November 9, 2007
LM4947
Mono Class D and Stereo Audio Sub-System with OCL
Headphone Amplifier and National 3D
General Description
The LM4947 is an audio subsystem capable of efficiently de-
livering 500mW (Class D operation) of continuous average
power into a mono 8Ω bridged-tied load (BTL) with 1% THD
+N, 37mW (Class AB operation) power channel of continuous
average power into stereo 32Ω single-ended (SE) loads with
1% THD+N, or an output capacitor-less (OCL) configuration
with identical specification as the SE configuration, from a
3.3V power supply.
The LM4947 has six input channels: one pair for a two-chan-
nel stereo signal, the second pair for a secondary two-channel
stereo input, and the third pair for a differential single-channel
mono input. Additionally, the two sets of stereo inputs may be
configured as a single stereo differential input (differential left
and differential right). The LM4947 features a 32-step digital
volume control and eight distinct output modes. The digital
volume control, 3D enhancement, and output modes are pro-
grammed through a two-wire I2C compatible interface that
allows flexibility in routing and mixing audio channels.
The RF suppression circuitry in the LM4947 makes it well-
suited for GSM mobile phones and other portable applications
in which strong RF signals generated by an antenna (and long
output traces) may couple audibly into the amplifier.
The LM4947 is designed for cellular phones, PDAs, and other
portable handheld applications. It delivers high quality output
power from a surface-mount package and requires only eight
external components in the OCL mode (two additional com-
ponents in SE mode).
Key Specifications
■ THD+N at 1kHz, 500mW
into 8Ω BTL (3.3V) 1.0% (typ)
■ THD+N at 1kHz, 37mW
into 32Ω SE (3.3V) 1.0% (typ)
■ Single Supply Operation (VDD)2.7 to 5.5V
■ I2C Single Supply Operation 2.2 to 5.5V
Features
■I2C Control Interface
■I2C programmable National 3D Audio
■I2C controlled 32 step digital volume control (-59.5dB to
+18dB)
■Three independent volume channels (Left, Right, Mono)
■Eight distinct output modes
■Small, 25–bump micro SMD packaging
■“Click and Pop” suppression circuitry
■Thermal shutdown protection
■Low shutdown current (0.1μA, typ)
■RF suppression
■Differential mono and stereo inputs
■Stereo input mux
Applications
■Mobile Phones
■PDAs
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 201735 www.national.com
LM4947 Mono Class D and Stereo Audio Sub-System with OCL Headphone Amplifier
and National 3D
Typical Application
201735d3
FIGURE 1. Typical Audio Amplifier Application Circuit-Output Capacitor-less
201735d4
FIGURE 2. Typical Audio Amplifier Application Circuit-Single Ended
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LM4947
Connection Diagrams
25-Bump micro SMD
201735d2
Top View
micro SMD Marking
20173507
Top View
XY - Date Code
TT - Die Traceability
G - Boomer Family
XX - H1
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LM4947
Pin Descriptions
Bump Name Description
A1 RIN2 Right Input Channel 2 or Right Differential Input -
A2 LIN1 Left Input Channel 1 or Left Differential Input +
A3 MIN+ Mono Channel Non-inverting Input
A4 RHP3D1 Right Headphone 3D Input 1
A5 RHP3D2 Right Headphone 3D Input 2
B1 RIN1 Right Input Channel 1 or Right Differential Input +
B2 LIN2 Left Input Channel 2 or Left Differential Input -
B3 MIN- Mono Channel Inverting Input
B4 LHP3D1 Left Headphone 3D Input 2
B5 LHP3D2 Left Headphone 3D Input 1
C1 ADDR Address Identification
C2 SDA Serial Data Input
C3 SCL Serial Clock Input
C4 CBYPASS Half-Supply Bypass Capacitor
C5 VOC Headphone return bias output
D1 AVDD Analog Power Supply
D2 LSVDD Loudspeaker Power Supply
D3 I2CVDD I2C Interface Power Supply
D4 AVDD Analog Power Supply
D5 RHP Right Headphone Output
E1 LS- Loudspeaker Output Negative
E2 GND Ground
E3 LS+ Loudspeaker Output Positive
E4 GND Ground
E5 LHP Left Headphone Output
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LM4947
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 6.0V
Storage Temperature −65°C to +150°C
Input Voltage −0.3 to VDD +0.3
ESD Susceptibility (Note 3) 2.0kV
ESD Machine model (Note 6) 200V
Junction Temperature (TJ)150°C
Solder Information
Vapor Phase (60 sec.) 215°C
Infrared (15 sec.) 220°C
Thermal Resistance
θJA (typ) - TLA25CBA 65°C/W
Operating Ratings
Temperature Range −40°C to 85°C
Supply Voltage (VDD)2.7V ≤ VDD ≤ 5.5V
Supply Voltage (I2C) 2.2V ≤ VDD ≤ 5.5V
Supply Voltage (Loudspeaker VDD)2.7V ≤ VDD ≤ 5.5V
Electrical Characteristics 3.3V (Notes 2, 7)
The following specifications apply for VDD = 3.3V, TA = 25°C, and all gains are set for 0dB unless otherwise specified.
