LM4903 1 Watt Audio Power Amplifier 1 W

LM4903 1 Watt Audio Power Amplifier 1 W
LM4903
1 Watt Audio Power Amplifier
General Description
Key Specifications
The LM4903 is an audio power amplifier primarily designed
for demanding applications in mobile phones and other portable communication device applications. It is capable of
delivering 1 watt of continuous average power to an 8Ω BTL
load with less than 1% distortion (THD+N) from a 5VDC
power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4903 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for mobile phone and other low voltage applications where minimal power consumption is a primary requirement.
The LM4903 features a low-power consumption shutdown
mode, which is achieved by driving the shutdown pin with
logic low. Additionally, the LM4903 features an internal thermal shutdown protection mechanism.
The LM4903 contains advanced pop & click circuitry which
eliminates noise which would otherwise occur during turn-on
and turn-off transitions.
The LM4903 is unity-gain stable and can be configured by
external gain-setting resistors.
j Improved PSRR at 217Hz & 1KHz
62dB
j Power Output at 5.0V, 1% THD, 8Ω
1.07W (typ)
j Power Output at 3.0V, 1% THD, 4Ω
525mW (typ)
j Power Output at 3.0V, 1% THD, 8Ω
390mW (typ)
j Shutdown Current
0.1µA (typ)
Features
n
n
n
n
n
n
n
n
Available in space-saving MSOP package
Ultra low current shutdown mode
BTL output can drive capacitive loads
Improved pop & click circuitry eliminates noise during
turn-on and turn-off transitions
2.0 - 5.5V operation
No output coupling capacitors, snubber networks or
bootstrap capacitors required
Unity-gain stable
External gain configuration capability
Applications
n Mobile Phones
n PDAs
n Portable electronic devices
Typical Application
200467D3
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer ® is a registered trademark of National Semiconductor Corporation.
© 2003 National Semiconductor Corporation
DS200467
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LM4903 1 Watt Audio Power Amplifier
February 2003
LM4903
Connection Diagrams
Mini Small Outline (MSOP) Package
200467D1
Top View
Order Number LM4903MM
See NS Package Number MUA08A
MSOP Marking
200467D2
Top View
G - Boomer Family
A4 - LM4903MM
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2
Junction Temperature
(Note 2)
Thermal Resistance
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (Note 10)
θJC (MSOP)
56˚C/W
θJA (MSOP)
190˚C/W
6.0V
Storage Temperature
−65˚C to +150˚C
Operating Ratings
−0.3V to VDD +0.3V
Input Voltage
150˚C
Power Dissipation (Notes 3, 11)
ESD Susceptibility (Note 4)
ESD Susceptibility (Note 5)
Temperature Range
Internally Limited
TMIN ≤ TA ≤ TMAX
2000V
−40˚C ≤ TA ≤ 85˚C
2.0V ≤ VDD ≤ 5.5V
Supply Voltage
200V
Electrical Characteristics VDD = 5V (Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for TA = 25˚C.
LM4903
Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Notes 7, 8)
VIN = 0V, Io = 0A, No Load
3
7
mA (max)
VIN = 0V, Io = 0A, 8Ω Load
4
10
mA (max)
0.8
2.0
µA (max)
IDD
Quiescent Power Supply Current
ISD
Shutdown Current
VSDIH
Shutdown Voltage Input High
1.5
VSDIL
Shutdown Voltage Input Low
1.3
VOS
Output Offset Voltage
ROUT
Output Power
TWU
Wake-up time
THD+N
Total Harmonic Distortion+Noise
Power Supply Rejection Ratio
PSRR
VSD = VGND
V (min)
V (max)
7
Resistor Output to GND (Note 9)
Po
Units
(Limits)
8.5
THD = 1% (max); f = 1 kHz
1.07
50
mV (max)
9.7
kΩ (max)
7.0
kΩ (min)
0.9
W
100
mS (max)
Po = 0.5 Wrms; f = 1kHz
0.2
%
Vripple = 200mV sine p-p
Input terminated with 10Ω
60 (f =
217Hz)
64 (f = 1kHz)
55
dB (min)
Electrical Characteristics VDD = 3V (Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for TA = 25˚C.
