LM4863
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LM4863
Dual 2.2W Audio Amplifier Plus Stereo
Headphone Function
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FEATURES
APPLICATIONS
•
•
•
•
•
•
•
•
1
2
Stereo Headphone Amplifier Mode
“Click and Pop” Suppression Circuitry
Unity-Gain Stable
Thermal Shutdown Protection Circuitry
SOIC, TSSOP, exposed-DAP TSSOP, and
WQFN packages
KEY SPECIFICATIONS
•
•
•
•
PO at 1% THD+N
– LM4863LQ, 3Ω, 4Ω loads: 2.5W(typ),
2.2W(typ)
– LM4863MTE, 3Ω, 4Ω loads: 2.5W(typ),
2.2W(typ)
– LM4863MTE, 8Ω load: 1.1W(typ)
– LM4863, 8Ω: 1.1W(typ)
Single-ended mode THD+N at 75mW into 32Ω:
0.5%(max)
Shutdown current: 0.7μA(typ)
Supply voltage range: 2.0V to 5.5V
Multimedia Monitors
Portable and Desktop Computers
Portable Televisions
DESCRIPTION
The LM4863 is a dual bridge-connected audio power
amplifier which, when connected to a 5V supply, will
deliver 2.2W to a 4Ω load or 2.5W to a 3Ω load with
less than 1.0% THD+N (see Notes below). In
addition, the headphone input pin allows the
amplifiers to operate in single-ended mode when
driving stereo headphones.
Boomer audio power amplifiers were designed
specifically to provide high quality output power from
a surface mount package while requiring few external
components. To simplify audio system design, the
LM4863 combines dual bridge speaker amplifiers and
stereo headphone amplifiers on one chip.
The LM4863 features an externally controlled, lowpower consumption shutdown mode, a stereo
headphone amplifier mode, and thermal shutdown
protection. It also utilizes circuitry to reduce “clicks
and pops” during device turn-on.
.
NOTE
An LM4863MTE or LM4863LQ that has been properly mounted to a circuit board will
deliver 2.2W into 4Ω. The other package options for the LM4863 will deliver 1.1W into 8Ω.
See Application Information for further information concerning the LM4863MTE and
LM4863LQ.
NOTE
An LM4863MTE or LM4863LQ that has been properly mounted to a circuit board and
forced-air cooled will deliver 2.5W into 3Ω.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1999–2013, Texas Instruments Incorporated
LM4863
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Typical Application
Note: Pin out shown for SOIC package. Refer to Connection Diagrams for the pinout of the TSSOP, Exposed-DAP
TSSOP, and Exposed-DAP WQFN packages.
Connection Diagrams
Figure 1. 16-Pin SOIC - Top View
See Package Number DW0016B
2
Figure 2. 20-Pin TSSOP - Top View
See Package Number PW0020A
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Figure 3. 20-Pin Exposed-DAP TSSOP - Top View
See Package Number PWP0020A
Figure 4. 24-Pin Exposed-DAP WQFN - Top View
See Package Number NHW0024A
Not recommended for new designs. Contact TI Audio Marketing.
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings
(1) (2) (2)
Supply Voltage
6.0V
−65°C to +150°C
Storage Temperature
−0.3V to VDD +0.3V
Input Voltage
(3)
Internally limited
ESD Susceptibility (4)
2000V
Power Dissipation
ESD Susceptibility
(5)
200V
Junction Temperature
Solder Information
Thermal Resistance
150°C
Small Outline Package
Vapor Phase (60 sec.)
215°C
Infrared (15 sec.)
220°C
θJC (typ)—DW0016B
20°C/W
θJA (typ)—DW0016B
80°C/W
θJC (typ)—DW0020A
20°C/W
θJA (typ)—DW0020A
80°C/W
θJC (typ)—PWP0020A
2°C/W
θJA (typ)—PWP0020A
41°C/W
(6)
θJA (typ)—PWP0020A
51°C/W
(7)
90°C/W (8)
θJA (typ)—PWP0020A
θJC (typ)—NHW0024A
3.0°C/W
θJA (typ)—NHW0024A
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
42°C/W
(9)
Not recommended for new designs. Contact Texas Insturments Audio Marketing.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
The maximum power dissipation is dictated by TJMAX, θ JA, and the ambient temperature TA and must be derated at elevated
temperatures. The maximum allowable power dissipation is PDMAX = (TJMAX − T A)/θJA. For the LM4863, TJMAX = 150°C. For the θJAs for
different packages, please see Application Informationor the Absolute Maximum Ratings section.
