LM4899 1 Watt Fully Differential Audio Power Amplifier With

LM4899 1 Watt Fully Differential Audio Power Amplifier With
LM4899
1 Watt Fully Differential Audio Power Amplifier With
Shutdown Select and Fixed 6dB Gain
General Description
Key Specifications
The LM4899 is a fully differential 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 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 LM4899 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 LM4899 features a low-power consumption shutdown
mode. To facilitate this, Shutdown may be enabled by either
logic high or low depending on mode selection. Driving the
shutdown mode pin either high or low enables the shutdown
select pin to be driven in a likewise manner to enable Shutdown. Additionally, the LM4899 features an internal thermal
shutdown protection mechanism.
The LM4899 contains advanced pop & click circuitry which
virtually eliminates noises which would otherwise occur during turn-on and turn-off transitions.
The LM4899 has an internally fixed gain of 6dB.
j Improved PSRR at 217Hz
83dB
j Power Output at 5.0V & 1% THD
1.0W(typ.)
j Power Output at 3.3V & 1% THD
400mW(typ.)
j Shutdown Current
0.1µA(typ.)
Features
n Fully differential amplification
n Internal-gain-setting resistors
n Available in space-saving packages micro SMD, MSOP
and LLP
n Ultra low current shutdown mode
n Can drive capacitive loads up to 500pF
n Improved pop & click circuitry which virtually eliminates
noises during turn-on and turn-off transitions
n 2.4 - 5.5V operation
n No output coupling capacitors, snubber networks or
bootstrap capacitors required
n Shutdown high or low selectivity
Applications
n Mobile phones
n PDAs
n Portable electronic devices
Connection Diagrams
9 Bump micro SMD Package
9 Bump micro SMD Marking
200645C7
200645A0
Top View
Order Number LM4899ITL, LM4899ITLX
See NS Package Number TLA09AAA
X - Date Code
T - Die Run Traceability
G - Boomer Family
C1 - LM4899ITL
Boomer ® is a registered trademark of National Semiconductor Corporation.
© 2003 National Semiconductor Corporation
DS200645
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LM4899 1 Watt Fully Differential Audio Power Amplifier With Shutdown Select and Fixed 6dB
Gain
July 2003
LM4899
Connection Diagrams
(Continued)
Mini Small Outline (MSOP) Package
MSOP Marking
20064523
200645C9
Top View
Order Number LM4899MM
See NS Package Number MUB10A
Z - Assembly Code
X - Date Code
TT - Die Run Traceability
G - Boomer Family
B1 - LM4899MM
LD Package
LD Marking
200645C8
Z - Assembly Code
XY - Date Code
TT - Die Run Traceability
L4899 - LM4899LD
20064535
Top View
Order Number LM4899LD
See NS Package Number LDA10B
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LM4899
Typical Application
200645D0
FIGURE 1. Typical Audio Amplifier Application Circuit
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LM4899
Absolute Maximum Ratings
θJA (micro SMD)
(Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
56˚C/W
θJA (MSOP)
190˚C/W
Soldering Information
6.0V
Storage Temperature
220˚C/W
θJC (MSOP)
See AN-1112 "microSMD Wafers Level Chip Scale
Package".
−65˚C to +150˚C
−0.3V to VDD +0.3V
Input Voltage
Power Dissipation (Note 3)
Internally Limited
ESD Susceptibility (Note 4)
2000V
ESD Susceptibility (Note 5)
200V
Junction Temperature
Operating Ratings
Temperature Range
150˚C
TMIN ≤ TA ≤ TMAX
Thermal Resistance
θJC (LD)
12˚C/W
θJA (LD)
63˚C/W
−40˚C ≤ TA ≤ +85˚C
2.4V ≤ VDD ≤ 5.5V
Supply Voltage
Electrical Characteristics VDD = 5V (Notes 1, 2, 8)
The following specifications apply for VDD = 5V and 8Ω load unless otherwise specified. Limits apply for TA = 25˚C.