LM4903
Symbol
Parameter
Conditions
VIN = 0V, Io = 0A, No Load
Units
(Limits)
Typical
Limit
(Note 6)
(Notes 7, 8)
2
7
mA (max)
3
9
mA (max)
0.1
2.0
µA (max)
IDD
Quiescent Power Supply Current
ISD
Shutdown Current
VSDIH
Shutdown Voltage Input High
1.3
V (min)
VSDIL
Shutdown Voltage Input Low
1.0
V (max)
VOS
Output Offset Voltage
ROUT
Po
VIN = 0V, Io = 0A, 8Ω Load
VSD = VGND
7
Resistor Output to GND (Note 9)
Output Power (8Ω)
(4Ω)
8.5
THD = 1% (max); f = 1 kHz
390
THD = 1% (max); f = 1 kHz
525
50
mV (max)
9.7
kΩ (max)
7.0
kΩ (min)
mW
TWU
Wake-up time
75
mS (max)
THD+N
Total Harmonic Distortion+Noise
Po = 0.25 Wrms; f = 1kHz
0.1
%
PSRR
Power Supply Rejection Ratio
Vripple = 200mV sine p-p
Input terminated with 10Ω
70 (f =
217Hz)
65 (f = 1kHz)
3
55
dB (min)
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LM4903
Absolute Maximum Ratings
LM4903
Electrical Characteristics VDD = 2.6V (Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1, unless otherwise specified. Limits apply for TA = 25˚C.
LM4903
Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Notes 7, 8)
Units
(Limits)
VIN = 0V, Io = 0A, No Load
2.0
mA (max)
VIN = 0V, Io = 0A, 8Ω Load
3.0
mA (max)
VSD = VGND
0.01
IDD
Quiescent Power Supply Current
ISD
Shutdown Current
VSDIH
Shutdown Voltage Input High
1.2
V (min)
VSDIL
Shutdown Voltage Input Low
1.0
V (max)
VOS
Output Offset Voltage
ROUT
Po
5
Resistor Output to GND (Note 9)
8.5
Output Power ( 8Ω )
THD = 1% (max); f = 1 kHz
270
( 4Ω )
THD = 1% (max); f = 1 kHz
325
2.0
µA (max)
50
mV (max)
9.7
kΩ (max)
7.0
kΩ (min)
mW
TWU
Wake-up time
70
mS (max)
THD+N
Total Harmonic Distortion+Noise
Po = 0.15 Wrms; f = 1kHz
0.1
%
Power Supply Rejection Ratio
Vripple = 200mV sine p-p
Input terminated with 10Ω
51 (f =
217Hz)
51 (f = 1kHz)
dB (min)
PSRR
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 LM4903, see power derating
curves for additional information.
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: ROUT is measured from the output pin to ground. This value represents the parallel combination of the 10kΩ output resistors and the two 20kΩ resistors.
Note 10: If the product is in Shutdown mode and VDD exceeds 6V (to a max of 8V VDD), then most of the excess current will flow through the ESD protection circuits.
If the source impedance limits the current to a max of 10mA, then the device will be protected. If the device is enabled when VDD is greater than 5.5V and less than
6.5V, no damage will occur, although operation life will be reduced. Operation above 6.5V with no current limit will result in permanent damage.
Note 11: Maximum power dissipation in the device (PDMAX) occurs at an output power level significantly below full output power. PDMAX can be calculated using
Equation 1 shown in the Application Information section. It may also be obtained from the power dissipation graphs.
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LM4903
External Components Description
(Figure 1)
Components
Functional Description
1.
Ri
Inverting input resistance which sets the closed-loop gain in conjunction with Rf. This resistor also forms a
high pass filter with Ci at fC= 1/(2π RiCi).
2.
Ci
Input coupling capacitor which blocks the DC voltage at the amplifiers input terminals. Also creates a
highpass filter with Ri at fc = 1/(2π RiCi). Refer to the section, Proper Selection of External Components,
for an explanation of how to determine the value of Ci.
3.
Rf
Feedback resistance which sets the closed-loop gain in conjunction with Ri.