Symbol Parameter Conditions LM4947 Units
(Limits)
Typical
(Note 4)
Limits
(Note 5)
IDDQ Quiescent Supply Current
Output Modes 2, 4, 6
VIN = 0V; No load,
OCL = 0 (Table 2)
4.5 6.5 mA (max)
Output Modes 1, 3, 5, 7
VIN = 0V; No load, BTL,
OCL = 0 (Table 2)
6.5 8 mA (max)
ISD Shutdown Current Output Mode 0 0.1 1 µA (max)
VOS Output Offset Voltage VIN = 0V, Mode 7, Mono 2 15 mV (max)
VIN = 0V, Mode 7, Headphones 2 15 mV (max)
POOutput Power
MONO OUT; RL = 8Ω
THD+N = 1%; f = 1kHz, BTL, Mode 1 500 400 mW (min)
ROUT and LOUT; RL = 32Ω
THD+N = 1%; f = 1kHz, SE, Mode 4 37 33 mW (min)
THD+N Total Harmonic Distortion Plus
Noise
MONOOUT
f = 1kHz, POUT = 250mW;
RL = 8Ω, BTL, Mode 1
0.03 %
ROUT and LOUT
f = 1kHz, POUT = 12mW;
RL = 32Ω, SE, Mode 4
0.02 %
NOUT Output Noise
A-weighted, 0dB
inputs terminated, output referred
Speaker; Mode 1 39 μV
Speaker; Mode 3 39 μV
Speaker; Mode 5 42 μV
Speaker; Mode 7 38 μV
Headphone; SE, Mode 2 15 μV
Headphone; SE, Mode 4 15 μV
Headphone; SE, Mode 6 17 μV
Headphone; OCL, Mode 2 12 μV
Headphone; OCL, Mode 4 15 μV
Headphone; OCL, Mode 6 17 μV
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LM4947
Symbol Parameter Conditions LM4947 Units
(Limits)
Typical
(Note 4)
Limits
(Note 5)
PSRR
Power Supply Rejection Ratio
Loudspeaker out
VRIPPLE = 200mVPP; f = 217Hz,
RL = 8Ω, CB = 2.2µF, BTL
All audio inputs terminated to GND;
output referred
BTL, Output Mode 1 79 dB
BTL, Output Mode 3 78 dB
BTL, Output Mode 5 79 dB
BTL, Output Mode 7 80 dB
Power Supply Rejection Ratio
ROUT and LOUT
VRIPPLE = 200mVPP; f = 217Hz,
RL = 32Ω, CB = 2.2µF, BTL
All audio inputs terminated to GND;
output referred
SE, Output Mode 2 78 dB
SE, Output Mode 4 71 dB
SE, Output Mode 6 71 dB
OCL, Output Mode 2 83 dB
OCL, Output Mode 4 74 dB
OCL, Output Mode 6 74 dB
ηClass D Efficiency Output Mode 1, 3, 5 86 %
CMRR Common-Mode-Rejection Ratio f = 217Hz, VCM = 1Vpp,
Mode 1, BTL, RL = 8Ω –49 dB
XTALK Crosstalk
Headphone, PO = 12mW,
f = 1kHz, OCL, Mode 4, RL = 32Ω –58 dB
Headphone, PO = 12mW,
f = 1kHz, SE, Mode 4, RL = 32Ω –73 dB
TWU Wake-Up Time from Shutdown CB = 2.2µF, OCL, RL = 32Ω 90 ms
CB = 2.2µF, SE, RL = 32Ω 115 ms
Volume Control Step Size Error ±0.2 dB
Digital Volume Range
Input referred maximum attenuation -59.5 –60.25
–58.75
dB (min)
dB (max)
Input referred maximum gain +18 17.25
18.75
dB (min)
dB (max)
Mute Attenuation Output Mode 1, 3, 5 87 dB (min)
MONO_IN Input Impedance
RIN and LIN Input Impedance
Maximum gain setting 12 8
14
kΩ (min)
kΩ (max)
Maximum attenuation setting 100 75
125
kΩ (min)
kΩ (max)
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LM4947
Electrical Characteristics 5V (Notes 2, 7)
The following specifications apply for VDD = 5V, TA = 25°C and all gains are set for 0dB unless otherwise specified.