LM4899
Symbol
Parameter
Conditions
IDD
Quiescent Power Supply Current
VIN = 0V, no Load
VIN = 0V, RL = 8Ω
ISD
Standby Current
VSDMODE = VSHUTDOWN = GND
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
3
5
6
10
mA (max)
0.1
1
µA (max)
THD = 1% (max); f = 1 kHz
Po
Output Power
LM4899LD, RL = 4Ω (Note 11)
LM4899, RL = 8Ω
THD+N
Total Harmonic Distortion+Noise
Po = 0.4 Wrms; f = 1kHz
1.4
1
0.9
0.05
W (min)
%
Vripple = 200mV sine p-p
PSRR
Power Supply Rejection Ratio
CMRR
Common-Mode Rejection Ratio
f = 217Hz (Note 9)
83
f = 1kHz (Note 9)
90
f = 217Hz (Note 10)
83
71
f = 1kHz (Note 10)
83
71
f = 217Hz, VCM = 200mVpp
50
dB
dB (min)
VOS
Output Offset
VIN = 0V
2
mV
VSDIH
Shutdown Voltage Input High
SD Mode = GND
0.9
V
VSDIL
Shutdown Voltage Input Low
SD Mode = GND
0.7
V
VSDIH
Shutdown Voltage Input High
SD Mode = VDD
0.9
V
VSDIL
Shutdown Voltage Input Low
SD Mode = VDD
0.7
V
Electrical Characteristics VDD = 3V (Notes 1, 2, 8)
The following specifications apply for VDD = 3V and 8Ω load unless otherwise specified. Limits apply for TA = 25˚C.
LM4899
Symbol
Parameter
Conditions
Typical
Limit
Units
(Limits)
(Note 6)
(Note 7)
IDD
Quiescent Power Supply Current
VIN = 0V, no Load
VIN = 0V, RL = 8Ω
2.5
4
5.5
9
mA (max)
ISD
Standby Current
VSDMODE = VSHUTDOWN = GND
0.1
1
µA (max)
Po
Output Power
THD = 1% (max); f = 1kHz
LM4899, RL = 8Ω
0.35
W
THD+N
Total Harmonic Distortion+Noise
Po = 0.25Wrms; f = 1kHz
0.3
%
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LM4899
Electrical Characteristics VDD = 3V (Notes 1, 2, 8)
The following specifications apply for VDD = 3V and 8Ω load unless otherwise specified. Limits apply for TA =
25˚C. (Continued)
LM4899
Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Note 7)
Units
(Limits)
Vripple = 200mV sine p-p
PSRR
Power Supply Rejection Ratio
f = 217Hz (Note 9)
83
f = 1kHz (Note 9)
84
f = 217Hz (Note 10)
83
f = 1kHz (Note 10)
83
f = 217Hz, VCM = 200mVpp
50
dB
2
mV
dB
CMRR
Common-Mode Rejection Ratio
VOS
Offset Voltage
VIN = 0V
VSDIH
Shutdown Voltage Input High
SD Mode = GND
0.8
V
VSDIL
Shutdown Voltage Input Low
SD Mode = GND
0.6
V
VSDIH
Shutdown Voltage Input High
SD Mode = VDD
0.8
V
VSDIL
Shutdown Voltage Input Low
SD Mode = VDD
0.6
V
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 LM4899, see power derating
currents 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: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
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: Unterminated input.
Note 10: 10Ω terminated input.
Note 11: : When driving 4Ω loads from a 5V power supply, the LM4899LD must be mounted to a circuit board with the exposed-DAP area soldered down to a 1sq.
in plane of 1oz. copper.
External Components Description
Components
(Figure 1)
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.
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.