4.
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.
5.
CB
Bypass pin capacitor which provides half-supply filtering. Refer to the section, Proper Selection of External
Components, for information concerning proper placement and selection of CB.
Typical Performance Characteristics
THD+N vs Frequency
at VDD = 3V, 8Ω RL, and PWR = 250mW
THD+N vs Frequency
at VDD = 5V, 8Ω RL, and PWR = 500mW
20046730
20046731
THD+N vs Frequency
at VDD = 2.6V, 4Ω RL, and PWR = 150mW
THD+N vs Frequency
at VDD = 2.6V, 8Ω RL, and PWR = 150mW
20046732
20046733
5
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LM4903
Typical Performance Characteristics
(Continued)
THD+N vs Power Out
at VDD = 5V, 8Ω RL, 1kHz
THD+N vs Power Out
at VDD = 3V, 8Ω RL, 1kHz
20046734
20046783
THD+N vs Power Out
at VDD = 2.6V, 4Ω RL, 1kHz
THD+N vs Power Out
at VDD = 2.6V, 8Ω RL, 1kHz
20046784
20046785
Power Supply Rejection Ratio (PSRR) vs Frequency
at VDD = 5V, 8Ω RL
Power Supply Rejection Ratio (PSRR) vs Frequency
at VDD = 5V, 8Ω RL
20046786
20046787
Input terminated with 10Ω
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Input Floating
6
(Continued)
Power Supply Rejection Ratio (PSRR) vs Frequency
at VDD = 3V, 8Ω RL
Power Supply Rejection Ratio (PSRR) vs Frequency
at VDD = 3V, 8Ω RL
20046788
20046789
Input terminated with 10Ω
Input Floating
Power Supply Rejection Ratio (PSRR) vs Frequency
at VDD = 2.6V, 8Ω RL
Power Supply Rejection Ratio (PSRR) vs Frequency
at VDD = 2.6V, 8Ω RL
20046790
20046791
Input terminated with 10Ω
Input Floating
Open Loop Frequency Response, 5V
Open Loop Frequency Response, 3V
20046792
20046793
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LM4903
Typical Performance Characteristics
LM4903
Typical Performance Characteristics
(Continued)
Open Loop Frequency Response, 2.6V
Noise Floor, 5V, 8Ω
80kHz Bandwidth, Input to GND
20046794
20046795
Power Derating Curves
Power Dissipation vs
Output Power, 5V, 8Ω
20046769
20046797
Power Dissipation vs
Output Power, VDD =2.6V
Power Dissipation vs
Output Power, VDD =3V
200467C8
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200467C9
8
LM4903
Typical Performance Characteristics
(Continued)
Shutdown Hysteresis Voltage
5V
Shutdown Hysteresis Voltage
3V
200467A1
200467A3
Shutdown Hysteresis Voltage
2.6V
Output Power vs
Supply Voltage, 8Ω
200467A5
200467A6
Output Power vs
Supply Voltage, 16Ω
Output Power vs
Supply Voltage, 32Ω
200467A7
200467A8
9
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LM4903
Typical Performance Characteristics
(Continued)
Frequency Response vs
Input Capacitor Size
20046754
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10
output pins. Refer to the application information on the
LM4903 reference design board for an example of good heat
sinking. If TJMAX still exceeds 150˚C, then additional
changes must be made. These changes can include reduced supply voltage, higher load impedance, or reduced
ambient temperature. Internal power dissipation is a function
of output power. Refer to the Typical Performance Characteristics curves for power dissipation information for different output powers and output loading.
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4903 has two internal operational amplifiers. The first amplifier’s gain is externally configurable, while the second amplifier is internally fixed in a
unity-gain, inverting configuration. The closed-loop gain of
the first amplifier is set by selecting the ratio of Rf to Ri while
the second amplifier’s gain is fixed by the two internal 20kΩ
resistors. Figure 1 shows that the output of amplifier one
serves as the input to amplifier two which results in both
amplifiers producing signals identical in magnitude, but out
of phase by 180˚. Consequently, the differential gain for the
IC is
POWER SUPPLY BYPASSING
As with any amplifier, proper supply bypassing is critical for
low noise performance and high power supply rejection. The
capacitor location on both the bypass and power supply pins
should be as close to the device as possible. Typical applications employ a 5V regulator with 10µF tantalum or electrolytic capacitor and a ceramic bypass capacitor which aid
in supply stability. This does not eliminate the need for
bypassing the supply nodes of the LM4903. The selection of
a bypass capacitor, especially CB, is dependent upon PSRR
requirements, click and pop performance (as explained in
the section, Proper Selection of External Components),
system cost, and size constraints.