Human body model, 100 pF discharged through a 1.5kΩ resistor.
Machine model, 220pF – 240pF discharged through all pins.
The given θJA is for an LM4863 packaged in an PWP0020A with the exposed−DAP soldered to an exposed 2in2 area of 1oz printed
circuit board copper.
The given θJA is for an LM4863 packaged in an PWP0020A with the exposed−DAP soldered to an exposed 1in2 area of 1oz printed
circuit board copper.
The given θJA is for an LM4863 packaged in an PWP0020A with the exposed-DAP not soldered to printed circuit board copper.
The given θJA is for an LM4863 packaged in an NHW0024A with the exposed−DAP soldered to an exposed 2in2 area of 1oz printed
circuit board copper.
Operating Ratings
Temperature Range
TMIN ≤ TA ≤ TMAX
4
−40°C ≤ TA ≤ 85°C
2.0V ≤ VDD ≤ 5.5V
Supply Voltage
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Electrical Characteristics for Entire IC
(1) (2)
The following specifications apply for VDD= 5V unless otherwise noted. Limits apply for TA= 25°C.
Symbol
Parameter
Conditions
LM4863
Typical
VDD
(3)
Limit
Supply Voltage
IDD
Quiescent Power Supply Current
VIN = 0V, IO = 0A
(5)
, HP-IN = 0V
11.5
VIN = 0V, IO = 0A
(5)
, HP-IN = 4V
5.8
Units
(Limits)
2
V (min)
5.5
V (max)
20
mA (max)
6
mA (min)
2
μA (max)
mA
ISD
Shutdown Current
VIH
Headphone High Input Voltage
4
V (min)
VIL
Headphone Low Input Voltage
0.8
V (max)
(1)
(2)
(3)
(4)
(5)
VDD applied to the SHUTDOWN pin
(4)
0.7
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 specify specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the
Operating Ratings. Specifications are not specified for parameters where no limit is given, however, the typical value is a good indication
of device performance.
All voltages are measured with respect to the ground (GND) pins unless otherwise specified.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to TI's AOQL (Average Outgoing Quality Level).
The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier.
Electrical Characteristics for Bridged-Mode Operation
(1) (2)
The following specifications apply for VDD= 5V unless otherwise specified. Limits apply for TA= 25°C.
Symbol
Parameter
Conditions
LM4863
Typical
VOS
Output Offset Voltage
PO
Output Power
(5)
VIN = 0V
(3)
5
Limit
50
(4)
Units
(Limits)
mV (max)
(6)
THD+N = 1%, f = 1kHz
LM4863MTE, RL = 3Ω
LM4863LQ, RL = 3Ω
2.5
2.5
W
W
LM4863MTE, RL = 4Ω
LM4863LQ, RL = 4Ω
2.2
2.2
W
W
LM4863, RL = 8Ω
1.1
THD+N = 10%, f = 1kHz
1.0
W (min)
(6)
LM4863MTE, RL = 3Ω
LM4863LQ, RL = 3Ω
3.2
3.2
W
W
LM4863MTE, RL = 4Ω
LM4863LQ, RL = 4Ω
2.7
2.7
W
W
LM4863, RL = 8Ω
THD+N = 1%, f = 1kHz, RL = 32Ω
1.5
W
0.34
W
%
THD+N
Total Harmonic Distortion+Noise
20Hz ≤ f ≤ 20kHz, AVD = 2
LM4863MTE, RL = 4Ω, PO = 2W
LM4863LQ, RL = 4Ω, PO = 2W
0.3 0.3
LM4863, RL = 8Ω, PO = 1W
0.3
%
PSRR
Power Supply Rejection Ratio
VDD = 5V, VRIPPLE = 200mVRMS, RL = 8Ω,
CB = 1.0μF
67
dB
(1)
(2)
(3)
(4)
(5)
(6)
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 specify specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the
Operating Ratings. Specifications are not specified for parameters where no limit is given, however, the typical value is a good indication
of device performance.
All voltages are measured with respect to the ground (GND) pins unless otherwise specified.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to TI's AOQL (Average Outgoing Quality Level).
Output power is measured at the device terminals.
When driving 3Ω or 4Ω and operating on a 5V supply, the LM4863LQ and LM4863MTE must be mounted to the circuit board that has a
minimum of 2.5in2 of exposed, uninterrupted copper area connected to the WQFN package's exposed DAP.
