LM4879
LM4879 1.1 Watt Audio Power Amplifier
Literature Number: SNAS142F
LM4879
1.1 Watt Audio Power Amplifier
General Description
The LM4879 is an audio power amplifier primarily designed
for demanding applications in mobile phones and other por-
table communication device applications. It is capable of
delivering 1.1 watt of continuous average power to an 8Ω
BTL load with less than 1% distortion (THD+N) from a 5V
DC
power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. The LM4879 does not require output
coupling capacitors or bootstrap capacitors, and therefore is
ideally suited for lower-power portable applications where
minimal space and power consumption are primary require-
ments.
The LM4879 features a low-power consumption global shut-
down mode, which is achieved by driving the shutdown pin
with logic low. Additionally, the LM4879 features an internal
thermal shutdown protection mechanism.
The LM4879 contains advanced pop & click circuitry which
eliminates noises which would otherwise occur during
turn-on and turn-off transitions.
The LM4879 is unity-gain stable and can be configured by
external gain-setting resistors.
Key Specifications
jPSRR: 5V, 3V @217Hz 62dB (typ)
jPower Output at 5V & 1% THD+N 1.1W (typ)
jPower Output at 3V & 1% THD+N 350mW (typ)
jShutdown Current 0.1µA (typ)
Features
nNo output coupling capacitors, snubber networks or
bootstrap capacitors required
nUnity gain stable
nUltra low current shutdown mode
nFast turn on: 80ms (typ), 110ms (max) with 1.0µF
capacitor
nBTL output can drive capacitive loads up to 100pF
nAdvanced pop & click circuitry eliminates noises during
turn-on and turn-off transitions
n2.2V - 5.0V operation
nAvailable in space-saving µSMD, LLP, and MSOP
packages
Applications
nMobile Phones
nPDAs
nPortable electronic devices
Typical Application
Boomer®is a registered trademark of National Semiconductor Corporation.
20024301
FIGURE 1. Typical Audio Amplifier Application Circuit
October 2004
LM4879 1.1 Watt Audio Power Amplifier
© 2004 National Semiconductor Corporation DS200243 www.national.com
Connection Diagrams
8 Bump micro SMD 8 Bump micro SMD Marking
20024382
Top View
Order Number LM4879IBP, LM4879IBPX
See NS Package Number BPA08DDB
20024383
Top View
X - Date Code
T - Die Traceability
G - Boomer Family
N- LM4879IBP
Mini Small Outline (MSOP) Package MSOP Marking
20024384
Top View
NC = No Connect
Order Number LM4879MM
See NS Package Number MUB10A
20024385
Top View
G - Boomer Family
79-LM4879MM
9 Bump micro SMD 9 Bump micro SMD Marking
20024386
Top View
Order Number LM4879IBL, LM4879IBLX
See NS package Number BLA09AAB
20024387
Top View
X - Date Code
T - Die Traceability
G - Boomer Family
79 - LM4879IBL
LM4879
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Connection Diagrams (Continued)
9 Bump micro SMD 9 Bump micro SMD Marking
20024386
Top View
Order Number LM4879ITL, LM4879ITLX
See NS package Number TLA09AAA
200243B3
Top View
X - Date Code
T - Die Traceability
G - Boomer Family
B3 - LM4879ITL
Leadless Leadframe Package (LLP) LLP Marking
20024302
Top View
Order Number LM4879SD
See NS Package Number SDC08A
200243B6
Top View
N - NS Logo
U - Fab Code
Z - Assembly Plant Code
XY - Date Code
TT - Die Traceability
L4879SD - LM4879SD
LM4879
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Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (Note 9) 6.0V
Storage Temperature −65˚C to +150˚C
Input Voltage −0.3V to V
DD
+0.3V
Power Dissipation (Note 3) Internally Limited
ESD Susceptibility (Note 4) 2000V
ESD Susceptibility (Note 5) 200V
Junction Temperature 150˚C
Thermal Resistance
θ
JA
(BPA08DDB) 220˚C/W (Note 10)
θ
JA
(SDC08A) 64˚C/W (Note 12)
θ
JA
(TLA09AAA) 180˚C/W (Note 10)
θ
JA
(BLA09AAB) 180˚C/W (Note 10)
θ
JC
(MUB10A) 56˚C/W
θ
JA
(MUB10A) 190˚C/W
Operating Ratings
Temperature Range
T
MIN
≤T
A
≤T
MAX
−40˚C ≤T
A
≤85˚C
Supply Voltage 2.2V ≤V
DD
≤5.5V
Electrical Characteristics V
DD
=5V (Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for T
A
= 25˚C.