AVD= 2 *(Rf/Ri)
By driving the load differentially through outputs Vo1 and
Vo2, an amplifier configuration commonly referred to as
“bridged mode” is established. Bridged mode operation is
different from the classical single-ended amplifier configuration where one side of the load is connected to ground.
A bridge amplifier design has a few distinct advantages over
the single-ended configuration, as it provides differential
drive to the load, thus doubling output swing for a specified
supply voltage. Four times the output power is possible as
compared to a single-ended amplifier under the same conditions. This increase in attainable output power assumes
that the amplifier is not current limited or clipped. In order to
choose an amplifier’s closed-loop gain without causing excessive clipping, please refer to the Audio Power Amplifier
Design section.
A bridge configuration, such as the one used in LM4903,
also creates a second advantage over single-ended amplifiers. Since the differential outputs, Vo1 and Vo2, are biased
at half-supply, no net DC voltage exists across the load. This
eliminates the need for an output coupling capacitor which is
required in a single supply, single-ended amplifier configuration. Without an output coupling capacitor, the half-supply
bias across the load would result in both increased internal
IC power dissipation and also possible loudspeaker damage.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4903 contains shutdown circuitry that is used to turn off
the amplifier’s bias circuitry. This shutdown feature turns the
amplifier off when logic low is placed on the shutdown pin.
By switching the shutdown pin to GND, the LM4903 supply
current draw will be minimized in idle mode. Idle current is
measured with the shutdown pin connected to GND. The
trigger point for shutdown is shown as a typical value in the
Shutdown Hysteresis Voltage graphs in the Typical Performance Characteristics section. It is best to switch between
ground and supply for maximum performance. While the
device may be disabled with shutdown voltages in between
ground and supply, the idle current may be greater than the
typical value of 0.1µA. In either case, the shutdown pin
should be tied to a definite voltage to avoid unwanted state
changes.
POWER DISSIPATION
Power dissipation is a major concern when designing a
successful amplifier, whether the amplifier is bridged or
single-ended. A direct consequence of the increased power
delivered to the load by a bridge amplifier is an increase in
internal power dissipation. Since the LM4903 has two operational amplifiers in one package, the maximum internal
power dissipation is 4 times that of a single-ended amplifier.
The maximum power dissipation for a given application can
be derived from the power dissipation graphs or from Equation 1.
PDMAX = 4*(VDD)2/(2π2RL)
In many applications, a microcontroller or microprocessor
output is used to control the shutdown circuitry, which provides a quick, smooth transition to shutdown. Another solution is to use a single-throw switch in conjunction with an
external pull-up resistor. This scheme guarantees that the
shutdown pin will not float, thus preventing unwanted state
changes.
PROPER SELECTION OF EXTERNAL COMPONENTS
Proper selection of external components in applications using integrated power amplifiers is critical to optimize device
and system performance. While the LM4903 is tolerant of
external component combinations, consideration to component values must be used to maximize overall system quality.
The LM4903 is unity-gain stable which gives the designer
maximum system flexibility. The LM4903 should be used in
low gain configurations to minimize THD+N values, and
maximize the signal to noise ratio. Low gain configurations
require large input signals to obtain a given output power.
Input signals equal to or greater than 1 Vrms are available
(1)
It is critical that the maximum junction temperature TJMAX of
150˚C is not exceeded. TJMAX can be determined from the
power derating curves by using PDMAX and the PC board foil
area. By adding copper foil, the thermal resistance of the
application can be reduced from the free air value of θJA,
resulting in higher PDMAX values without thermal shutdown
protection circuitry being activated. Additional copper foil can
be added to any of the leads connected to the LM4903. It is
especially effective when connected to VDD, GND, and the
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LM4903
Application Information
LM4903
Application Information
Output Power vs Supply Voltage graphs in the Typical Performance Characteristics section, the supply rail can be
easily found.
