = 0V, 8Ω + 22µH Load
VSD = VSD Mode (Note 9)
VSD Mode = VDD
14.5
0.1
ISD
Shutdown Current
5.0
1.4
0.4
1.4
0.4
1.4
0.4
5.5
6.5
11.5
12.5
µA (max)
V (min)
V (max)
V (min)
V (max)
V (min)
V (max)
dB (min)
dB (max)
dB (min)
dB (max)
mV
VSDIH
VSDIL
VSDIH
VSDIL
VGSIH
VGSIL
Shutdown Voltage Input High
Shutdown Voltage Input Low
Shutdown Voltage Input High
Shutdown Voltage Input Low
Gain Select Input High
1.2
VSD Mode = VDD
1.1
VSD Mode = GND
1.2
VSD Mode = GND
1.1
1.2
Gain Select Input Low
1.1
AV
AV
Closed Loop Gain
Closed Loop Gain
VGain Select = VDD
VGain Select = GND
6
12
VOS
Output Offset Voltage
Wake-up Time
10
5
TWU
Po
ms
Output Power
THD+N = 3% (max), fIN = 1kHz
PO = 400mWRMS, fIN = 1kHz
VGain Select = VDD, Gain = 6dB
VGain Select = GND, Gain = 12dB
1.4
0.8
100
65
W
THD+N
Total Harmonic Distortion+Noise
%
kΩ
RIN
Differential Input Resistance
Power Supply Rejection Ratio
kΩ
PSRR
VRipple = 100mVRMS,
fRipple = 217Hz, AV = 6dB
Inputs Terminated
52
dB
CMRR
eN
Common Mode Rejection Ratio
Output Noise Voltage
VRipple = 100mVRMS,
43
dB
µV
fRipple = 217Hz, AV = 6dB
A-Weighted filter, VIN = 0V
350
3
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Electrical Characteristics VDD = 3V (Notes 1, 2)
<
The following specifications apply for VDD = 3V, and RL = 8Ω + 33µH, measurement bandwidth is 10Hz - 22kHz unless oth-
erwise specified. Limits apply for TA = 25˚C.
LM4665
Units
Symbol
IDD
Parameter
Conditions
VIN = 0V, No Load
Typical
(Note 6)
3.0
Limit
(Notes 7, 8)
7.0
(Limits)
Quiescent Power Supply Current
mA (max)
mA
VIN = 0V, 8Ω + 22µH Load
VSD = VSD Mode (Note 9)
VSD Mode = VDD
3.5
ISD
Shutdown Current
0.01
1.0
5.0
1.4
0.4
1.4
0.4
1.4
0.4
5.5
6.5
11.5
12.5
µA (max)
V (min)
V (max)
V (min)
V (max)
V (min)
V (max)
dB (min)
dB (max)
dB (min)
dB (max)
mV
VSDIH
VSDIL
VSDIH
VSDIL
VGSIH
VGSIL
Shutdown Voltage Input High
Shutdown Voltage Input Low
Shutdown Voltage Input High
Shutdown Voltage Input Low
Gain Select Input High
VSD Mode = VDD
0.8
VSD Mode = GND
1.0
VSD Mode = GND
0.8
1.0
Gain Select Input Low
0.8
AV
AV
Closed Loop Gain
Closed Loop Gain
VGain Select = VDD
VGain Select = GND
6
12
VOS
Output Offset Voltage
Wake-up Time
10
5
TWU
Po
ms
Output Power
THD+N = 2% (max), fIN = 1kHz
PO = 100mWRMS, fIN = 1kHz
VGain Select = VDD, Gain = 6dB
VGain Select = GND, Gain = 12dB
400
0.4
100
65
350
mW (min)
% (max)
kΩ
THD+N
Total Harmonic Distortion+Noise
RIN
Differential Input Resistance
kΩ
VRipple = 100mVRMS
,
PSRR
Power Supply Rejection Ratio
fRipple = 217Hz, AV = 6dB,
Inputs Terminated
52
dB
VRipple = 100mVRMS
,
CMRR
eN
Common Mode Rejection Ratio
Output Noise Voltage
39
dB
µV
fRipple = 217Hz, AV = 6dB
A-Weighted filter, VIN = 0V
350
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 LM4665, T
= 150˚C.
