LM4949
LM4949 Stereo Class D Audio Subsystem with OCL Headphone Amplifier
Literature Number: SNAS368C
January 2007
LM4949
Stereo Class D Audio Subsystem with OCL Headphone
Amplifier
General Description
The LM4949 is a fully integrated audio subsystem designed
for stereo cell phone applications. The LM4949 combines a
2.5W stereo Class D amplifier plus a separate 190mW stereo
headphone amplifier, volume control, and input mixer into a
single device. The filterless class D amplifiers deliver 1.19W/
channel into an 8Ω load with <1% THD+N from a 5V supply.
The headphone amplifier features National’s Output Capaci-
tor-less (OCL) architecture that eliminates the output coupling
capacitors required by traditional headphone amplifiers. Ad-
ditionally, the headphone amplifiers can be configured with
capacitively coupled (CC)loads, or used to drive an external
headphone amplifier. When configured for an external ampli-
fier, the VDD/2 output (VOC) controls the external amplifier’s
shutdown input.
For improved noise immunity, the LM4949 features fully dif-
ferential left, right and mono inputs. The three inputs can be
mixed/multiplexed to either the speaker or headphone ampli-
fiers. The left and right inputs can be used as separate single-
ended inputs, mixing multiple stereo audio sources. The
mixer, volume control, and device mode select are controlled
through an I2C compatible interface.
Output short circuit and thermal shutdown protection prevent
the device from being damaged during fault conditions. Su-
perior click and pop suppression eliminates audible transients
on power-up/down and during shutdown.
Key Specifications
■ Efficiency VDD = 3.6V, 400mW
into 8Ω86.5%
■ Efficiency VDD = 5V, 1W into 8Ω87.4%
■ Quiescent Power Supply Current
@ 3.6V 9.36mA
■ Power Output at VDD = 5V
Speaker:
RL = 4Ω, THD+N ≤ 1%
RL = 8Ω, THD+N ≤ 1%
RL = 4Ω, THD+N ≤ 10%
2W
1.19W
2.5W
Headphone:
RL = 16Ω, THD+N ≤ 1%
RL = 32Ω, THD+N ≤ 1%
153mW
89mW
■ Shutdown Current 0.1μA
Features
■Output Short Circuit Protection
■Thermal Shutdown
■Stereo filterless Class D operation
■Selectable OCL/CC Headphone Drivers
■RF Suppression
■I2C Control Interface
■32-step digital volume control
■Independent Speaker and Headphone Gain Settings
■Minimum external components
■Click and Pop suppression
■Micro-power shutdown
■Available in space-saving 25 bump µSMD package
Applications
■Mobile phones
■PDAs
■Laptops
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2007 National Semiconductor Corporation 202001 www.national.com
LM4949 Stereo Class D Audio Subsystem with OCL Headphone Amplifier
Typical Application
202001c6
FIGURE 1. Typical Audio Amplifier Application Circuit
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LM4949
Connection Diagrams
TL Package
2.68mm x 2.68mm x 0.6mm
202001c7
Top View
Order Number LM4949TL
See NS Package Number TLA25JJA
LM4949TL Marking
202001c0
Top View
XY — 2 digit datecode
TT — Die traceability
3 www.national.com
LM4949
Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (Note 1) 6.0V
Storage Temperature −65°C to +150°C
Input Voltage −0.3V to VDD +0.3V
Power Dissipation (Note 3) Internally Limited
ESD Susceptibility (Note 4) 2000V
ESD Susceptibility (Note 5) 200V
Junction Temperature 150°C
Thermal Resistance
θJA 35.1°C/W
Operating Ratings
Temperature Range
TMIN ≤ TA ≤ TMAX −40°C ≤ TA ≤ +85°C
Supply Voltage (VDD, VDDLS,
VDDHP)
2.7V ≤ VDD≤ 5.5V
I2C Voltage (I2CVDD)2.4V ≤ I2CVDD≤ 5.5V
Electrical Characteristics VDD = 3.0V (Notes 1, 2) The following specifications apply for AV = 0dB, RL
(SP) = 15μH + 8Ω + 15μH, RL(HP) = 32Ω, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C.