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LM4899
Typical Performance Characteristics
LD Specific Characteristics
THD+N vs Frequency
VDD = 5V, RL = 4Ω, PO = 1W
THD+N vs Output Power
VDD = 5V, RL = 4Ω
200645C1
200645B5
LM4899LD
Power Dissipation vs Output Power
LM4899LD
Power Derating Curve
20064511
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20064512
6
LM4899
Typical Performance Characteristics
Non-LD Specific Characteristics
THD+N vs Frequency
VDD = 3V, RL = 8Ω, PO = 275mW
THD+N vs Frequency
VDD = 5V, RL = 8Ω, PO = 400mW
200645B6
200645B4
THD+N vs Frequency
VDD = 2.6V, RL = 8Ω, PO = 150mW
THD+N vs Frequency
VDD = 3V, RL = 4Ω, PO = 225mW
200645B2
200645B3
THD+N vs Output Power
VDD = 5V, RL = 8Ω
THD+N vs Frequency
VDD = 2.6V, RL = 4Ω, PO = 150mW
200645B1
200645C2
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LM4899
Typical Performance Characteristics
Non-LD Specific Characteristics (Continued)
THD+N vs Output Power
VDD = 3V, RL = 8Ω
THD+N vs Output Power
VDD = 3V, RL = 4Ω
200645C0
200645B9
THD+N vs Output Power
VDD = 2.6V, RL = 4Ω
THD+N vs Output Power
VDD = 2.6V, RL = 8Ω
200645B8
200645B7
PSRR vs Frequency
VDD = 3V, RL = 8Ω, Input 10Ω Terminated
PSRR vs Frequency
VDD = 5V, RL = 8Ω, Input 10Ω Terminated
200645B0
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200645A9
8
LM4899
Typical Performance Characteristics
Non-LD Specific Characteristics (Continued)
Output Power vs Supply Voltage
RL = 8Ω
Output Power vs Supply Voltage
RL = 4Ω
200645A6
200645A5
Power Dissipation vs
Output Power
Power Dissipation vs
Output Power
20064581
20064582
Power Dissipation vs
Output Power
Output Power vs
Load Resistance
20064583
20064584
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LM4899
Typical Performance Characteristics
Non-LD Specific Characteristics (Continued)
Supply Current vs Shutdown Voltage
Shutdown Low
Supply Current vs Shutdown Voltage
Shutdown High
20064585
20064586
Clipping (Dropout) Voltage vs
Supply Voltage
Open Loop Frequency Response
20064588
20064587
Noise Floor
Power Derating Curve
20064589
200645A4
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LM4899
Typical Performance Characteristics
Non-LD Specific Characteristics (Continued)
CMRR vs Frequency
VDD = 5V, RL = 8Ω, 200mVpp
CMRR vs Frequency
VDD = 3V, RL = 8Ω, 200mVpp
200645A3
200645A2
PSRR vs Common Mode Voltage
VDD = 3V, RL = 8Ω, 217Hz, 200mVpp
PSRR vs Common Mode Voltage
VDD = 5V
200645A8
200645A7
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LM4899
than two layers. Connect the DAP copper pad to the inner
layer or backside copper heat sink area with 4 (2x2) vias.
The via diameter should be 0.012in - 0.013in with a 0.050in
pitch. Ensure efficient thermal conductivity by platingthrough and solder-filling the vias.
Application Information
DIFFERENTIAL AMPLIFIER EXPLANATION
The LM4899 is a fully differential audio amplifier that features differential input and output stages. Internally this is
accomplished by two circuits: a differential amplifier and a
common mode feedback amplifier that adjusts the output
voltages so that the average value remains VDD/2. The
LM4899 features precisely matched internal gain-setting resistors, thus eliminating the need for external resistors and
fixing the differential gain at AVD = 6dB.
Best thermal performance is achieved with the largest practical copper heat sink area. If the heatsink and amplifier
share the same PCB layer, a nominal 2.5in2 (min) area is
necessary for 5V operation with a 4Ω load. Heatsink areas
not placed on the same PCB layer as the LM4899 should be
5in2 (min) for the same supply voltage and load resistance.
The last two area recommendations apply for 25˚C ambient
temperature. In all circumstances and conditions, the junction temperature must be held below 150˚C to prevent activating the LM4899’s thermal shutdown protection. The
LM4899’s power de-rating curve in the Typical Performance
Characteristics shows the maximum power dissipation versus temperature. Example PCB layouts for the exposedDAP TSSOP and LLP packages are shown in the Demonstration Board Layout section. Further detailed and specific
information concerning PCB layout, fabrication, and mounting an LLP package is available from National Semiconductor’s package Engineering Group under application note AN1187.