DMAX
JMAX
A
JA
JMAX
See the Efficiency and Power Dissipation versus Output Power curves for more information.
Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
Note 5: Machine Model, 220 pF–240 pF 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 Mode pin
SD
should be connected to V or GND and the Shutdown pin should be driven as close as possible to V or GND for minimum shutdown current and the best THD
DD
DD
performance in PLAY mode. See the Application Information section under SHUTDOWN FUNCTION for more information.
Note 10: The exposed-DAP of the LDA10B package should be electrically connected to GND.
Note 11: The LM4665 in the micro SMD package (ITL) has an operating range of 2.7V - 3.8V for 8Ω speaker loads. The supply range may be increased as speaker
impedance is increased. It is not recommended that 4Ω loads be used with the micro SMD package. To increase the supply voltage operating range, see Figure 2
and INCREASING SUPPLY VOLTAGE RANGE in the Application Information section for more information.
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.
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Typical Performance Characteristics
THD+N vs Frequency
VDD = 5V, RL = 8Ω + 33µH
POUT = 400mW, 30kHz BW
THD+N vs Frequency
VDD = 3V, RL = 8Ω + 33µH
POUT = 100mW, 30kHz BW
200270E0
200270D9
THD+N vs Frequency
VDD = 3.3V, RL = 4Ω + 33µH
POUT = 300mW, 30kHz BW
THD+N vs Power Out
VDD = 5V, RL = 8Ω + 33µH
f = 1kHz, 22kHz BW
200270D8
200270D5
THD+N vs Power Out
VDD = 3V, RL = 8Ω + 33µH
f = 1kHz, 22kHz BW
THD+N vs Power Out
VDD = 3.3V, RL = 4Ω + 33µH
f = 1kHz, 22kHz BW
200270E2
200270E1
5
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Typical Performance Characteristics (Continued)
THD+N vs Common-Mode Voltage
VDD = 5V, RL = 8Ω + 33µH, f = 1kHz
POUT = 400mW, 22kHz BW
THD+N vs Common-Mode Voltage
VDD = 3V, RL = 8Ω + 33µH, f = 1kHz
POUT = 100mW, 22kHz BW
20027031
20027032
CMRR vs Frequency
VDD = 5V, RL = 8Ω + 33µH
VCM = 100mVRMS Sine Wave, 80kHz BW
CMRR vs Frequency
VDD = 3V, RL = 8Ω + 33µH
VCM = 100mVRMS Sine Wave, 80kHz BW
20027095
20027098
PSRR vs DC Common-Mode Voltage
PSRR vs DC Common-Mode Voltage
VDD = 5V, RL = 8Ω + 33µH
VRipple = 100mVRMS, fRipple = 217Hz Sine Wave
VDD = 3V, RL = 8Ω + 33µH
VRipple = 100mVRMS, fRipple = 217Hz Sine Wave
20027096
20027097
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6
Typical Performance Characteristics (Continued)
PSRR vs Frequency
VDD = 5V, RL = 8Ω + 33µH
VCM = 100mVRMSSine Wave, 22kHz BW
PSRR vs Frequency
VDD = 3V, RL = 8Ω + 33µH
VCM = 100mVRMSSine Wave, 22kHz BW
20027099
20027094
Efficiency (top trace) and
Efficiency (top trace) and
Power Dissipation (bottom trace) vs Output Power
Power Dissipation (bottom trace) vs Output Power
<
<
VDD = 5V, RL = 8Ω + 33µH, f = 1kHz, THD 3%
VDD = 3V, RL = 8Ω + 33µH, f = 1kHz, THD 2%
200270A1
200270A2
Efficiency (top trace) and
Power Dissipation (bottom trace) vs Output Power
Gain Threshold Voltages
VDD = 3V - 5V
<
VDD = 3.3V, RL = 4Ω + 33µH, f = 1kHz, THD 2%
200270A3
200270A5
7
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Typical Performance Characteristics (Continued)
Output Power vs Supply Voltage
Output Power vs Supply Voltage
RL = 16Ω + 33µH, f = 1kHz
RL = 8Ω + 33µH, f = 1kHz
200270D7
200270E3
Output Power vs Supply Voltage
Shutdown Hysteresis Voltage
RL = 4Ω + 33µH, f = 1kHz
VDD = 5V, SD Mode = GND (SD Low)
200270D6
200270A7
Shutdown Hysteresis Voltage
Shutdown Hysteresis Voltage
VDD = 3V, SD Mode = GND (SD Low)
VDD = 5V, SD Mode = GND (SD High)
200270A8
200270A9
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Typical Performance Characteristics (Continued)
Shutdown Hysteresis Voltage
VDD = 3V, SD Mode = GND (SD High)
Supply Current
vs Supply Voltage
RL = 8Ω + 33µH
200270B0
20027002
tential "sink" for the small excess of input power over audio
band output power. The LM4665 dissipates only a fraction of
the excess power requiring no additional PCB area or cop-
per plane to act as a heat sink.