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
IDD Supply Current
LS Mode
Stereo
Mono
6
4.5
8.75 mA (max)
mA
OCL HP Mode
Stereo
Mono
5.0
4.3
6.5 mA (max)
mA
CC HP Mode
Stereo
Mono
4.0
3.3
5.25 mA (max)
mA
Stereo LS + HP Mode 8.6 mA
ISD Shutdown Supply Current 0.03 2 µA (max)
VOS Output Offset Voltage Speaker (mode 1)
OCL HP (mode 1)
8.9
5.6
48.9
24.5
mV (max)
mV (max)
POUT Output Power
LS Mode, f = 1 kHz
RL = 4Ω, THD+N = 10%
RL = 4Ω, THD+N = 1%
RL = 8Ω, THD+N = 10%
RL = 8Ω, THD+N = 1%
820
662
515
415 340
mW
mW
mW
mW (min)
OCP HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
62.5
50
37.5
30.3
mW
mW
mW
mW
CC HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
63
50
38
30
mW
mW
mW
mW (min)
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LM4949
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
THD+N Total Harmonic Distortion + Noise
Differential Mode, f = 1kHz
HP Mode, RL = 16Ω, POUT = 35mW
OCL
CC
0.015
0.012
%
%
HP Mode, RL = 32Ω, POUT = 20mW
OCL
CC
0.017
0.018
%
%
LS Mode
RL = 4Ω, POUT = 300mW
RL = 8Ω, POUT = 150mW
0.023
0.02
%
%
THD+N Total Harmonic Distortion + Noise
Single-Ended Input Mode, f = 1kHz
HP Mode, RL = 16Ω, POUT = 35mW
OCL
CC
0.023
0.017
%
%
HP Mode, RL = 32Ω, POUT = 20mW
OCL
CC
0.019
0.013
%
%
LS Mode
RL = 4Ω, POUT = 300mW
RL = 8Ω, POUT = 150mW
0.05
0.03
%
%
eNNoise
Differential Input, A-weighted, Input Referred
Mono Input
OCL
CC
LS
16.4
15.5
43
μV
μV
μV
All Inputs ON
OCL
CC
LS
29.8
29.2
46.6
μV
μV
μV
Single-Ended Input, A-weighted, Input Referred
Stereo Input
OCL
CC
LA
12
11
45
μV
μV
μV
All Inputs ON
OCL
CC
LS
23.7
22.9
52
μV
μV
μV
ηEfficiency LS Mode, POUT = 400mW, RL = 8Ω 85.3 %
Xtalk Crosstalk
LS Mode, f = 1kHz, RL = 8Ω, VIN = 1VP-P
Differential Input Mode 84.7 dB
OCL HP Mode, f = 1kHz, RL = 32Ω, VIN = 1VP-P
Differential Input Mode 68 dB
TON Turn on Time
CC Mode
OCL Mode
LS Mode
68
14
29
ms
ms
ms
TOFF Turn off Time From any mode 683 ms
ZIN Input Impedance Maximum Gain
Minimum Gain
24.8
222.7
kΩ
kΩ
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LM4949
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
AVGain
Volume Control
Minimum Gain
Maximum Gain
–57
18
dB
dB
LS Second Gain Stage
Step 0
Differential Input
Single-Ended Input
6
12
dB
dB
Step 1
Differential Input
Single-Ended Input
4
10
dB
dB
Step 2
Differential Input
Single-Ended Input
2
8
dB
dB
Step 3
Differential Input
Single-Ended Input
0
6
dB
dB
HP Second Gain Stage
Step 0
Step 1
Step 2
0
-6
-12
dB
dB
dB
Mute Mute Attenuation Speaker Mode –103 dB
Headphone Mode –123 dB
CMRR Common Mode Rejection Ratio
Speaker Mode, f = 1kHz,
VIN = 200mVP-P
66.1 dB
OCL Headphone Mode, f = 1kHz,
VIN = 200mVP-P
70 dB
PSRR Power Supply Rejection Ratio
Differential Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 1kHz
78.1
75.4
74
72.9
dB
dB
dB
dB
PSRR Power Supply Rejection Ratio
Single-Ended Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 70.31kHz72.8
77.5
81
69
81
dB
dB
dB
dB
PSRR Power Supply Rejection Ratio
All Inputs ON, Single-Ended Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 1kHz
66.1
70.5
65.4
72.2
dB
dB
dB
dB
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LM4949
Electrical Characteristics VDD = 3.6V (Notes 1, 2) The following specifications apply for AV = 0dB, RL
(SP) = 15μH + 8Ω + 15μH, RL(HP) = 32Ω, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C.