5V is a standard voltage in most applications, it is chosen for
the supply rail. Extra supply voltage creates headroom that
allows the LM4903 to reproduce peaks in excess of 1W
without producing audible distortion. At this time, the designer must make sure that the power supply choice along
with the output impedance does not violate the conditions
explained in the Power Dissipation section.
Once the power dissipation equations have been addressed,
the required differential gain can be determined from Equation 2.
(Continued)
from sources such as audio codecs. Please refer to the
section, Audio Power Amplifier Design, for a more complete explanation of proper gain selection.
Besides gain, one of the major considerations is the closedloop bandwidth of the amplifier. To a large extent, the bandwidth is dictated by the choice of external components
shown in Figure 1. The input coupling capacitor, Ci, forms a
first order high pass filter which limits low frequency response. This value should be chosen based on needed
frequency response for a few distinct reasons.
Selection Of Input Capacitor Size
Large input capacitors are both expensive and space hungry
for portable designs. Clearly, a certain sized capacitor is
needed to couple in low frequencies without severe attenuation. But in many cases the speakers used in portable
systems, whether internal or external, have little ability to
reproduce signals below 100Hz to 150Hz. Thus, using a
large input capacitor may not increase actual system performance.
(2)
Rf/Ri = AVD/2
From Equation 2, the minimum AVD is 2.83; use AVD = 3.
Since the desired input impedance was 20kΩ, and with a
AVD impedance of 2, a ratio of 1.5:1 of Rf to Ri results in an
allocation of Ri = 20kΩ and Rf = 30kΩ. The final design step
is to address the bandwidth requirements which must be
stated as a pair of −3dB frequency points. Five times away
from a −3dB point is 0.17dB down from passband response
which is better than the required ± 0.25dB specified.
fL = 100Hz/5 = 20Hz
fH = 20kHz * 5 = 100kHz
As stated in the External Components section, Ri in conjunction with Ci create a highpass filter.
Ci ≥ 1/(2π*20kΩ*20Hz) = 0.397µF; use 0.39µF
The high frequency pole is determined by the product of the
desired frequency pole, fH, and the differential gain, AVD.
With a AVD = 3 and fH = 100kHz, the resulting GBWP =
300kHz which is much smaller than the LM4903 GBWP of
2.5MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4903 can still be used without running into bandwidth
limitations.
The LM4903 is unity-gain stable and requires no external
components besides gain-setting resistors, an input coupling
capacitor, and proper supply bypassing in the typical application. However, if a closed-loop differential gain of greater
than 10 is required, a feedback capacitor (C4) may be
needed as shown in Figure 2 to bandwidth limit the amplifier.
This feedback capacitor creates a low pass filter that eliminates possible high frequency oscillations. Care should be
taken when calculating the -3dB frequency in that an incorrect combination of R3 and C4 will cause rolloff before
20kHz. A typical combination of feedback resistor and capacitor that will not produce audio band high frequency rolloff
is R3 = 20kΩ and C4 = 25pf. These components result in a
-3dB point of approximately 320kHz.
In addition to system cost and size, click and pop performance is effected by the size of the input coupling capacitor,
Ci. A larger input coupling capacitor requires more charge to
reach its quiescent DC voltage (nominally 1/2 VDD). This
charge comes from the output via the feedback and is apt to
create pops upon device enable. Thus, by minimizing the
capacitor size based on necessary low frequency response,
turn-on pops can be minimized.
Besides minimizing the input capacitor size, careful consideration should be paid to the bypass capacitor value. Bypass
capacitor, CB, is the most critical component to minimize
turn-on pops since it determines how fast the LM4903 turns
on. The slower the LM4903’s outputs ramp to their quiescent
DC voltage (nominally 1/2 VDD), the smaller the turn-on pop.