Symbol Parameter Conditions
LM4879 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
I
DD
Quiescent Power Supply Current V
IN
= 0V, 8ΩBTL 5 10 mA (max)
I
SD
Shutdown Current V
shutdown
= GND 0.1 2.0 µA (max)
V
OS
Output Offset Voltage 5 40 mV (max)
P
o
Output Power THD+N = 1% (max); f = 1kHz 1.1 0.9 W (min)
THD+N Total Harmonic Distortion+Noise P
o
= 0.4Wrms; f = 1kHz 0.1 %
PSRR Power Supply Rejection Ratio
V
ripple
= 200mVsine p-p, C
B
=
1.0µF
Input terminated with 10Ωto
ground
68 (f = 1kHz)
62 (f =
217Hz) 55 dB (min)
V
SDIH
Shutdown High Input Voltage 1.4 V (min)
V
SDIL
Shutdown Low Input Voltage 0.4 V (max)
T
WU
Wake-up Time C
B
= 1.0µF 80 110 ms (max)
N
OUT
Output Noise
A-Weighted; Measured across 8Ω
BTL
Input terminated with 10Ωto
ground
26 µV
RMS
Electrical Characteristics V
DD
= 3.0V (Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for T
A
= 25˚C.
Symbol Parameter Conditions
LM4879 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
I
DD
Quiescent Power Supply Current V
IN
= 0V, 8ΩBTL 4.5 9 mA (max)
I
SD
Shutdown Current V
shutdown
= GND 0.1 2.0 µA (max)
V
OS
Output Offset Voltage 5 40 mV (max)
P
o
Output Power THD+N = 1% (max); f = 1kHz 350 320 mW
THD+N Total Harmonic Distortion+Noise P
o
= 0.15Wrms; f = 1kHz 0.1 %
PSRR Power Supply Rejection Ratio
V
ripple
= 200mVsine p-p, C
B
=
1.0µF
Input terminated with 10Ωto
ground
68 (f = 1kHz)
62 (f =
217Hz) 55 dB (min)
V
SDIH
Shutdown High Input Voltage 1.4 V (min)
V
SDIL
Shutdown Low Input Voltage 0.4 V (max)
T
WU
Wake-up Time C
B
= 1.0µF 80 110 ms (max)
LM4879
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Electrical Characteristics V
DD
= 3.0V (Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for T
A
=
25˚C. (Continued)
Symbol Parameter Conditions
LM4879 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
N
OUT
Output Noise
A-Weighted; Measured across 8Ω
BTL
Input terminated with 10Ωto
ground
26 µV
RMS
Electrical Characteristics V
DD
= 2.6V (Notes 1, 2)
The following specifications apply for the circuit shown in Figure 1 unless otherwise specified. Limits apply for T
A
= 25˚C.
Symbol Parameter Conditions
LM4879 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
I
DD
Quiescent Power Supply Current V
IN
= 0V, 8ΩBTL 3.5 mA
I
SD
Shutdown Current V
shutdown
= GND 0.1 µA
V
OS
Output Offset Voltage 5 mV
P
o
Output Power
THD+N = 1% (max); f = 1kHz
R
L
=8Ω250 mW
R
L
=4Ω350
THD+N Total Harmonic Distortion+Noise P
o
= 0.1Wrms; f = 1kHz 0.1 %
PSRR Power Supply Rejection Ratio
V
ripple
= 200mVsine p-p, C
B
=
1.0µF
Input terminated with 10Ωto
ground
55 (f = 1kHz)
55 (f =
217Hz) dB
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 =(T
JMAX–TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4879, see power derating
curves for additional information.