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
IDD Supply Current
LS Mode
Stereo
Mono
6.8
4.9
7.3
5.3
mA (max)
mA (max)
OCL HP Mode
Stereo
Mono
5.8
4.9
6.5
5.5
mA (max)
mA (max)
CC HP Mode
Stereo
Mono
4.7
4.1
5.2
4.6
mA (max)
mA (max)
Stereo LS + HP Mode 9.36 mA
ISD Shutdown Supply Current 0.03 1 µA (max)
VOS Output Offset Voltage Headphone
Speaker
6.7
8.9
20
49
mV (max)
mV (max)
POUT Output Power
LS Mode, f = 1 kHz
RL = 4Ω, THD+N = 10%
RL = 4Ω, THD+N = 1%
RL = 8Ω, THD+N = 10%
RL = 8Ω, THD+N = 1%
1.24
1
0.765
0.615
W
W
W
W
OCL HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
94
76
55
45
mW
mW
mW
mW
CC HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
93
75
56
45
mW
mW
mW
mW
THD+N Total Harmonic Distortion + Noise
Differential Mode, f = 1kHz
HP Mode, RL = 16Ω, POUT = 50mW
OCL
CC
0.021
0.021
%
%
HP Mode, RL = 32Ω,
POUT = 30mW
OCL
CC
0.01
0.01
%
%
LS Mode
RL = 4Ω, POUT = 400mW
RL = 8Ω, POUT = 300mW
0.023
0.02
%
%
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LM4949
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
THD+N Total Harmonic Distortion + Noise
Single-Ended Input Mode, f = 1kHz
HP Mode, RL = 16Ω, POUT = 50mW
OCL
CC
0.021
0.017
%
%
HP Mode, RL = 32Ω, POUT = 30mW
OCL
CC
0.02
0.015
%
%
LS Mode
RL = 4Ω, POUT = 400mW
RL = 8Ω, POUT = 300mW
0.05
0.034
%
%
eNNoise
Differential Mode, A-weighted, Input Referred
Mono Input
OCL
CC
LS
16.4
15.5
43
μV
μV
μV
All Inputs ON
OCL
CC
LS
29.8
29.2
46.6
μV
μV
μV
Single-Ended Input, A-weighted, Input Referred
Stereo Input
OCL
CC
LS
12
11
45
μV
μV
μV
All Inputs ON
OCL
CC
LS
23.7
22.9
52
μV
μV
μV
ηEfficiency LS Mode, POUT = 400mW, RL = 8Ω 86.5 %
Xtalk Crosstalk
LS Mode, f = 1kHz, RL = 8Ω, VIN = 1VP-P
Differential Input Mode 86 dB
OCL HP Mode, f = 1kHz, RL = 32Ω, VIN = 1VP-P
Differential Input Mode 68 dB
TON Turn on Time
CC Mode
OCL Mode
LS Mode
75
14
31
ms
ms
TOFF Turn off Time From any mode 692 ms
ZIN Input Impedance Maximum Gain
Minimum Gain
24.8
222.7
kΩ
kΩ
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LM4949
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
AVGain
Volume Control
Minimum Gain
Maximum Gain
–57
18
dB
dB
LS Second Gain Stage
Step 0
Differential Input
Single-Ended Input
6
12
dB
dB
Step 2
Differential Input
Single-Ended Input
4
10
dB
dB
Step 2
Differential Input