A differential amplifier works in a manner where the difference between the two input signals is amplified. In most
applications, this would require input signals that are 180˚
out of phase with each other.
The LM4899 provides what is known as a "bridged mode"
output (bridge-tied-load, BTL). This results in output signals
at Vo1 and Vo2 that are 180˚ out of phase with respect to
each other. Bridged mode operation is different from the
single-ended amplifier configuration that connects the load
between the amplifier output and ground. A bridged amplifier
design has distinct advantages over the single-ended configuration: it provides differential drive to the load, thus doubling maximum possible output swing for a specific supply
voltage. Four times the output power is possible compared
with a single-ended amplifier under the same conditions.
This increase in attainable output power assumes that the
amplifier is not current limited or clipped.
PCB LAYOUT AND SUPPLY REGULATION
CONSIDERATIONS FOR DRIVING 3Ω AND 4Ω LOADS
Power dissipated by a load is a function of the voltage swing
across the load and the load’s impedance. As load impedance decreases, load dissipation becomes increasingly dependent on the interconnect (PCB trace and wire) resistance
between the amplifier output pins and the load’s connections. Residual trace resistance causes a voltage drop,
which results in power dissipated in the trace and not in the
load as desired. For example, 0.1Ω trace resistance reduces
the output power dissipated by a 4Ω load from 1.4W to
1.37W. This problem of decreased load dissipation is exacerbated as load impedance decreases. Therefore, to maintain the highest load dissipation and widest output voltage
swing, PCB traces that connect the output pins to a load
must be as wide as possible.
A bridged configuration, such as the one used in the
LM4899, also creates a second advantage over singleended amplifiers. Since the differential outputs, Vo1 and Vo2,
are biased at half-supply, no net DC voltage exists across
the load. BTL configuration eliminates the output coupling
capacitor required in single-supply, single-ended amplifier
configurations. If an output coupling capacitor is not used in
a single-ended output configuration, the half-supply bias
across the load would result in both increased internal IC
power dissipation as well as permanent loudspeaker damage. Further advantages of bridged mode operation specific
to fully differential amplifiers like the LM4899 include increased power supply rejection ratio, common-mode noise
reduction, and click and pop reduction.
Poor power supply regulation adversely affects maximum
output power. A poorly regulated supply’s output voltage
decreases with increasing load current. Reduced supply
voltage causes decreased headroom, output signal clipping,
and reduced output power. Even with tightly regulated supplies, trace resistance creates the same effects as poor
supply regulation. Therefore, making the power supply
traces as wide as possible helps maintain full output voltage
swing.
EXPOSED-DAP PACKAGE PCB MOUNTING
CONSIDERATIONS
The LM4899’s exposed-DAP (die attach paddle) package
(LD) provide a low thermal resistance between the die and
the PCB to which the part is mounted and soldered. This
allows rapid heat transfer from the die to the surrounding
PCB copper traces, ground plane and, finally, surrounding
air. The result is a low voltage audio power amplifier that
produces 1.4W at ≤ 1% THD with a 4Ω load. This high power
is achieved through careful consideration of necessary thermal design. Failing to optimize thermal design may compromise the LM4899’s high power performance and activate
unwanted, though necessary, thermal shutdown protection.
The LD package must have its DAP soldered to a copper
pad on the PCB. The DAP’s PCB copper pad is connected to
a large plane of continuous unbroken copper. This plane
forms a thermal mass and heat sink and radiation area.
Place the heat sink area on either outside plane in the case
of a two-sided PCB, or on an inner layer of a board with more
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POWER DISSIPATION
Power dissipation is a major concern when designing a
successful amplifer, whether the amplifier is bridged or
single-ended. Equation 2 states the maximum power dissipation point for a single-ended amplifier operating at a given
supply voltage and driving a specified output load.
PDMAX = (VDD)2 / (2π2RL) Single-Ended
12
(1)
bypass and power supply pins should be as close to the
device as possible. A larger half-supply bypass capacitor
improves PSRR because it increases half-supply stability.