Note 4: Human body model, 100pF discharged through a 1.5kΩresistor.
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: For micro SMD only, shutdown current is measured in a Normal Room Environment. Exposure to direct sunlight will increase ISD by a maximum of 2µA.
Note 9: 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 part will be protected. If the part is enabled when VDD is above 6V, circuit performance will
be curtailed or the part may be permanently damaged.
Note 10: All bumps have the same thermal resistance and contribute equally when used to lower thermal resistance.
Note 11: Maximum power dissipation (PDMAX) in the device occurs at an output power level significantly below full output power. PDMAX can be calculated using
Equation 1 shown in the Application section. It may also be obtained from the power dissipation graphs.
Note 12: The stated θJA is achieved when the LLP package’s DAP is soldered to a 4in2copper heatsink plain.
LM4879
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External Components Description
(Figure 1)
Components Functional Description
1. R
i
Inverting input resistance which sets the closed-loop gain in conjunction with R
f
. This resistor also forms a
high pass filter with C
i
at f
C
= 1/(2πR
i
C
i
).
2. C
i
Input coupling capacitor which blocks the DC voltage at the amplifiers input terminals. Also creates a
highpass filter with R
i
at f
c
= 1/(2πR
i
C
i
). Refer to the section, Proper Selection of External Components,
for an explanation of how to determine the value of C
i
.
3. R
f
Feedback resistance which sets the closed-loop gain in conjunction with R
i
.
4. C
S
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. C
B
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 C
B
.
LM4879
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Typical Performance Characteristics
THD+N vs Frequency
V
DD
= 5V, R
L
=8Ω, PWR = 250mW
THD+N vs Frequency
V
DD
= 3V, R
L
=8Ω, PWR = 150mW
20024337 20024338
THD+N vs Frequency
V
DD
= 2.6V, R
L
=8Ω, PWR = 100mW
THD+N vs Frequency
V
DD
= 2.6V, R
L
=4Ω, PWR = 100mW
20024339 20024340
THD+N vs Power Out
V
DD
= 5V, R
L
=8Ω, f = 1kHz
THD+N vs Power Out
V
DD
= 3V, R
L
=8Ω, f = 1kHz
20024341 20024342
LM4879
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Typical Performance Characteristics (Continued)
THD+N vs Power Out
V
DD
= 2.6V, R
L
=8Ω, f = 1kHz
THD+N vs Power Out
V
DD
= 2.6V, R
L
=4Ω, f = 1kHz
20024343 20024344
Power Supply Rejection Ratio
V
DD
=5V
Power Supply Rejection Ratio
V
DD
=3V
20024345 20024373
Power Supply Rejection Ratio
V
DD
= 2.6V
Power Dissipation vs Output Power
V
DD
=5V
20024347
20024346
LM4879
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Typical Performance Characteristics (Continued)
Power Dissipation
vs Output Power
V
DD
=3V
Power Dissipation
vs Output Power
V
DD
= 2.6V
20024349 20024348
Power Dissipation
vs Output Power (LLP Package)
V
DD
=5V
Power Derating - MSOP
P
DMAX
= 670mW
V
DD
= 5V, R
L
=8Ω
20024313
20024379
Power Derating - 8 Bump µSMD
P
DMAX
= 670mW
V
DD
= 5V, R
L
=8Ω
Power Derating - 9 Bump µSMD
P
DMAX
= 670mW
V
DD
= 5V, R
L
=8Ω
20024380 20024381
LM4879
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Typical Performance Characteristics (Continued)
Power Derating - LLP
P
DMAX
= 670mV
V
DD
= 5V, R
L
=8
Output Power
vs Supply Voltage
200243B4
20024351
Output Power
vs Supply Voltage
Output Power
vs Load Resistance
20024350 20024374
Clipping (Dropout) Voltage
vs Supply Voltage
Supply Current
Shutdown Voltage
20024352 20024375
LM4879
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Typical Performance Characteristics (Continued)
Shutdown Hysterisis Voltage
V
DD
=5V
Shutdown Hysterisis Voltage
V
DD
=3V
20024376 20024377
Shutdown Hysterisis Voltage
V
DD
= 2.6V
Open Loop
Frequency Response
20024378 20024354
Frequency Response
vs Input Capacitor Size
20024356
LM4879
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Application Information
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4879 has two operational
amplifiers internally, allowing for a few different amplifier
configurations. The first amplifier’s gain is externally config-
urable, 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 R
f
to R
i
while
the second amplifier’s gain is fixed by the two internal 20 kΩ
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
A
VD
= 2 *(R
f
/R
i
)
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 configura-
tion 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 con-
ditions. 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 ex-
cessive clipping, please refer to the Audio Power Amplifier
Design section.