Symbol Parameter Conditions LM4947 Units
(Limits)
Typical
(Note 4)
Limits
(Note 5)
IDDQ Quiescent Supply Current
Output Modes 2, 4, 6
VIN = 0V; No load,
OCL = 0 (Table 2)
5.4 7.5 mA
Output Modes 1, 3, 5, 7
VIN = 0V; No load, BTL,
OCL = 0 (Table 2)
7.6 12 mA
ISD Shutdown Current Output Mode 0 0.1 1 µA (max)
VOS Output Offset Voltage VIN = 0V, Mode 7, Mono 2 15 mV (max)
VIN = 0V, Mode 7, Headphones 2 15 mV (max)
POOutput Power
MONOOUT; RL = 8Ω
THD+N = 1%; f = 1kHz, BTL, Mode 1 1.19 W
ROUT and LOUT; RL = 32Ω
THD+N = 1%; f = 1kHz, SE, Mode 4 87 mW
THD+N Total Harmonic Distortion + Noise
MONOOUT
f = 1kHz, POUT = 500mW;
RL = 8Ω, BTL, Mode 1
0.04 %
ROUT and LOUT
f = 1kHz, POUT = 30mW;
RL = 32Ω, SE, Mode 4
0.01 %
NOUT Output Noise
A-weighted, 0dB
inputs terminated, output referred
Speaker; Mode 1 38 μV
Speaker; Mode 3 38 μV
Speaker; Mode 5 39 μV
Speaker; Mode 7 36 μV
Headphone; SE, Mode 2 21 μV
Headphone; SE, Mode 4 21 μV
Headphone; SE, Mode 6 24 μV
Headphone; OCL, Mode 2 16 μV
Headphone; OCL, Mode 4 16 μV
Headphone; OCL, Mode 6 19 μV
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LM4947
Symbol Parameter Conditions LM4947 Units
(Limits)
Typical
(Note 4)
Limits
(Note 5)
PSRR
Power Supply Rejection Ratio
Loudspeaker out
VRIPPLE = 200mVPP; f = 217Hz,
RL = 8Ω, CB = 2.2µF, BTL
All audio inputs terminated to GND;
output referred
BTL, Output Mode 1 70 dB
BTL, Output Mode 3 61 dB
BTL, Output Mode 5 64 dB
BTL, Output Mode 7 61 dB
Power Supply Rejection Ratio
ROUT and LOUT
VRIPPLE = 200mVPP; f = 217Hz,
RL = 32Ω, CB = 2.2µF, BTL
All audio inputs terminated to GND;
output referred
SE, Output Mode 2 72 dB
SE, Output Mode 4 70 dB
SE, Output Mode 6 65 dB
OCL, Output Mode 2 76 dB
OCL, Output Mode 4 72 dB
OCL, Output Mode 6 70 dB
ηClass D Efficiency Output Mode 1, 3, 5 86 %
CMRR Common-Mode Rejection Ratio f = 1kHz, VCM = 1Vpp, 0dB gain,
Mode 1, BTL, RL = 8Ω –49 dB
XTALK Crosstalk
Headphone, PO = 30mW, f = 1kHz,
OCL, Mode 4 –55 dB
Headphone, PO = 30mW, f = 1kHz,
SE, Mode 4 –72 dB
TWU Wake-Up Time from Shutdown CB = 2.2μF, OCL, RL = 32Ω 116 ms
CB = 2.2μF, SE, RL = 32Ω 150 ms
Volume Control Step Size Error ±0.2 dB
Digital Volume Range Input referred maximum attenuation -59.5 dB
Input referred maximum gain +18 dB
Mute Attenuation Output Mode 1, 3, 5 90 dB (min)
MONO_IN Input Impedance
RIN and LIN Input Impedance
Maximum gain setting 11 kΩ (min)
kΩ (max)
Maximum attenuation setting 100 kΩ (min)
kΩ (max)
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LM4947
I2C (Notes 2, 7)
The following specifications apply for VDD = 5V and 3.3V, TA = 25°C unless otherwise specified.
Symbol Parameter Conditions LM4947 Units
(Limits)
Typical
(Note 4)
Limits
(Note 5)
t1Clock Period 2.5 µs (max)
t2Clock Setup Time 100 ns (min)
t3Data Hold Time 100 ns (min)
t4Start Condition Time 100 ns (min)
t5Stop Condition Time 100 ns (min)
VIH SPI Input Voltage High 0.7xI2C
VDD
V (min)
VIL SPI Input Voltage Low 0.3xI2C
VDD
V (max)
I2C Protocol Information
The I2C address for the LM4947 is determined using the
ID_ENB pin. The LM4947's two possible I2C chip addresses
are of the form 111110X10 (binary), where X1 = 0, if ID_ADDR
is logic LOW; and X1 = 1, if ID_ENB is logic HIGH. If the I2C
interface is used to address a number of chips in a system,
the LM4947's chip address can be changed to avoid any pos-
sible address conflicts.
201735f5
FIGURE 3. I2C Bus Format
201735f4
FIGURE 4. I2C Timing Diagram
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LM4947
Note 1: See AN-450 "Surface Mounting and their effects on Product Reliability" for other methods of soldering surface mount devices.
Note 2: Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. For guaranteed specifications
and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance characteristics
may degrade when the device is not operated under the listed test conditions.
Note 3: Human body model, 100pF discharged through a 1.5kΩ resistor.