Typical applications employ a 5V regulator with 10µF and
0.1µF bypass capacitors that increase supply stability. This,
however, does not eliminate the need for bypassing the
supply nodes of the LM4899. Although the LM4899 will
operate without the bypass capacitor CB, although the PSRR
may decrease. A 1µF capacitor is recommended for CB. This
value maximizes PSRR performance. Lesser values may be
used, but PSRR decreases at frequencies below 1kHz. The
issue of CB selection is thus dependant upon desired PSRR
and click and pop performance.
(Continued)
However, a direct consequence of the increased power delivered to the load by a bridge amplifier is an increase in
internal power dissipation versus a single-ended amplifier
operating at the same conditions.
PDMAX = 4*(VDD)2 / (2π2RL) Bridge Mode
(2)
Since the LM4899 has bridged outputs, the maximum internal power dissipation is 4 times that of a single-ended amplifier. Even with this substantial increase in power dissipation, the LM4899 does not require additional heatsinking
under most operating conditions and output loading. From
Equation 3, assuming a 5V power supply and an 8Ω load,
the maximum power dissipation point is 625mW. The maximum power dissipation point obtained from Equation 3 must
not be greater than the power dissipation results from Equation 4:
PDMAX = (TJMAX - TA) / θJA
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4899 contains shutdown circuitry that is used to turn off
the amplifier’s bias circuitry. In addition, the LM4899 contains a Shutdown Mode pin, allowing the designer to designate whether the part will be driven into shutdown with a high
level logic signal or a low level logic signal. This allows the
designer maximum flexibility in device use, as the Shutdown
Mode pin may simply be tied permanently to either VDD or
GND to set the LM4899 as either a "shutdown-high" device
or a "shutdown-low" device, respectively. The device may
then be placed into shutdown mode by toggling the Shutdown Select pin to the same state as the Shutdown Mode
pin. For simplicity’s sake, this is called "shutdown same", as
the LM4899 enters shutdown mode 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 Supply Current vs Shutdown 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.
(3)
The LM4899’s θJA in an MUA10A package is 190˚C/W.
Depending on the ambient temperature, TA, of the system
surroundings, Equation 4 can be used to find the maximum
internal power dissipation supported by the IC packaging. If
the result of Equation 3 is greater than that of Equation 4,
then either the supply voltage must be decreased, the load
impedance increased, the ambient temperature reduced, or
the θJA reduced with heatsinking. In many cases, larger
traces near the output, VDD, and GND pins can be used to
lower the θJA. The larger areas of copper provide a form of
heatsinking allowing higher power dissipation. For the typical
application of a 5V power supply, with an 8Ω load, the
maximum ambient temperature possible without violating the
maximum junction temperature is approximately 30˚C provided that device operation is around the maximum power
dissipation point. Recall that internal power dissipation is a
function of output power. If typical operation is not around the
maximum power dissipation point, the LM4899 can operate
at higher ambient temperatures. Refer to the Typical Performance Characteristics curves for power dissipation information.
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 (or pull-down, depending on shutdown high or low application). This scheme guarantees that
the shutdown pin will not float, thus preventing unwanted
state changes.
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 location on both the
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LM4899
Application Information
LM4899
Physical Dimensions
inches (millimeters)
unless otherwise noted
9-Bump micro SMD
Order Number LM4899ITL
NS Package Number TLA09AAA
X1 = 1.514 ± 0.03 X2 = 1.514 ± 0.03 X3 = 0.600 ± 0.075
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LM4899
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
LLP
Order Number LM4899LD
NSPackage Number LDA10B
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LM4899 1 Watt Fully Differential Audio Power Amplifier With Shutdown Select and Fixed 6dB
Gain
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
Mini Small Outline (MSOP)
Order Number LM4899MM
NSPackage Number MUB10A
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.
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Americas Customer
Support Center
Email: [email protected]
Tel: 1-800-272-9959
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Fax: +49 (0) 180-530 85 86
Email: [email protected]
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2. A critical component is any component of a life
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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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