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Electrical Characteristics for Bridged-Mode Operation (1)(2) (continued)
The following specifications apply for VDD= 5V unless otherwise specified. Limits apply for TA= 25°C.
Symbol
Parameter
Conditions
LM4863
Typical
(3)
Limit
(4)
Units
(Limits)
XTALK
Channel Separation
f = 1kHz, CB = 1.0μF
90
dB
SNR
Signal To Noise Ratio
VDD = 5V, PO = 1.1W, RL = 8Ω
98
dB
Electrical Characteristics for Single-Ended Operation
(1) (2)
The following specifications apply for VDD= 5V unless otherwise specified. Limits apply for TA= 25°C.
Symbol
Parameter
Conditions
LM4863
Typical
VOS
Output Offset Voltage
VIN = 0V
PO
Output Power
(3)
Limit
(4)
Units
(Limits)
5
50
mV (max)
THD+N = 0.5%, f = 1kHz, RL = 32Ω
85
75
mW (min)
THD+N = 1%, f = 1kHz, RL = 8Ω
340
mW
THD+N = 10%, f = 1kHz, RL = 8Ω
440
mW
THD+N
Total Harmonic Distortion+Noise
AV = −1, PO = 75mW, 20Hz ≤ f ≤ 20kHz,
RL = 32Ω
0.2
%
PSRR
Power Supply Rejection Ratio
CB = 1.0μF, VRIPPLE = 200mV RMS,
f = 1kHz
52
dB
XTALK
Channel Separation
f = 1kHz, CB = 1.0μF
60
dB
SNR
Signal To Noise Ratio
VDD = 5V, PO = 340mW, RL = 8Ω
95
dB
(1)
(2)
(3)
(4)
6
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 specify specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which ensure specific performance limits. This assumes that the device is within the
Operating Ratings. Specifications are not specified for parameters where no limit is given, however, the typical value is a good indication
of device performance.
The maximum power dissipation is dictated by TJMAX, θ JA, and the ambient temperature TA and must be derated at elevated
temperatures. The maximum allowable power dissipation is PDMAX = (TJMAX − T A)/θJA. For the LM4863, TJMAX = 150°C. For the θJAs for
different packages, please see Application Informationor the Absolute Maximum Ratings section.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to TI's AOQL (Average Outgoing Quality Level).
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Typical Performance Characteristics- PWP Specific Characteristics
LM4863MTE
THD+N
vs
Output Power
LM4863MTE
THD+N
vs
Frequency
Figure 5.
Figure 6.
LM4863MTE
THD+N
vs
Output Power
LM4863MTE
THD+N
vs
Frequency
Figure 7.
Figure 8.
LM4863MTE
Power Dissipation
vs
Power Output
LM4863MTE
Power Derating Curve
Figure 9.
Figure 10.
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Typical Performance Characteristics- PWP Specific Characteristics (continued)
LM4863MTE
Power Derating Curve
This curve shows the LM4863MTE's thermal dissipation ability at different ambient temperatures given these conditions: 500LFPM
+ JEDEC board: The part is soldered to a 1S2P 20-lead exposed-DAP TSSOP test board with 500 linear feet per minute of forced-air
flow across it. Board information - copper dimensions: 74x74mm, copper coverage: 100% (buried layer) and 12% (top/bottom
layers), 16 vias under the exposed-DAP. 500LFPM + 2.5in2: The part is soldered to a 2.5in2, 1 oz. copper plane with 500 linear feet
per minute of forced-air flow across it. 2.5in2: The part is soldered to a 2.5in2, 1oz. copper plane. Not Attached: The part is not
soldered down and is not forced-air cooled.
Figure 11.
8
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Non-PWP Specific Characteristics
THD+N
vs
Frequency
THD+N
vs
Frequency
Figure 12.
Figure 13.
THD+N
vs
Frequency
THD+N
vs
Output Power
Figure 14.
Figure 15.
THD+N
vs
Output Power
THD+N
vs
Output Power
Figure 16.
Figure 17.
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Non-PWP Specific Characteristics (continued)
10
THD+N
vs
Output Power
THD+N
vs
Frequency
Figure 18.
Figure 19.
THD+N
vs
Output Power
THD+N
vs
Frequency
Figure 20.
Figure 21.
Output Power vs
Load Resistance
Power Dissipation vs
Supply Voltage
Figure 22.
Figure 23.
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Non-PWP Specific Characteristics (continued)
Output Power vs
Supply Voltage
Output Power vs
Supply Voltage
Figure 24.
Figure 25.