Application Information
GENERAL AMPLIFIER FUNCTION
The output signals generated by the LM4665 consist of two,
BTL connected, output signals that pulse momentarily from
near ground potential to VDD. The two outputs can pulse
independently with the exception that they both may never
pulse simultaneously as this would result in zero volts across
the BTL load. The minimum width of each pulse is approxi-
mately 160ns. However, pulses on the same output can
occur sequentially, in which case they are concatenated and
appear as a single wider pulse to achieve an effective 100%
duty cycle. This results in maximum audio output power for a
given supply voltage and load impedance. The LM4665 can
achieve much higher efficiencies than class AB amplifiers
while maintaining acceptable THD performance.
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 LM4665 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 LM4665 also
offers the possibility of DC input coupling which eliminates
the two external AC coupling, DC blocking capacitors. The
LM4665 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 LM4665 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.
The short (160ns) drive pulses emitted at the LM4665 out-
puts means that good efficiency can be obtained with mini-
mal load inductance. The typical transducer load on an audio
amplifier is quite reactive (inductive). For this reason, the
load can act as it’s own filter, so to speak. This "filter-less"
switching amplifier/transducer load combination is much
more attractive economically due to savings in board space
and external component cost by eliminating the need for a
filter.
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
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
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 LM4665 and the load results is lower output
power and decreased efficiency. Higher trace resistance
between the supply and the LM4665 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
>
(
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 LM4665 and in the
transducer load. The amount of power dissipation in the
LM4665 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-
9
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Application Information (Continued)
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 LM4665 has an internal resistor connected between the
Shutdown Mode and Shutdown pins. The purpose of this
resistor is to eliminate any unwanted state changes when
the Shutdown pin is floating, as long as the Shutdown Mode
pin is connected to GND or VDD. When the Shutdown Mode
pin is properly connected, the LM4665 will enter the shut-
down state when the Shutdown pin is left floating or if not
floating, when the shutdown voltage has crossed the corre-
sponding threshold for the logic level assigned by the Shut-
down Mode pin voltage. To minimize the supply current while
in the shutdown state, the Shutdown pin should be driven to
the same potential as the Shutdown Mode pin or left floating.
The amount of additional current due to the internal shut-
down resistor can be found by Equation (1) below.
The rising and falling edges are necessarily short in relation
to the minimum pulse width (160ns), having approximately
2ns rise and fall times, typical, depending on parasitic output
capacitance. 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 standpoint, this is an aggressive waveform that can
radiate or conduct to other components in the system and
cause interference. 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.
(VSD MODE - VSD) / 60kΩ
(1)
With only a 0.5V difference between the Shutdown Mode
voltage and the Shutdown voltage an additional 8.3µA of
current will be drawn while in the shutdown state.
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 LM4665. 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
LM4665. A 1µF tantalum capacitor is recommended.
GAIN SELECTION FUNCTION
The LM4665 has fixed selectable gain to minimize external
components, increase flexibility and simplify design. For a
differential gain of 6dB (2V/V), the Gain Select pin should be
permanently connected to VDD or driven to a logic high level.