A bridge configuration, such as the one used in LM4879,
also creates a second advantage over single-ended amplifi-
ers. 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 configura-
tion. 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.
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 LM4879 has two opera-
tional 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 Equa-
tion 1.
P
DMAX
= 4*(V
DD
)
2
/(2π
2
R
L
) (1)
It is critical that the maximum junction temperature (T
JMAX
)
of 150˚C is not exceeded. T
JMAX
can be determined from the
power derating curves by using P
DMAX
and the PC board foil
area. By adding additional copper foil, the thermal resistance
of the application can be reduced from a free air value of
150˚C/W, resulting in higher P
DMAX
. Additional copper foil
can be added to any of the leads connected to the LM4879.
It is especially effective when connected to V
DD
, GND, and
the output pins. Refer to the application information on the
LM4879 reference design board for an example of good heat
sinking. If T
JMAX
still exceeds 150˚C, then additional
changes must be made. These changes can include re-
duced supply voltage, higher load impedance, or reduced
ambient temperature. Internal power dissipation is a function
of output power. Refer to the Typical Performance Charac-
teristics curves for power dissipation information for differ-
ent output powers and output loading.
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 appli-
cations employ a 5V regulator with 10 µF tantalum or elec-
trolytic capacitor and a ceramic bypass capacitor which aid
in supply stability. This does not eliminate the need for
bypassing the supply nodes of the LM4879. The selection of
a bypass capacitor, especially C
B
, is dependent upon PSRR
requirements, click and pop performance (as explained in
the section, Proper Selection of External Components),
system cost, and size constraints.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4879 contains a shutdown pin to externally turn off the
amplifier’s bias circuitry. This shutdown feature turns the
amplifier off when a logic low is placed on the shutdown pin.
By switching the shutdown pin to ground, the LM4879 supply
current draw will be minimized in idle mode. While the device
will be disabled with shutdown pin voltages less than
0.4V
DC
, the idle current may be greater than the typical
value of 0.1µA. (Idle current is measured with the shutdown
pin tied to ground).
In many applications, a microcontroller or microprocessor
output is used to control the shutdown circuitry to provide a
quick, smooth transition into shutdown. Another solution is to
use a single-pole, single-throw switch in conjunction with an
external pull-up resistor. When the switch is closed, the
shutdown pin is connected to ground which disables the
amplifier. If the switch is open, then the external pull-up
resistor to V
DD
will enable the LM4879. This scheme guar-
antees that the shutdown pin will not float thus preventing
unwanted state changes.
PROPER SELECTION OF EXTERNAL COMPONENTS
Proper selection of external components in applications us-
ing integrated power amplifiers is critical to optimize device
and system performance. While the LM4879 is tolerant of
external component combinations, consideration to compo-
nent values must be used to maximize overall system qual-
ity.
The LM4879 is unity-gain stable which gives the designer
maximum system flexibility. The LM4879 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
from sources such as audio codecs. Please refer to the
section, Audio Power Amplifier Design, for a more com-
plete explanation of proper gain selection.
Besides gain, one of the major considerations is the closed-
loop bandwidth of the amplifier. To a large extent, the band-
width is dictated by the choice of external components
shown in Figure 1. The input coupling capacitor, C
i
, forms a
first order high pass filter which limits low frequency re-
sponse. This value should be chosen based on needed
frequency response for a few distinct reasons.