Output Power vs
Supply Voltage
Output Power vs
Load Resistance
Figure 26.
Figure 27.
Output Power vs
Load Resistance
Power Dissipation vs
Output Power
Figure 28.
Figure 29.
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Non-PWP Specific Characteristics (continued)
12
Dropout Voltage vs
Supply Voltage
Power Derating Curve
Figure 30.
Figure 31.
Power Dissipation vs
Output Power
Noise Floor
Figure 32.
Figure 33.
Channel Separation
Channel Separation
Figure 34.
Figure 35.
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Non-PWP Specific Characteristics (continued)
Power Supply
Rejection Ratio
Open Loop
Frequency Response
Figure 36.
Figure 37.
Supply Current vs
Supply Voltage
Figure 38.
External Components Description
(Refer to Figure 39.)
Components
Functional Description
1.
Ri
The Inverting input resistance, along with Rf, set the closed-loop gain. Ri, along with Ci, form a high pass filter with fc =
1/(2πRiCi).
2.
Ci
The input coupling capacitor blocks DC voltage at the amplifier's input terminals. Ci, along with Ri, create a highpass filter
with fc = 1/(2πRiCi). Refer to SELECTING PROPER EXTERNAL COMPONENTS, for an explanation of determining the
value of Ci.
3.
Rf
The feedback resistance, along with Ri, set the closed-loop gain.
4.
Cs
The supply bypass capacitor. Refer to POWER SUPPLY BYPASSING for information about properly placing, and selecting
the value of, this capacitor.
5.
CB
The capacitor, CB, filters the half-supply voltage present on the BYPASS pin. Refer to SELECTING PROPER EXTERNAL
COMPONENTS section for information concerning proper placement and selecting CB's value.
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APPLICATION INFORMATION
EXPOSED-DAP PACKAGE PCB MOUNTING CONSIDERATIONS
The LM4863's exposed-DAP (die attach paddle) packages (PWP and NHW) 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 2.2W 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
LM4863's high power performance and activate unwanted, though necessary, thermal shutdown protection.
The PWP and NHW packages must have their DAPs 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 than two layers. Connect the DAP copper pad to the inner layer or
backside copper heat sink area with 32(4x8) (PWP) or 6(3x2) (NHW) vias. The via diameter should be 0.012in 0.013in with a 1.27mm pitch. Ensure efficient thermal conductivity by plating-through and solder-filling the vias.
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 LM4863 should be 5in2 (min) for the same supply
voltage and load resistance. The last two area recommendations apply for 25°c ambient temperature. Increase
the area to compensate for ambient temperatures above 25°c. In systems using cooling fans, the LM4863MTE
can take advantage of forced air cooling. With an air flow rate of 450 linear-feet per minute and a 2.5in2 exposed
copper or 5.0in2 inner layer copper plane heatsink, the LM4863MTE can continuously drive a 3Ω load to full
power. The LM4863LQ achieves the same output power level without forced air cooling. In all circumstances and
conditions, the junction temperature must be held below 150°C to prevent activating the LM4863's thermal
shutdown protection. The LM4863's power de-rating curve, Figure 31, in Non-PWP Specific Characteristics
shows the maximum power dissipation versus temperature. Example PCB layouts for the exposed-DAP TSSOP
and WQFN packages are shown in RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT. Further detailed
and specific information concerning PCB layout, fabrication, and mounting an WQFN package is available from
Texas Instruments' package Engineering Group. When contacting them, ask for "Preliminary Application Note for
the Assembly of the WQFN Package on a Printed Circuit Board, Revision A dated 7/14/00."
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 2.1W to 2.0W. 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.
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.
14
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* Refer to SELECTING PROPER EXTERNAL COMPONENTS, for a detailed discussion of CB size.
Pin out shown for the SOIC package. Refer to Connection Diagrams for the pinout of the TSSOP, Exposed-DAP
TSSOP, and Exposed-DAP WQFN packages.
Figure 39. Typical Audio Amplifier Application Circuit
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 39, the LM4863 consists of two pairs of operational amplifiers, forming a two-channel
(channel A and channel B) stereo amplifier. (Though the following discusses channel A, it applies equally to
channel B.) External resistors Rf and Ri set the closed-loop gain of Amp1A, whereas two internal 20kΩ resistors
set Amp2A's gain at -1. The LM4863 drives a load, such as a speaker, connected between the two amplifier
outputs, -OUTA and +OUTA.