For a differential gain of 12dB (4V/V), the Gain Select pin
should be permanently connected to GND or driven to a
logic low level. The gain of the LM4665 can be switched
while the amplifier is in PLAY mode driving a load with a
signal without damage to the IC. The voltage on the Gain
Select pin should be switched quickly between GND (logic
low) and VDD (logic high) to eliminate any possible audible
artifacts from appearing at the output. For typical threshold
voltages for the Gain Select function, refer to the Gain
Threshold Voltages graph in the Typical Performance
Characteristics section.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4665 contains shutdown circuitry that reduces current
draw to less than 0.01µA. In addition, the LM4665 contains a
Shutdown Mode pin allowing the designer to designate
whether the shutdown circuitry is activated by either a High
level logic signal or a Low level logic signal. The Shutdown
Mode pin should be permanently connected to either GND
(Low) or VDD (High). The LM4665 may then be placed into
shutdown by toggling the Shutdown pin to the same state as
the Shutdown Mode pin. For simplicity’s sake, this is called
"Shutdown same", as the LM4665 enters into a shutdown
state whenever the two pins are in the same logic state. The
trigger point for either shutdown high or shutdown low 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
LM4665 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 greater than GND and less than VDD on the
Shutdown pin when in PLAY mode.
INCREASING SUPPLY VOLTAGE RANGE
When using the micro SMD package (ITL), the operating
supply voltage range is 2.7V - 3.8V with an 8Ω speaker load.
To increase the operating supply voltage range, four Schot-
tky diodes (D1 - D4) can be used to control the over and
undershoot of the output pulse waveform (See Figure 2
below). To reduce THD+N, small value capacitors in the
range of 10pF - 33pF (CN1 & CN2) can also be added as
needed. The diodes should be placed as close to the micro
SMD package as possible.
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Application Information (Continued)
200270E5
FIGURE 2. Increased Supply Voltage Operating Range for the micro SMD package
SINGLE-ENDED CIRCUIT CONFIGURATIONS
200270C4
FIGURE 3. Single-Ended Input, Shutdown High and Gain of 6dB Configuration
11
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Application Information (Continued)
200270C2
FIGURE 4. Single-Ended Input, Shutdown High and Gain of 12dB Configuration
200270C3
FIGURE 5. Single-Ended Input, Shutdown Low and Gain of 6dB Configuration
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Application Information (Continued)
200270C1
FIGURE 6. Single-Ended Input, Shutdown Low and Gain of 12dB Configuration
REFERENCE DESIGN BOARD SCHEMATIC
200270B1
FIGURE 7.
13
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The commonly used Audio Precision analyzer is differential,
but its ability to accurately reject fast pulses of 160nS width
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 differ-
ential output to a single ended output. Depending on the
audio transformer’s characteristics, there may be some at-
tenuation of the audio signal which needs to be taken into
account for correct measurement of performance.
Application Information (Continued)
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.
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 -0.35dB (4%). 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.
LM4665 MSOP BOARD ARTWORK
Composite View
Silk Screen
200270B3
200270B2
Top Layer
Bottom Layer
200270B5
200270B4
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14
Application Information (Continued)
LM4665 LLP BOARD ARTWORK
Composite View
Silk Screen
200270D1
200270D2
Top Layer
Bottom Layer
200270D3
200270D4
15
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Application Information (Continued)
LM4665 micro SMD BOARD ARTWORK
Composite View
Silk Screen
200270C8
200270C7
Top Layer
Bottom Layer
200270C0
200270B9
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16
Physical Dimensions inches (millimeters) unless otherwise noted
9 Bump micro SMD
Order Number LM4665ITL, LM4665ITLX
NS Package Number TLA09AAA
X1 = 1.514 X2 = 1.514 X3 = 0.600
Mini Small Outline (MSOP)
Order Number LM4665MM
NSPackage Number MUB10A
17
www.national.com
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LLP
Order Number LM4665LD
NSPackage Number LDA10B
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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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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.
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