Note 4: Typical specifications are specified at +25°C and represent the most likely parametric norm.
Note 5: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 6: Machine Model ESD test is covered by specification EIAJ IC-121-1981. A 200pF cap is charged to the specified voltage, then discharged directly into
the IC with no external series resistor (resistance of discharge path must be under 50Ω).
Note 7: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 8: The given θJA for an LM4947TL mounted on a demonstration board with a 9in2 area of 1oz printed circuit board copper ground plane.
Note 9: Datasheet min/max specifications are guaranteed by design, test, or statistical analysis.
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LM4947
Typical Performance Characteristics
THD+N vs Output Power
VDD = 3.3V, RL = 8Ω, f = 1kHz
Mode 1, MONO
20173543
THD+N vs Output Power
VDD = 3.3V, RL = 8Ω, f = 1kHz
Mode 3, MONO
20173544
THD+N vs Output Power
VDD = 3.3V, RL = 8Ω, f = 1kHz
Mode 5, MONO
20173545
THD+N vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz, Diff In
Mode 2, OCL
20173546
THD+N vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz, Diff In
Mode 2, SE
20173547
THD+N vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz, Diff In
Mode 4, OCL
20173548
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LM4947
THD+N vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz, Diff In
Mode 4, SE
20173549
THD+N vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz, Diff In
Mode 6, OCL
20173550
THD+N vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz, Diff In
Mode 6, SE
20173515
THD+N vs Output Power
VDD = 5V, RL = 8Ω, f = 1kHz
Mode 1, MONO
20173552
THD+N vs Output Power
VDD = 5V, RL = 8Ω, f = 1kHz
Mode 3, MONO
20173553
THD+N vs Output Power
VDD = 5V, RL = 8Ω, f = 1kHz
Mode 5, MONO
20173554
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LM4947
THD+N vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz, Diff In
Mode 2, OCL
20173555
THD+N vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz, Diff In
Mode 2, SE
20173556
THD+N vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz, Diff In
Mode 4, OCL
20173557
THD+N vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz, Diff In
Mode 4, SE
20173558
THD+N vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz, Diff In
Mode 6, OCL
20173559
THD+N vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz, Diff In
Mode 6, SE
20173560
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LM4947
THD+N vs Frequency
VDD = 3.3V, RL = 8Ω, PO = 250mW
Diff In, Mode 1
20173525
THD+N vs Frequency
VDD = 3.3V, RL = 8Ω, PO = 250mW
Diff In, Mode 5
20173526
THD+N vs Frequency
VDD = 3.3V, RL = 8Ω, PO = 250mW
Diff In, Mode 3
20173527
THD+N vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 2, OCL
20173528
THD+N vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 2, SE
20173529
THD+N vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 4,7, OCL
20173530
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LM4947
THD+N vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 4,7, SE
20173531
THD+N vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 6, OCL
20173532
THD+N vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 6, SE
20173533
THD+N vs Frequency
VDD = 5V, RL = 8Ω, PO = 500mW
Diff In, Mode 1
20173534
THD+N vs Frequency
VDD = 5V, RL = 8Ω, PO = 500mW
Diff In, Mode 3
20173535
THD+N vs Frequency
VDD = 5V, RL = 8Ω, PO = 500mW
Diff In, Mode 5
20173536
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LM4947
THD+N vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Diff In, Mode 2, OCL
20173537
THD+N vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Diff In, Mode 2, SE
20173538
THD+N vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Diff In, Mode 4,7, OCL
20173539
THD+N vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Diff In, Mode 4,7, SE
20173540
THD+N vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Diff In, Mode 6, OCL
20173541
THD+N vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Diff In, Mode 6, SE
20173542
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LM4947
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 1, MONO
20173516
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 2, OCL
20173517
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 2, SE
20173518
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 3, MONO
20173519
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 4, OCL
20173520
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 4, SE
20173521
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LM4947
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 5, MONO
20173522
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 6, OCL
20173523
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 6, SE
201735a4
PSRR vs Frequency
VDD = 3.3V, AV = 0dB
Mode 7, MONO
201735a5
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 1, MONO
201735a6
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 2, OCL
201735a7
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LM4947
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 2, SE
201735a8
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 3, MONO
201735a9
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 4, OCL
201735b0
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 4, SE
201735b1
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 5, MONO