Single-Ended Input
2
8
dB
dB
Step 3
Differential Input
Single-Ended Input
0
6
dB
dB
HP Second Gain Stage
Step 0
Step 1
Step 2
0
–6
–12
dB
dB
Mute Mute Attenuation Speaker Mode –84 dB
Headphone Mode –95 dB
CMRR Common Mode Rejection Ratio
Speaker Mode, f = 1kHz,
VIN = 200mVP-P
66 dB
OCL Headphone Mode, f = 1kHz,
VIN = 200mVP-P
68.6 dB
PSRR Power Supply Rejection Ratio
Differential Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 1kHz
75
75
73
73
dB
dB
dB
dB
PSRR Power Supply Rejection Ratio
Single-Ended Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 1kHz
75
75
67
71
dB
dB
dB
dB
PSRR Power Supply Rejection Ratio
All Inputs ON, Single-Ended Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 1kHz
72
70
60
65
dB
dB
dB
dB
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LM4949
Electrical Characteristics VDD = 5.0V (Notes 1, 2) The following specifications apply for AV = 0dB, RL
(SP) = 15μH + 8Ω + 15μH, RL(HP) = 32Ω, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C.
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
IDD Supply Current
LS Mode
Stereo
Mono
9.9
6.6
10.9
7.2
mA (max)
mA (max)
OCL HP Mode
Stereo
Mono
6.6
5.5
7.3
6.2
mA (max)
mA (max)
CC HP Mode
Stereo
Mono
5.4
4.3
5.9
4.8
mA (max)
mA (max)
Stereo LS + HP Mode 13 mA
ISD Shutdown Supply Current 0.1 1 µA (max)
VOS Output Offset Voltage Headphone
Speaker
10
9.6
52
50
mV (max)
mV (max)
POUT Output Power
LS Mode, f = 1 kHz
RL = 4Ω, THD+N = 10%
RL = 4Ω, THD+N = 1%
RL = 8Ω, THD+N = 10%
RL = 8Ω, THD+N = 1%
2.5
2.01
1.48
1.19
W
W
W
W
OCL HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
190
154
109
89
mW
mW
mW
mW
CC HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
188
153
105
88
mW
mW
mW
mW
THD + N Total Harmonic Distortion + Noise
Differential Input Mode, f = 1kHz
HP Mode, RL = 16Ω, POUT = 100mW
OCL
CC
0.02
0.027
%
%
HP Mode, RL = 32Ω, POUT = 50mW
OCL
CC
0.02
0.022
%
%
LS Mode
RL = 4Ω, POUT = 1W
RL = 8Ω, POUT = 600mW
0.022
0.02
%
%
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LM4949
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
THD + N Total Harmonic Distortion + Noise
Single-Ended Input Mode, f = 1kHz
HP Mode, RL = 16Ω, POUT = 100mW
OCL
CC
0.021
0.02
%
%
HP Mode, RL = 32Ω, POUT = 50mW
OCL
CC
0.02
0.017
%
%
LS Mode
RL = 4Ω, POUT = 1W
RL = 8Ω, POUT = 600mW
0.05