Figure 39 shows that Amp1A's output serves as Amp2A's input. This results in both amplifiers producing signals
identical in magnitude, but 180° out of phase. Taking advantage of this phase difference, a load is placed
between -OUTA and +OUTA and driven differentially (commonly referred to as "bridge mode"). This results in a
differential gain of
AVD = 2 × (Rf / Ri)
(1)
Bridge mode amplifiers are different from single-ended amplifiers that drive loads connected between a single
amplifier's output and ground. For a given supply voltage, bridge mode has a distinct advantage over the singleended configuration: its differential output doubles the voltage swing across the load. This produces four times
the output power when 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 that the output signal is not clipped.
To ensure minimum output signal clipping when choosing an amplifier's closed-loop gain, refer to AUDIO
POWER AMPLIFIER DESIGN.
Another advantage of the differential bridge output is no net DC voltage across the load. This is accomplished by
biasing channel A's and channel B's outputs at half-supply. This eliminates the coupling capacitor that single
supply, single-ended amplifiers require. Eliminating an output coupling capacitor in a single-ended configuration
forces a single-supply amplifier's half-supply bias voltage across the load. This increases internal IC power
dissipation and may permanently damage loads such as speakers.
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POWER DISSIPATION
Power dissipation is a major concern when designing a successful single-ended or bridged amplifier. 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 / (2π2 RL) Single-Ended
(2)
However, a direct consequence of the increased power delivered to the load by a bridge amplifier is higher
internal power dissipation for the same conditions.
The LM4863 has two operational amplifiers per channel. The maximum internal power dissipation per channel
operating in the bridge mode is four times that of a single-ended amplifier. From Equation 3, assuming a 5V
power supply and an 4Ω load, the maximum single channel power dissipation is 1.27W or 2.54W for stereo
operation.
PDMAX = 4 × (VDD)2 / (2π2 RL) Bridge Mode
(3)
The LM4973's power dissipation is twice that given by Equation 2 or Equation 3 when operating in the singleended mode or bridge mode, respectively. Twice the maximum power dissipation point given by Equation 3 must
not exceed the power dissipation given by Equation 4:
PDMAX' = (TJMAX − TA) / θJA
(4)
The LM4863's TJMAX = 150°C. In the NHW (WQFN) package soldered to a DAP pad that expands to a copper
area of 5in2 on a PCB, the LM4863's θJA is 20°C/W. In the PWP package soldered to a DAP pad that expands to
a copper area of 2in2 on a PCB , the LM4863's θJA is 41°C/W. At any given ambient temperature TJ\A, use
Equation 4 to find the maximum internal power dissipation supported by the IC packaging. Rearranging
Equation 4 and substituting PDMAX for PDMAX' results in Equation 5. This equation gives the maximum ambient
temperature that still allows maximum stereo power dissipation without violating the LM4863's maximum junction
temperature.
TA = TJMAX − 2 × PDMAX θJA
(5)
For a typical application with a 5V power supply and an 4Ω load, the maximum ambient temperature that allows
maximum stereo power dissipation without exceeding the maximum junction temperature is approximately 99°C
for the WQFN package and 45°C for the PWP package.
TJMAX = PDMAX θJA + TA
(6)
Equation 6 gives the maximum junction temperature TJMAX. If the result violates the LM4863's 150°C, reduce the
maximum junction temperature by reducing the power supply voltage or increasing the load resistance. Further
allowance should be made for increased ambient temperatures.
The above examples assume that a device is a surface mount part operating around the maximum power
dissipation point. Since internal power dissipation is a function of output power, higher ambient temperatures are
allowed as output power or duty cycle decreases.
If the result of Equation 5 is greater than that of Equation 6, then decrease the supply voltage, increase the load
impedance, or reduce the ambient temperature. If these measures are insufficient, a heat sink can be added to
reduce θJA. The heat sink can be created using additional copper area around the package, with connections to
the ground pin(s), supply pin and amplifier output pins. External, solder attached SMT heatsinks such as the
Thermalloy 7106D can also improve power dissipation. When adding a heat sink, the θJA is the sum of θJC, θCS,
and θSA. (θJC is the junction−to−case thermal impedance, CS is the case−to−sink thermal impedance, and θSAis
the sink−to−ambient thermal impedance.) Refer to Typical Performance Characteristics for power dissipation
information at lower output power levels.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is critical for low noise performance and high power supply
rejection. Applications that employ a 5V regulator typically use a 10µF in parallel with a 0.1µF filter capacitors to
stabilize the regulator's output, reduce noise on the supply line, and improve the supply's transient response.