LM4879
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Application Information (Continued)
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 attenu-
ation. But in many cases the speakers used in portable
systems, whether internal or external, have little ability to
reproduce signals below 100 Hz to 150 Hz. Thus, using a
large input capacitor may not increase actual system perfor-
mance.
In addition to system cost and size, click and pop perfor-
mance is effected by the size of the input coupling capacitor,
C
i.
A larger input coupling capacitor requires more charge to
reach its quiescent DC voltage (nominally 1/2 V
DD
). 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 consid-
eration should be paid to the bypass capacitor value. Bypass
capacitor, C
B
, is the most critical component to minimize
turn-on pops since it determines how fast the LM4879 turns
on. The slower the LM4879’s outputs ramp to their quiescent
DC voltage (nominally 1/2 V
DD
), the smaller the turn-on pop.
Choosing C
B
equal to 1.0 µF along with a small value of C
i
(in the range of 0.1 µF to 0.39 µF), should produce a virtually
clickless and popless shutdown function. While the device
will function properly, (no oscillations or motorboating), with
C
B
equal to 0.1 µF, the device will be much more susceptible
to turn-on clicks and pops. Thus, a value of C
B
equal to
1.0 µF is recommended in all but the most cost sensitive
designs.
AUDIO POWER AMPLIFIER DESIGN
A 1W/8ΩAudio Amplifier
Given:
Power Output 1 Wrms
Load Impedance 8Ω
Input Level 1 Vrms
Input Impedance 20 kΩ
Bandwidth 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
Output Power vs Supply Voltage graphs in the Typical Per-
formance Characteristics section, the supply rail can be
easily found. A second way to determine the minimum sup-
ply rail is to calculate the required V
opeak
using Equation 2
and add the output voltage. Using this method, the minimum
supply voltage would be (V
opeak
+(V
OD
TOP +V
OD
BOT)), where
V
OD
BOT and V
OD
TOP are extrapolated from the Dropout Volt-
age vs Supply Voltage curve in the Typical Performance
Characteristics section.
(2)
5V is a standard voltage, in most applications, chosen for the
supply rail. Extra supply voltage creates headroom that al-
lows the LM4879 to reproduce peaks in excess of 1W with-
out 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 Equa-
tion 3.
(3)
A
VD
=(R
f
/R
i
)2
From Equation 3, the minimum A
VD
is 2.83; use A
VD
=3.
Since the desired input impedance was 20 kΩ, and with a
A
VD
of 3, a ratio of 1.5:1 of R
f
to R
i
results in an allocation of
R
i
=20kΩand R
f
=30kΩ. The final design step is to
address the bandwidth requirements which must be stated
as a pair of −3 dB frequency points. Five times away from a
−3 dB point is 0.17 dB down from passband response which
is better than the required ±0.25 dB specified.
f
L
= 100 Hz/5 = 20 Hz
f
H
=20kHz*5=100kHz
As stated in the External Components section, R
i
in con-
junction with C
i
create a highpass filter.
C
i
≥1/(2π*20 kΩ*20 Hz) = 0.397 µF; use 0.39 µF
The high frequency pole is determined by the product of the
desired frequency pole, f
H
, and the differential gain, A
VD
.
With a A
VD
= 3 and f
H
= 100 kHz, the resulting GBWP =
300 kHz which is much smaller than the LM4879 GBWP of
10 MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4879 can still be used without running into bandwidth
limitations.
LM4879
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Application Information (Continued)
The LM4879 is unity-gain stable and requires no external
components besides gain-setting resistors, an input coupling
capacitor, and proper supply bypassing in the typical appli-
cation. 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 elimi-
nates possible high frequency oscillations. Care should be
taken when calculating the -3dB frequency in that an incor-
rect combination of R
3
and C
4
will cause rolloff before
20kHz. A typical combination of feedback resistor and ca-
pacitor that will not produce audio band high frequency rolloff
is R
3
= 20kΩand C
4
= 25pf. These components result in a
-3dB point of approximately 320 kHz.