0.033
%
%
eNNoise
Differential Input, A-weighted, Input Referred
Mono Input
OCL
CC
LS
16.4
15.5
43
μV
μV
μV
All Inputs ON
OCL
CC
LS
29.8
29.2
46.6
μV
μV
μV
Single-Ended Input, A-weighted, Input Rrferred
Stereo Input
OCL
CC
LS
12
11
45
μV
μV
μV
All Inputs ON
OCL
CC
LS
23.7
22.9
52
μV
μV
μV
ηEfficiency LS Mode, POUT = 1W, RL = 8Ω 87.4 %
Xtalk Crosstalk
LS Mode, f = 1kHz, RL = 8Ω, VIN = 1VP-P
Differential Input Mode 105.8 dB
OCL HP Mode, f = 1kHz, RL = 32Ω, VIN = 1VP-P
Differential Input Mode 69.6 dB
TON
Turn on Time
CC Mode
OCL Mode
LS Mode
89
14
35
ms
ms
ms
TOFF Turn off Time From any mode 716 ms
ZIN Input Impedance Maximum Gain
Minimum Gain
24.8
222.7
kΩ
kΩ
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LM4949
Symbol Parameter Conditions
LM4949 Units
(Limits)
Typical Limit
(Note 6) (Notes 7, 8)
AVGain
Volume Control
Minimum Gain
Maximum Gain
–57
18
dB
dB
LS Second Gain Stage
Step 0
Differential Input
Single-Ended Input
6
12
dB
dB
Step 1
Differential Input
Single-Ended Input
4
10
dB
dB
Step 2
Differential Input
Single-Ended Input
8
2
dB
dB
Step 3
Differential Input
Single-Ended Input
0
6
dB
dB
HP Second Gain Stage
Step 0
Step 1
Step 2
0
–6
–12
dB
dB
dB
Mute Mute Attenuation Speaker Mode –102.7 dB
Headphone Mode –123 dB
CMRR Common Mode Rejection Ratio
Speaker Mode, f = 1kHz,
VIN = 200mVP-P
64.4 dB
OCL Headphone Mode, f = 1kHz,
VIN = 200mVP-P
74.3 dB
PSRR Power Supply Rejection Ratio
Differential Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz 68.3 dB
OCL HP Mode, f = 1kHz 67.9 dB
LS Mode, f = 217Hz 73.8 dB
LS Mode, f = 1kHz 72 dB
PSRR Power Supply Rejection Ratio
Single-Ended Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz 70.55 dB
OCL HP Mode, f = 1kHz 63.05 dB
LS Mode, f = 217Hz 64.6 dB
LS Mode, f = 1kHz 70.3 dB
PSRR Power Supply Rejection Ratio
All Inputs ON, Single-Ended Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz 63.1 dB
OCL HP Mode, f = 1kHz 66.4 dB
LS Mode, f = 217Hz 59.1 dB
LS Mode, f = 1kHz 69.3 dB
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LM4949
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 LM4949, 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: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 8: Datasheet min/max specification limits are guaranteed by design, test or statistical analysis.