However, their presence does not eliminate the need for a local 1.0µF tantalum bypass capacitance connected
between the LM4863's supply pins and ground. Do not substitute a ceramic capacitor for the tantalum. Doing so
may cause oscillation in the output signal. Keep the length of leads and traces that connect capacitors between
the LM4863's power supply pin and ground as short as possible. Connecting a 1µF capacitor, CB, between the
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BYPASS pin and ground improves the internal bias voltage's stability and improves the amplifier's PSRR. The
PSRR improvements increase as the bypass pin capacitor value increases. Too large, however, increases turnon time and can compromise amplifier's click and pop performance. The selection of bypass capacitor values,
especially CB, depends on desired PSRR requirements, click and pop performance (as explained in SELECTING
PROPER EXTERNAL COMPONENTS, system cost, and size constraints.
MICRO-POWER SHUTDOWN
The voltage applied to the SHUTDOWN pin controls the LM4863's shutdown function. Activate micro-power
shutdown by applying VDD to the SHUTDOWN pin. When active, the LM4863's micro-power shutdown feature
turns off the amplifier's bias circuitry, reducing the supply current. The logic threshold is typically VDD/2. The low
0.7µA typical shutdown current is achieved by applying a voltage that is as near as VDD as possible to the
SHUTDOWN pin. A voltage thrat is less than VDD may increase the shutdown current.
There are a few ways to control the micro-power shutdown. These include using a single-pole, single-throw
switch, a microprocessor, or a microcontroller. When using a switch, connect an external 10kΩ pull-up resistor
between the SHUTDOWN pin and VDD. Connect the switch between the SHUTDOWN pin and ground. Select
normal amplifier operation by closing the switch. Opening the switch connects the SHUTDOWN pin to VDD
through the pull-up resistor, activating micro-power shutdown. The switch and resistor ensure that the
SHUTDOWN pin will not float. This prevents unwanted state changes. In a system with a microprocessor or a
microcontroller, use a digital output to apply the control voltage to the SHUTDOWN pin. Driving the SHUTDOWN
pin with active circuitry eliminates the pull up resistor.
Table 1. Logic level truth table for SHUTDOWN and HP-IN Operation
SHUTDOWN
HP-IN PIN
OPERATIONAL MODE
Low
logic Low
Bridged amplifiers
Low
logic High
Single-Ended amplifiers
High
logic Low
Micro-power Shutdown
High
logic High
Micro-power Shutdown
HP-IN FUNCTION
Applying a voltage between 4V and VDD to the LM4863's HP-IN headphone control pin turns off Amp2A and
Amp2B, muting a bridged-connected load. Quiescent current consumption is reduced when the IC is in this
single-ended mode.
Figure 40 shows the implementation of the LM4863's headphone control function. With no headphones
connected to the headphone jack, the R1-R2 voltage divider sets the voltage applied to the HP-IN pin (pin 16) at
approximately 50mV. This 50mV enables Amp1B and Amp2B, placing the LM4863's in bridged mode operation.
The output coupling capacitor blocks the amplifier's half-supply DC voltage, protecting the headphones.
While the LM4863 operates in bridged mode, the DC potential across the load is essentially 0V. The HP-IN
threshold is set at 4V. Therefore, even in an ideal situation, the output swing cannot cause a false single-ended
trigger. Connecting headphones to the headphone jack disconnects the headphone jack contact pin from -OUTA
and allows R1 to pull the HP Sense pin up to VDD. This enables the headphone function, turns off Amp2A and
Amp2B, and mutes the bridged speaker. The amplifier then drives the headphones, whose impedance is in
parallel with resistor R2 and R3. These resistors have negligible effect on the LM4863's output drive capability
since the typical impedance of headphones is 32Ω.
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Figure 40. Headphone Circuit
Figure 40 also shows the suggested headphone jack electrical connections. The jack is designed to mate with a
three-wire plug. The plug's tip and ring should each carry one of the two stereo output signals, whereas the
sleeve should carry the ground return. A headphone jack with one control pin contact is sufficient to drive the HPIN pin when connecting headphones.
A microprocessor or a switch can replace the headphone jack contact pin. When a microprocessor or switch
applies a voltage greater than 4V to the HP-IN pin, a bridge-connected speaker is muted and Amp1A and
Amp2A drive a pair of headphones.
SELECTING PROPER EXTERNAL COMPONENTS
Optimizing the LM4863's performance requires properly selecting external components. Though the LM4863
operates well when using external components with wide tolerances, best performance is achieved by optimizing
component values.