20024388
FIGURE 2. HIGHER GAIN AUDIO AMPLIFIER
LM4879
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Application Information (Continued)
20024389
FIGURE 3. DIFFERENTIAL AMPLIFIER CONFIGURATION FOR LM4879
20024390
FIGURE 4. REFERENCE DESIGN BOARD and LAYOUT - micro SMD
LM4879
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Application Information (Continued)
20024368
FIGURE 5. REFERENCE DESIGN BOARD and PCB LAYOUT GUIDELINES - MSOP & SO Boards
LM4879
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Application Information (Continued)
LM4879 micro SMD BOARD ARTWORK
Silk Screen Top Layer
20024357
20024358
Bottom Layer Inner Layer Ground
20024359 20024360
Inner Layer V
DD
20024361
LM4879
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Application Information (Continued)
LM4879 MSOP DEMO BOARD ARTWORK
Silk Screen Top Layer
20024365
20024366
Bottom Layer
20024367
TABLE 1. Mono LM4879 Reference Design Boards Bill of Material for all 3 Demo Boards
Item Part Number Part Description Qty Ref Designator
1 551011208-001 LM4879 Mono Reference Design Board 1
10 482911183-001 LM4879 Audio AMP 1 U1
20 151911207-001 Tant Cap 1uF 16V 10 1 C1
21 151911207-002 Cer Cap 0.39uF 50V Z5U 20% 1210 1 C2
25 152911207-001 Tant Cap 1.0uF 16V 10 1 C3
30 472911207-001 Res 20K Ohm 1/10W 5 3 R1, R2, R3
35 210007039-002 Jumper Header Vertical Mount 2X1 0.100 2 J1, J2
LM4879
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Application Information (Continued)
LM4879 LLP DEMO BOARD ARTWORK
Silk Screen Top Layer
200243C2 200243C0
Bottom Layer
200243C1
LM4879
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Application Information (Continued)
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.
General Mixed Signal Layout Recommendation
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 (bring-
ing 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
take require a greater amount of design time but will not
increase the final price of the board. The only extra parts
required may be some jumpers.
Single-Point Power / Ground Connections
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 digi-
tal and analog ground traces to minimize noise coupling.
Placement of Digital and Analog Components
All digital components and high-speed digital signals traces
should be located as far away as possible from analog
components and circuit traces.
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.
LM4879
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Physical Dimensions inches (millimeters) unless otherwise noted
Note: Unless otherwise specified.
1. Epoxy coating.
2. 63Sn/37Pb eutectic bump.
3. Recommend non-solder mask defined landing pad.
4. Pin 1 is established by lower left corner with respect to text orientation pins are numbered counterclockwise.
5. Reference JEDEC registration MO-211, variation BC.
8-Bump micro SMD
Order Number LM4879IBP, LM4879IBPX
NS Package Number BPA08DDB
X1 = 1.361±0.03 X2 = 1.361±0.03 X3 = 0.850±0.10
LM4879
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Note: Unless otherwise specified.
1. Epoxy coating.
2. 63Sn/37Pb eutectic bump.
3. Recommend non-solder mask defined landing pad.
4. Pin 1 is established by lower left corner with respect to text orientation pins are numbered counterclockwise.
5. Reference JEDEC registration MO-211, variation BC.
9-Bump micro SMD
Order Number LM4879IBL, LM4879IBLX
NS Package Number BLA09AAB
X1 = 1.514±0.03 X2 = 1.514±0.03 X3 = 0.945±0.10
LM4879
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LLP
Order Number LM4879SD
NS Package Number SDC08A
LM4879
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
9-Bump micro SMD
Order Number LM4879ITL LM4879ITLX
NS Package Number TLA09AAA
X1 = 1.514±0.03 X2 = 1.514±0.03 X3 = 0.60±0.075
MSOP
Order Number LM4879MM
NS Package Number MUB10A
LM4879
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Notes
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
LIFE SUPPORT POLICY
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 Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship
Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned
Substances’’ as defined in CSP-9-111S2.
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Support Center
Email: new.feedback@nsc.com
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Email: europe.support@nsc.com
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www.national.com
LM4879 1.1 Watt Audio Power Amplifier
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