201735b2
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 6, OCL
201735b3
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LM4947
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 6, SE
201735b4
PSRR vs Frequency
VDD = 5V, AV = 0dB
Mode 7, MONO
201735b5
Power Dissipation vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz
Mode 7, OCL
201735c9
Power Dissipation vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz
Mode 7, SE
201735d0
Power Dissipation vs Output Power
VDD = 3.3V, RL = 8Ω, f = 1kHz
Mode 1, 3, 5, MONO
201735c8
Power Dissipation vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz
Mode 2, 4, 6, OCL
201735b6
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LM4947
Power Dissipation vs Output Power
VDD = 3.3V, RL = 32Ω, f = 1kHz
Mode 2, 4, 6, SE
20173598
Power Dissipation vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz
Mode 7, OCL
201735c0
Power Dissipation vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz
Mode 7, SE
201735c1
Power Dissipation vs Output Power
VDD = 5V, RL = 8Ω, f = 1kHz
Mode 1, 3, 5, MONO
201735b7
Power Dissipation vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz
Mode 2, 4, 6, OCL
201735b8
Power Dissipation vs Output Power
VDD = 5V, RL = 32Ω, f = 1kHz
Mode 2, 4, 6, SE
201735b9
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LM4947
Crosstalk vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 4, OCL
20173573
Crosstalk vs Frequency
VDD = 3.3V, RL = 32Ω, PO = 12mW
Mode 4, SE
20173574
Crosstalk vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Mode 4, OCL
20173575
Crosstalk vs Frequency
VDD = 5V, RL = 32Ω, PO = 30mW
Mode 4, SE
20173576
Supply Current vs Supply Voltage
No Load, Mode 7, OCL
201735c2
Supply Current vs Supply Voltage
No Load, Mode 7, SE
20173578
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LM4947
Supply Current vs Supply Voltage
No Load, Mode 1, 3, 5, MONO
201735d1
Supply Current vs Supply Voltage
No Load, Mode 2, 4, 6, OCL
201735c4
Supply Current vs Supply Voltage
No Load, Mode 2, 4, 6, Headphone SE
20173581
Output Power vs Supply Voltage
RL = 8Ω, Mode 1, 3, 5, MONO
20173587
Output Power vs Supply Voltage
RL = 32Ω, Mode 2, 4, 6, OCL
201735c7
Output Power vs Supply Voltage
RL = 32Ω, Mode 2, 4, 6, SE
20173589
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LM4947
Output Power vs Supply Voltage
RL = 32Ω, Mode 7, OCL
20173590
Output Power vs Supply Voltage
RL = 32Ω, Mode 7, SE
20173591
Efficiency vs Output Power
VDD = 3.3V, RL = 8Ω, Mode 1, 3, 5, BTL
20173513
Efficiency vs Output Power
VDD = 5V, RL = 8Ω, Mode 1, 3, 5, BTL
201735c6
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LM4947
Application Information
I2C PIN DESCRIPTION
SDA: This is the serial data input pin.
SCL: This is the clock input pin.
ID_ENB: This is the address select input pin.
I2C COMPATIBLE INTERFACE
The LM4947 uses a serial bus which conforms to the I2C pro-
tocol to control the chip's functions with two wires: clock (SCL)
and data (SDA). The clock line is uni-directional. The data line
is bi-directional (open-collector). The maximum clock fre-
quency specified by the I2C standard is 400kHz. In this dis-
cussion, the master is the controlling microcontroller and the
slave is the LM4947.
The I2C address for the LM4947 is determined using the
ID_ENB pin. The LM4947's two possible I2C chip addresses
are of the form 111110X10 (binary), where X1 = 0, if ID_ADDR
is logic LOW; and X1 = 1, if ID_ENB is logic HIGH. If the I2C
interface is used to address a number of chips in a system,
the LM4947's chip address can be changed to avoid any pos-
sible address conflicts.
The bus format for the I2C interface is shown in Figure 3. The
bus format diagram is broken up into six major sections:
The "start" signal is generated by lowering the data signal
while the clock signal is HIGH. The start signal will alert all
devices attached to the I2C bus to check the incoming address
against their own address.
The 8-bit chip address is sent next, most significant bit first.
The data is latched in on the rising edge of the clock. Each
address bit must be stable while the clock level is HIGH.
After the last bit of the address bit is sent, the master releases
the data line HIGH (through a pull-up resistor). Then the mas-
ter sends an acknowledge clock pulse. If the LM4947 has
received the address correctly, then it holds the data line LOW
during the clock pulse. If the data line is not held LOW during
the acknowledge clock pulse, then the master should abort
the rest of the data transfer to the LM4947.
The 8 bits of data are sent next, most significant bit first. Each
data bit should be valid while the clock level is stable HIGH.
After the data byte is sent, the master must check for another
acknowledge to see if the LM4947 received the data.
The "stop" signal ends the transfer. To signal "stop", the data
signal goes HIGH while the clock signal is HIGH. The data
line should be held HIGH when not in use.
I2C INTERFACE POWER SUPPLY PIN (I2CVDD)
The LM4947's I2C interface is powered up through the
I2CVDD pin. The LM4947's I2C interface operates at a voltage
level set by the I2CVDD pin which can be set independent to
that of the main power supply pin VDD. This is ideal whenever
logic levels for the I2C interface are dictated by a microcon-
troller or microprocessor that is operating at a lower supply
voltage than the main battery of a portable system.