The LM4863 is unity-gain stable, giving a designer maximum design flexibility. The gain should be set to no more
than a given application requires. This allows the amplifier to achieve minimum THD+N and maximum signal-tonoise ratio. These parameters are compromised as the closed-loop gain increases. However, low gain demands
input signals with greater voltage swings to achieve maximum output power. Fortunately, many signal sources
such as audio CODECs have outputs of 1VRMS (2.83VP-P). Please refer to AUDIO POWER AMPLIFIER DESIGN
for more information on selecting the proper gain.
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires high value input coupling capacitor (Ci in Figure 39). A high
value capacitor can be expensive and may compromise space efficiency in portable designs. In many cases,
however, the speakers used in portable systems, whether internal or external, have little ability to reproduce
signals below 150Hz. Applications using speakers with this limited frequency response reap little improvement by
using large input capacitor.
Besides effecting system cost and size, Ci has an affect on the LM4863's click and pop performance. When the
supply voltage is first applied, a transient (pop) is created as the charge on the input capacitor changes from zero
to a quiescent state. The magnitude of the pop is directly proportional to the input capacitor's size. Higher value
capacitors need more time to reach a quiescent DC voltage (usually VDD/2) when charged with a fixed current.
The amplifier's output charges the input capacitor through the feedback resistor, Rf. Thus, pops can be
minimized by selecting an input capacitor value that is no higher than necessary to meet the desired -3dB
frequency.
A shown in Figure 39, the input resistor (RI) and the input capacitor, CI produce a −3dB high pass filter cutoff
frequency that is found using Equation 7.
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(7)
As an example when using a speaker with a low frequency limit of 150Hz, CI, using Equation 4, is 0.063µF. The
1.0µF CI shown in Figure 39 allows the LM4863 to drive high efficiency, full range speaker whose response
extends below 30Hz.
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful consideration should be paid to value of CB, the capacitor
connected to the BYPASS pin. Since CB determines how fast the LM4863 settles to quiescent operation, its
value is critical when minimizing turn−on pops. The slower the LM4863'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), produces a click-less and pop-less shutdown function. As discussed above,
choosing Ci no larger than necessary for the desired bandwidth helps minimize clicks and pops.
OPTIMIZING CLICK AND POP REDUCTION PERFORMANCE
The LM4863 contains circuitry to minimize turn-on and shutdown transients or "clicks and pop". For this
discussion, turn-on refers to either applying the power supply voltage or when the shutdown mode is deactivated.
While the power supply is ramping to its final value, the LM4863's internal amplifiers are configured as unity gain
buffers. An internal current source changes the voltage of the BYPASS pin in a controlled, linear manner. Ideally,
the input and outputs track the voltage applied to the BYPASS pin. The gain of the internal amplifiers remains
unity until the voltage on the bypass pin reaches 1/2 VDD. As soon as the voltage on the BYPASS pin is stable,
the device becomes fully operational. Although the bypass pin current cannot be modified, changing the size of
CB alters the device's turn-on time and the magnitude of "clicks and pops". Increasing the value of CB reduces
the magnitude of turn-on pops. However, this presents a tradeoff: as the size of CB increases, the turn-on time
increases. There is a linear relationship between the size of CB and the turn-on time. Here are some typical turnon times for various values of CB:
CB
TON
0.01µF
20 ms
0.1µF
200 ms
0.22µF
440 ms
0.47µF
940 ms
1.0µF
2 Sec
In order eliminate "clicks and pops", all capacitors must be discharged before turn-on. Rapidly switching VDD may
not allow the capacitors to fully discharge, which may cause "clicks and pops". In a single-ended configuration,
the output is coupled to the load by COUT. This capacitor usually has a high value. COUT discharges through
internal 20kΩ resistors. Depending on the size of COUT, the discharge time constant can be relatively large. To
reduce transients in single-ended mode, an external 1kΩ - 5kΩ resistor can be placed in parallel with the internal
20kΩ resistor. The tradeoff for using this resistor is increased quiescent current.
NO LOAD STABILITY
The LM4863 may exhibit low level oscillation when the load resistance is greater than 10kΩ. This oscillation only
occurs as the output signal swings near the supply voltages. Prevent this oscillation by connecting a 5kΩ
between the output pins and ground.