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LM4949
TABLE 1. Bump Description
BUMP NAME DESCRIPTION
A1 LLS- Left Channel Loudspeaker Inverting Output
A2 LLS+ Left Channel Loudspeaker Non-inverting Output
A3 SDA Serial Data Input
A4 HPGND Headphone Ground
A5 HPR Right Channel Headphone Output
B1 VDDLS Speaker Power Supply
B2 ADR Address Select Bit
B3 RIN- Right Channel Inverting Input
B4 HPL Left Channel Headphone Output
B5 VOC Headphone Return Bias Output
C1 GNDLS Speaker Ground
C2 VDD Power Supply
C3 RIN+ Right Channel Non-Inverting Input
C4 LIN+ Left Channel Non-inverting Input
C5 VDDHP Headphone Power Supply
D1 VDDLS Speaker Power Supply
D2 I2CVDD I2C Power Supply
D3 SCL Serial Clock Input
D4 MIN+ Mono Channel Non-inverting Input
D5 LIN- Left Channel Inverting Input
E1 RLS- Right Channel Loudspeaker Inverting Output
E2 RLS+ Right Channel Loudspeaker Non-inverting Output
E3 GND Ground
E4 MIN- Mono Channel Inverting Input
E5 BYPASS Mid-rail Bias Bypass
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LM4949
Typical Performance Characteristics
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.0V, POUT = 300mW, RL = 4Ω
202001f0
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, POUT = 400mW, RL = 4Ω
202001f1
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 5.0V, POUT = 1W, RL = 4Ω
202001f2
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.0V, POUT = 150mW, RL = 8Ω
202001f3
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, POUT = 300mW, RL = 8Ω
202001f4
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 5.0V, POUT = 600mW, RL = 8Ω
202001f5
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LM4949
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.0V, POUT = 300mW, RL = 4Ω
202001f6
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.6V, POUT = 400mW, RL = 4Ω
202001f7
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 5.0V, POUT = 1W, RL = 4Ω
202001f8
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.0V, POUT = 150mW, RL = 8Ω
202001f9
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.6V, POUT = 300mW, RL = 8Ω
202001g0
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 5.0V, POUT = 600mW, RL = 8Ω
202001g1
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LM4949
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
202001g2
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001g3
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
202001g4
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001g5
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
202001g6
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001g7
17 www.national.com
LM4949
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
202001g8
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001g9
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
202001h0
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001h1
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
202001h2
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001h3
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LM4949
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
202001h4
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001h5
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
202001h6
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001h7
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
202001h8
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001h9
19 www.national.com
LM4949
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
202001i3
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001i4
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
202001i5
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001i6
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
202001i7
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001i8
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LM4949
THD+N vs Output Power
Speaker Mode, Differential Input
AV = 6dB, RL = 4Ω, f = 1kHz
202001d0
THD+N vs Output Power
Speaker Mode, Differential Input
AV = 6dB, RL = 8Ω, f = 1kHz
202001d1
THD+N vs Output Power
Speaker Mode, Single-Ended Input
AV = 6dB, RL = 4Ω, f = 1kHz
202001d2
THD+N vs Output Power
Speaker Mode, Single-Ended Input
AV = 6dB, RL = 8Ω, f = 1kHz
202001d3
THD+N vs Output Power
OCL Headphone Mode, Differential Input
AV = 0dB, RL = 16Ω, f = 1kHz
202001d4
THD+N vs Output Power
OCL Headphone Mode, Differential Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001d5
21 www.national.com
LM4949
THD+N vs Output Power
OCL Headphone Mode, Single-Ended Input
AV = 0dB, RL = 16Ω, f = 1kHz
202001d6
THD+N vs Output Power