TABLE 1. Chip Address
A7 A6 A5 A4 A3 A2 A1 A0
Chip
Address 111110EC0
ID_ADDR =
0
11111000
ID_ADDR =
1
11111010
TABLE 2. Control Registers
D7 D6 D5 D4 D3 D2 D1 D0
Mode Control 0 0 SE/Diff
(select)
0 OCL (select) MC2 MC1 MC0
Programmable 3D 0 1 L2R2
(select)
L1R1 (select) N3D3 N3D2 N3D1 N3D0
Mono Volume Control 1 0 0 MVC4 MVC3 MVC2 MVC1 MVC0
Left Volume Control 1 1 0 LVC4 LVC3 LVC2 LVC1 LVC0
Right Volume Control 1 1 1 RVC4 RVC3 RVC2 RVC1 RVC0
1. Bits MVC0 — MVC4 control 32 step volume control for MONO input
2. Bits LVC0 — LVC4 control 32 step volume control for LEFT input
3. Bits RVC0 — RVC4 control 32 step volume control for RIGHT input
4. Bits MC0 — MC2 control 8 distinct modes
5. Bits N3D3, N3D2, N3D1, N3D0 control programmable 3D function
6. N3D0 turns the 3D function ON (N3D0 = 1) or OFF (N3D0 = 0)
7. Bit OCL selects between SE with output capacitor (OCL = 0) or SE without output capacitors (OCL = 1). Default is OCL = 0
8. N3D1 selects between two different 3D configurations
9. SE/Diff-SE/Diff = 0 for SE mode; SE/Diff = 1 for Diff mode
25 www.national.com
LM4947
TABLE 3. Programmable National 3D Audio
N3D3 N3D2
Low 0 0
Medium 0 1
High 1 0
Maximum 1 1
TABLE 4. Input/Output Control
L2R2 L1R1 SE/DIFF
Select LIN1 and RIN1 Stereo Pair 0 1 0
Select LIN2 and RIN2 Stereo Pair 1 0 0
Select LIN1+LIN2 and RIN1+RIN2 Stereo Pair 1 1 0
Sets Stereo Inputs to Differential x x 1
X = Don't Care
www.national.com 26
LM4947
TABLE 5. Output Volume Control Table
Volume Step xVC4 xVC3 xVC2 xVC1 xVC0 Gain, dB
1 0 0 0 0 0 –59.50
2 0 0 0 0 1 –48.00
3 0 0 0 1 0 –40.50
4 0 0 0 1 1 –34.50
5 0 0 1 0 0 –30.00
6 0 0 1 0 1 –27.00
7 0 0 1 1 0 –24.00
8 0 0 1 1 1 –21.00
9 0 1 0 0 0 –18.00
10 0 1 0 0 1 –15.00
11 0 1 0 1 0 –13.50
12 0 1 0 1 1 –12.00
13 0 1 1 0 0 –10.50
14 0 1 1 0 1 –9.00
15 0 1 1 1 0 –7.50
16 0 1 1 1 1 –6.00
17 1 0 0 0 0 –4.50
18 1 0 0 0 1 –3.00
19 1 0 0 1 0 –1.50
20 1 0 0 1 1 0.00
21 1 0 1 0 0 1.50
22 1 0 1 0 1 3.00
23 1 0 1 1 0 4.50
24 1 0 1 1 1 6.00
25 1 1 0 0 0 7.50
26 1 1 0 0 1 9.00
27 1 1 0 1 0 10.50
28 1 1 0 1 1 12.00
29 1 1 1 0 0 13.50
30 1 1 1 0 1 15.00
31 1 1 1 1 0 16.50
32 1 1 1 1 1 18.00
1. x = M, L, or R
27 www.national.com
LM4947
TABLE 6. Output Mode Selection
Output
Mode
Number
MC2 MC1 MC0 Handsfree Mono Output Right HP Output Left HP Output
0 0 0 0 SD SD SD
1 0 0 1 2 x GM x M MUTE MUTE
2 0 1 0 SD GM x M GM x M
3 0 1 1 GL x L + GR x R MUTE MUTE
4 1 0 0 SD GR x R GL x L
5 1 0 1 GL x L + GR x R + 2(GM x M) MUTE MUTE
6 1 1 0 SD GR x R + GM x M GL x L + GM x M
7 1 1 1 GR x R + GL x L GR x R GL x L
Note: L and R are selected by modes from Table 4.
On initial POWER ON, the default mode is 000
M = Mono
R = RIN
L = LIN
SD = Shutdown
MUTE = Mute Mode
GM = Mono volume control gain
GR = Right stereo volume control gain
GL = Left stereo volume control gain
NATIONAL 3D ENHANCEMENT
The LM4947 features a stereo headphone, 3D audio en-
hancement effect that widens the perceived soundstage from
a stereo audio signal. The 3D audio enhancement creates a
perceived spatial effect optimized for stereo headphone lis-
tening. The LM4947 can be programmed for a “narrow” or
“wide” soundstage perception. The narrow soundstage has a
more focused approaching sound direction, while the wide
soundstage has a spatial, theater-like effect. Within each of
these two modes, four discrete levels of 3D effect that can be
programmed: low, medium, high, and maximum (Table 2),
each level with an ever increasing aural effect, respectively.