AUDIO POWER AMPLIFIER DESIGN
Audio Amplifier Design: Driving 1W into an 8Ω Load
The following are the desired operational parameters:
Power Output:
1Wrms
Load Impedance:
8Ω
Input Level:
1Vrms
Input Impedance:
20kΩ
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Bandwidth:
100Hz−20 kHz ± 0.25 dB
The design begins by specifying the minimum supply voltage necessary to obtain the specified output power.
One way to find the minimum supply voltage is to use Figure 24, Figure 25, and Figure 26 in Typical
Performance Characteristics. Another way, usingEquation 4, is to calculate the peak output voltage necessary to
achieve the desired output power for a given load impedance. To account for the amplifier's dropout voltage, two
additional voltages, based on Figure 30 in Typical Performance Characteristics, must be added to the result
obtained by Equation 8. The result in Equation 8.
(8)
(9)
VDD ≥ (VOUTPEAK + (VODTOP + VODBOT))
Figure 24 for an 8Ω load indicates a minimum supply voltage of 4.6V. This is easily met by the commonly used
5V supply voltage. The additional voltage creates the benefit of headroom, allowing the LM4863 to produce peak
output power in excess of 1W without clipping or other audible distortion. The choice of supply voltage must also
not create a situation that violates maximum power dissipation as explained above in POWER DISSIPATION.
After satisfying the LM4863's power dissipation requirements, the minimum differential gain is found using
Equation 10.
(10)
Thus, a minimum gain of 2.83 allows the LM4863's to reach full output swing and maintain low noise and THD+N
performance. For this example, let AVD = 3.
The amplifier's overall gain is set using the input (Ri) and feedback (Rf) resistors. With the desired input
impedance set at 20kΩ, the feedback resistor is found using Equation 11.
Rf/Ri = AVD/2
(11)
The value of Rf is 30kΩ.
The last step in this design example is setting the amplifier's −3dB frequency bandwidth. To achieve the desired
±0.25dB pass band magnitude variation limit, the low frequency response must extend to at least one−fifth the
lower bandwidth limit and the high frequency response must extend to at least five times the upper bandwidth
limit. The gain variation for both response limits is 0.17dB, well within the ±0.25dB desired limit. The results are
an
fL = 100Hz/5 = 20Hz
(12)
and an
FH = 20kHz×5 = 100kHz
(13)
As mentioned in SELECTING PROPER EXTERNAL COMPONENTS, Ri and Ci create a highpass filter that
sets the amplifier's lower bandpass frequency limit. Find the coupling capacitor's value usingEquation 14.
(14)
the result is
1/(2π*20kΩ*20Hz) = 0.398µF
(15)
Use a 0.39µF capacitor, the closest standard value.
The product of the desired high frequency cutoff (100kHz in this example) and the differential gain, AVD,
determines the upper passband response limit. With AVD = 3 and fH = 100kHz, the closed-loop gain bandwidth
product (GBWP) is 300kHz. This is less than the LM4863's 3.5MHz GBWP. With this margin, the amplifier can
be used in designs that require more differential gain while avoiding performance-restricting bandwidth
limitations.
RECOMMENDED PRINTED CIRCUIT BOARD LAYOUT
Figure 41 through Figure 44 show the recommended two-layer PC board layout that is optimized for the 20-pin
PWP-packaged LM4863 and associated external components. Figures 7 through 11 show the recommended
four-layer PC board layout that is optimized for the 24-pin NHW-packaged LM4863 and associated external
components. These circuits are designed for use with an external 5V supply and 4Ω speakers.
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These circuit boards are easy to use. Apply 5V and ground to the board's VDD and GND pads, respectively.
Connect 4Ω speakers between the board's -OUTA and +OUTA and OUTB and +OUTB pads.
Figure 41. PWP PC board layout:
all layers superimposed
Figure 44. Recommended PWP PC board layout:
bottom-side layout
Figure 42. PWP PC board layout:
Component-side Silkscreen
Figure 45. Recommended NHW PC board layout:
Component-side Silkscreen
Figure 43. Recommended PWP PC board layout:
Component-side layout
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Figure 46. Recommended NHW PC board layout:
Component-side layout
Figure 47. Recommended NHW PC board layout:
upper inner-layer layout
22
Figure 48. Recommended NHW PC board layout:
lower inner-layer layout
Figure 49. Recommended NHW PC board layout:
bottom-side layout
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REVISION HISTORY
Rev
Date
Description
1.1
10/30/06
Removed all references to the 16–lead plastic-PDIP
package.
F
5/2/2013
Changed layout of National Data Sheet to TI format
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM4863LQ/NOPB
ACTIVE
WQFN
NHW
24
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
L4863
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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