Choosing CB equal to 1.0µF along with a small value of Ci (in
the range of 0.1µF to 0.39µF), should produce a virtually
clickless and popless shutdown function. While the device
will function properly, (no oscillations or motorboating), with
CB equal to 0.1µF, the device will be much more susceptible
to turn-on clicks and pops. Thus, a value of CB equal to
1.0µF is recommended in all but the most cost sensitive
designs.
AUDIO POWER AMPLIFIER DESIGN
A 1W/8Ω Audio Amplifier
Given:
Power Output
Load Impedance
Input Level
Input Impedance
Bandwidth
1 Wrms
8Ω
1 Vrms
20 kΩ
100 Hz–20 kHz ± 0.25 dB
A designer must first determine the minimum supply rail to
obtain the specified output power. By extrapolating from the
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LM4903
Application Information
(Continued)
200467D4
FIGURE 2. HIGHER GAIN AUDIO AMPLIFIER
200467D5
FIGURE 3. DIFFERENTIAL AMPLIFIER CONFIGURATION FOR LM4903
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LM4903
Application Information
(Continued)
200467D6
FIGURE 4. REFERENCE DESIGN BOARD SCHEMATIC
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LM4903
Application Information
(Continued)
LM4903 MSOP BOARD ARTWORK
Composite View
Silk Screen
200467E0
200467D8
Top Layer
Bottom Layer
200467D9
200467D7
Mono LM4903 Reference Design Boards
Bill of Material
Part Description
Quantity
Reference Designator
LM4903 Audio AMP
1
U1
Tantalum Capcitor, 1µF
2
C1, C3
Ceramic Capacitor, 0.39µF
1
C2
Resistor, 20kΩ, 1/10W
2
R2, R3
Resistor, 100kΩ, 1/10W
1
R1
Jumper Header Vertical Mount 2X1 0.100“ spacing
1
J1
15
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LM4903
Application Information
Single-Point Power / Ground Connections
(Continued)
The analog power traces should be connected to the digital
traces through a single point (link). A "Pi-filter" can be helpful
in minimizing High Frequency noise coupling between the
analog and digital sections. It is further recommended to put
digital and analog power traces over the corresponding digital and analog ground traces to minimize noise coupling.
PCB LAYOUT GUIDELINES
This section provides practical guidelines for mixed signal
PCB layout that involves various digital/analog power and
ground traces. Designers should note that these are only
"rule-of-thumb" recommendations and the actual results will
depend heavily on the final layout.
Placement of Digital and Analog Components
GENERAL MIXED SIGNAL LAYOUT
RECOMMENDATION
All digital components and high-speed digital signal traces
should be located as far away as possible from analog
components and circuit traces.
Power and Ground Circuits
For 2 layer mixed signal design, it is important to isolate the
digital power and ground trace paths from the analog power
and ground trace paths. Star trace routing techniques (bringing individual traces back to a central point rather than daisy
chaining traces together in a serial manner) can have a
major impact on low level signal performance. Star trace
routing refers to using individual traces to feed power and
ground to each circuit or even device. This technique will
require a greater amount of design time but will not increase
the final price of the board. The only extra parts required will
be some jumpers.
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Avoiding Typical Design / Layout Problems
Avoid ground loops or running digital and analog traces
parallel to each other (side-by-side) on the same PCB layer.
When traces must cross over each other do it at 90 degrees.
Running digital and analog traces at 90 degrees to each
other from the top to the bottom side as much as possible will
minimize capacitive noise coupling and cross talk.
16
LM4903 1 Watt Audio Power Amplifier
Physical Dimensions
inches (millimeters) unless otherwise noted
MSOP
Order Number LM4903MM
NS Package Number MUA08A
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accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
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Support Center
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Tel: 1-800-272-9959
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Europe Customer Support Center
Fax: +49 (0) 180-530 85 86
Email: [email protected]
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
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.
National Semiconductor
Asia Pacific Customer
Support Center
Fax: +65-6250 4466
Email: [email protected]
Tel: +65-6254 4466
National Semiconductor
Japan Customer Support Center
Fax: 81-3-5639-7507
Email: [email protected]
Tel: 81-3-5639-7560
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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