The difference between each level is 3dB.
The external capacitors, shown in Figure 6, are required to
enable the 3D effect. The value of the capacitors set the cutoff
frequency of the 3D effect, as shown by Equations 1 and 2.
Note that the internal 20kΩ resistor is nominal (±25%).
20173509
FIGURE 5. External 3D Effect Capacitors
f3DL(-3dB) = 1 / 2π * 20kΩ * C3DL (1)
f3DR(-3dB) = 1 / 2π * 20kΩ * C3DR (2)
Optional resistors R3DL and R3DR can also be added (Figure
7) to affect the -3dB frequency and 3D magnitude.
20173508
FIGURE 6. External RC Network with Optional R3DL and
R3DR Resistors
f3DL(-3dB) = 1 / 2π * (20kΩ + R3DL) * C3DL (3)
f3DR(-3dB) = 1 / 2π * 20kΩ + R3DR) * C3DR (4)
www.national.com 28
LM4947
ΔAV (change in AC gain) = 1 / 1 + M, where M represents
some ratio of the nominal internal resistor, 20kΩ (see exam-
ple below).
f3dB (3D) = 1 / 2π (1 + M)(20kΩ * C3D) (5)
CEquivalent (new) = C3D / 1 + M (6)
TABLE 7. Pole Locations
R3D (kΩ)
(optional)
C3D (nF) M ΔAV (dB) f-3dB (3D)
(Hz)
Value of C3D
to keep same
pole location
(nF)
new Pole
Location
(Hz)
0 68 0 0 117
1 68 0.05 –0.4 111 64.8 117
5 68 0.25 –1.9 94 54.4 117
10 68 0.50 –3.5 78 45.3 117
20 68 1.00 –6.0 59 34.0 117
PCB LAYOUT AND SUPPLY REGULATION
CONSIDERATIONS FOR DRIVING 8Ω LOAD
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 ex-
ample, 0.1Ω trace resistance reduces the output power dis-
sipated by an 8Ω load from 158.3mW to 156.4mW. The
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 de-
creases with increasing load current. Reduced supply voltage
causes decreased headroom, output signal clipping, and re-
duced output power. Even with tightly regulated supplies,
trace resistance creates the same effects as poor supply reg-
ulation. Therefore, making the power supply traces as wide
as possible helps maintain full output voltage swing.
POWER DISSIPATION AND EFFICIENCY
In general terms, efficiency is considered to be the ratio of
useful work output divided by the total energy required to pro-
duce it with the difference being the power dissipated, typi-
cally, in the IC. The key here is “useful” work. For audio
systems, the energy delivered in the audible bands is con-
sidered useful including the distortion products of the input
signal. Sub-sonic (DC) and super-sonic components
(>22kHz) are not useful. The difference between the power
flowing from the power supply and the audio band power be-
ing transduced is dissipated in the LM4947 and in the trans-
ducer load. The amount of power dissipation in the LM4947
is very low. This is because the ON resistance of the switches
used to form the output waveforms is typically less than
0.25Ω. This leaves only the transducer load as a potential
"sink" for the small excess of input power over audio band
output power. The LM4947 dissipates only a fraction of the
excess power requiring no additional PCB area or copper
plane to act as a heat sink.
The LM4947 also has a pair of single-ended amplifiers driving
stereo headphones, RHP and LHP. The maximum internal
power dissipation for RHP and LHP is given by equation (9) and
(10). From Equations (9) and (10), assuming a 5V power sup-
ply and a 32Ω load, the maximum power dissipation for LHP
and RHP is 40mW, or 80mW total.
PDMAX-LHP = (VDD)2 / (2π2 RL): Single-ended Mode (7)
PDMAX-RHP = (VDD)2 / (2π2 RL): Single-ended Mode (8)
The maximum internal power dissipation of the LM4947 oc-
curs when all 3 amplifiers pairs are simultaneously on; and is
given by Equation (11).
PDMAX-TOTAL =
PDMAX-SPKROUT + PDMAX-LHP + PDMAX-RHP (9)
The maximum power dissipation point given by Equation (11)
must not exceed the power dissipation given by Equation
(12):
PDMAX = (TJMAX - TA) / θJA (10)
The LM4947's TJMAX = 150°C. In the ITL package, the
LM4947's θJA is 65°C/W. At any given ambient temperature
TA, use Equation (12) to find the maximum internal power
dissipation supported by the IC packaging. Rearranging
Equation (12) and substituting PDMAX-TOTAL for PDMAX' results
in Equation (13). This equation gives the maximum ambient
temperature that still allows maximum stereo power dissipa-
tion without violating the LM4947's maximum junction tem-
perature.
TA = TJMAX - PDMAX-TOTAL θJA (11)
For a typical application with a 5V power supply and an 8Ω
load, the maximum ambient temperature that allows maxi-
mum stereo power dissipation without exceeding the maxi-
mum junction temperature is approximately 104°C for the ITL
package.
TJMAX = PDMAX-TOTAL θJA + TA(12)
Equation (14) gives the maximum junction temperature
TJMAX. If the result violates the LM4947's 150°C, reduce the
maximum junction temperature by reducing the power supply
29 www.national.com
LM4947
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 (11) is greater
than that of Equation (12), then decrease the supply voltage,
increase the load impedance, or reduce the ambient temper-
ature. If these measures are insufficient, a heat sink can be
added to reduce θJA. The heat sink can be created using ad-
ditional copper area around the package, with connections to
the ground pin(s), supply pin and amplifier output pins. Ex-
ternal, 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, θCS is the case-to-sink
thermal impedance, and θSA is the sink-to-ambient thermal
impedance). Refer to the Typical Performance Characteris-
tics curves for power dissipation information at lower output
power levels.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is crit-
ical for low noise performance and high power supply rejec-
tion. Applications that employ a 5V regulator typically use a
1µF in parallel with a 0.1µF filter capacitors to stabilize the
regulator's output, reduce noise on the supply line, and im-
prove the supply's transient response. However, their pres-
ence does not eliminate the need for a local 1.1µF tantalum
bypass capacitance connected between the LM4947's supply
pins and ground. Keep the length of leads and traces that
connect capacitors between the LM4947's power supply pin
and ground as short as possible. Connecting a 2.2µF capac-
itor, CB, between the 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
turn-on time and can compromise the amplifier's click and pop
performance. The selection of bypass capacitor values, es-
pecially CB, depends on desired PSRR requirements, click
and pop performance (as explained in the section, Proper
Selection of External Components), system cost, and size
constraints.
SELECTING EXTERNAL COMPONENTS
Input Capacitor Value Selection
Amplifying the lowest audio frequencies requires high value
input coupling capacitor (Ci in Figures 1 & 2). A high value
capacitor can be expensive and may compromise space ef-
ficiency in portable designs. In many cases, however, the
speakers used in portable systems, whether internal or ex-
ternal, have little ability to reproduce signals below 150Hz.
Applications using speakers with this limited frequency re-
sponse reap little improvement by using large input capacitor.
The internal input resistor (Ri), nominal 20kΩ, and the input
capacitor (Ci) produce a high pass filter cutoff frequency that
is found using Equation (15).
fc = 1 / (2πRiCi) (13)
As an example when using a speaker with a low frequency
limit of 150Hz, Ci, using Equation (15) is 0.053µF. The 0.22µF
Ci shown in Figure 1 allows the LM4947 to drive high effi-
ciency, full range speaker whose response extends below
40Hz.
Bypass Capacitor Value Selection
Besides minimizing the input capacitor size, careful consid-
eration should be paid to value of CB, the capacitor connected
to the BYPASS bump. Since CB determines how fast the
LM4947 settles to quiescent operation, its value is critical
when minimizing turn-on pops. The slower the LM4947's out-
puts ramp to their quiescent DC voltage (nominally VDD/2),
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), pro-
duces a click-less and pop-less shutdown function. As dis-
cussed above, choosing Ci no larger than necessary for the
desired bandwidth helps minimize clicks and pops. CB's value
should be in the range of 5 times to 7 times the value of Ci.
This ensures that output transients are eliminated when pow-
er is first applied or the LM4947 resumes operation after
shutdown.
www.national.com 30
LM4947
DEMO BOARD SCHEMATIC
20173510
31 www.national.com
LM4947
Revision History
Rev Date Description
1.0 06/16/06 Initial release.
1.1 06/19/06 Changed the Class D Efficiency (n) on Typical limit (from 79 to 86) on the
5V specification table.
1.2 06/22/06 Added more Typ Perf curves.
1.3 07/18/06 Replaced some of the curves.
1.4 08/29/06 Text edits.
1.5 10/18/06 Edited micro SMD pkg drawing, Figure 1, and Figure 2.
Changed IDDQ typical and limit values on the 3.3V and 5.0V specification
table.
Removed CMRR SE condition and changed typical values for CMRR BTL
on 3.3V and 5.0V specification table.
Changed Mute Attenuation typical value on 5.0V specification table.
1.6 03/02/07 Edited the 3.3V and 5V EC tables.
1.7 03/02/07 Composed (CONFIDENTIAL) D/S for customer (SAMSUNG).
1.8 09/06/07 Edited Table 4.
1.9 11/09/07 Text edits.
www.national.com 32
LM4947
Physical Dimensions inches (millimeters) unless otherwise noted
25 – Bump micro SMD
Order Number LM4947TL
NS Package Number TLA25BBA
Dimensions are in millimeters
X1 = 2.517 ± 0.01 X2 = 2.517 ± 0.01 X3 = 0.600 ± 0.10
33 www.national.com
LM4947
Notes
LM4947 Mono Class D and Stereo Audio Sub-System with OCL Headphone Amplifier
and National 3D
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