OCL Headphone Mode, Single-Ended Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001d7
THD+N vs Output Power
CC Headphone Mode, Differential Input
AV = 0dB, RL = 16Ω, f = 1kHz
202001d8
THD+N vs Output Power
CC Headphone Mode, Differential Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001d9
THD+N vs Output Power
CC Headphone Mode, Single-Ended Input
AV = 0dB, RL = 16Ω, f = 1kHz
202001e0
THD+N vs Output Power
CC Headphone Mode, Single-Ended Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001e1
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LM4949
PSRR vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 8Ω
202001i9
PSRR vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 8Ω
202001j0
PSRR vs Frequency
Speaker Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 8Ω
202001j1
PSRR vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j2
PSRR vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j3
PSRR vs Frequency
OCL Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j4
23 www.national.com
LM4949
PSRR vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j5
PSRR vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j6
PSRR vs Frequency
CC Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j7
Efficiency vs Output Power
Speaker Mode
RL = 32Ω, f = 1kHz
202001e2
Efficiency vs Output Power
Speaker Mode
RL = 8Ω, f = 1kHz
202001e3
Power Dissipation vs Output Power
Speaker Mode
RL = 4Ω, f = 1kHz
20200139
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LM4949
Power Dissipation vs Output Power
Speaker Mode
RL = 8Ω, f = 1kHz
20200140
Power Dissipation vs Output Power
OCL Headphone Mode
RL = 16Ω, f = 1kHz
20200168
Power Dissipation vs Output Power
OCL Headphone Mode
RL = 32Ω, f = 1kHz
20200169
Power Dissipation vs Output Power
CC Headphone Mode
RL = 16Ω, f = 1kHz
20200195
Power Dissipation vs Output Power
CC Headphone Mode
RL = 32Ω, f = 1kHz
20200196
Output Power vs Supply Voltage
Speaker Mode
RL = 4Ω, f = 1kHz
202001e4
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LM4949
Output Power vs Supply Voltage
Speaker Mode
RL = 8Ω, f = 1kHz
202001e5
Output Power vs Supply Voltage
OCL Headphone Mode
RL = 16Ω, f = 1kHz
202001e6
Output Power vs Supply Voltage
OCL Headphone Mode
RL = 32Ω, f = 1kHz
202001e7
Output Power vs Supply Voltage
CC Headphone Mode
RL = 16Ω, f = 1kHz
202001e8
Output Power vs Supply Voltage
CC Headphone Mode
RL = 32Ω, f = 1kHz
202001e9
CMRR vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, VCM = 1VP-P, RL = 8Ω, f = 1kHz
202001j8
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LM4949
CMRR vs Frequency
OCL Headphone Mode
VDD = 3.6V, VCM = 1VP-P, RL = 32Ω
202001j9
CMRR vs Frequency
CC Headphone Mode
VDD = 3.6V, VCM = 1VP-P, RL = 32Ω
202001k3
Output Noise vs Frequency
Speaker Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, RL = 8Ω
202001k0
Output Noise vs Frequency
OCL Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, RL = 32Ω
202001k1
Output Noise vs Frequency
CC Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, RL = 32Ω
202001k2
Crosstalk vs Frequency
Speaker Mode
VDD = 3.6V, VRIPPLE = 1VP-P, RL = 8Ω
202001i0
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LM4949
Crosstalk vs Frequency
OCL Headphone Mode
VDD = 3.6V, VRIPPLE = 1VP-P, RL = 32Ω
202001i1
Crosstalk vs Frequency
CC Headphone Mode
VDD = 3.6V, VRIPPLE = 1VP-P, RL = 32Ω
202001i2
Supply Current vs Supply Voltage
Speaker Mode, No Load
202001b1
Supply Current vs Supply Voltage
OCL Headphone Mode, No Load
202001b4
Supply Current vs Supply Voltage
CC Headphone Mode, No Load
202001b7
Supply Current vs Supply Voltage
Speaker and OCL Headphone Mode, No Load
202001b8
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LM4949
Supply Current vs Supply Voltage
Shutdown Mode, No Load
202001b9
Turn-On
OCL Headphone Mode
20200113
Turn-Off
OCL Headphone Mode
20200114
Turn-On
CC Headphone Mode
20200115
Turn-Off
CC Headphone Mode
20200116
29 www.national.com
LM4949
Application Information
I2C COMPATIBLE INTERFACE
The LM4949 is controlled through an I2C compatible serial
interface that consists of two wires; clock (SCL) and data
(SDA). The clock line is uni-directional. The data line is bi-
directional (open-collector) although the LM4949 does not
write to the I2C bus. The maximum clock frequency specified
by the I2C standard is 400kHz.
To avoid an address conflict with another device on the I2C
bus, the LM4949 address is determined by the ADR pin, the
state of ADR determines address bit A1 (Table 2). When ADR
= 0, the address is 1111 1000. When ADR = 1 the device
address is 1111 1010.
TABLE 2. Device Address
ADR A7 A6 A5 A4 A3 A2 A1 A0
X 111110X0
0 11111000
1 11111010
BUS FORMAT
The I2C bus format is shown in Figure 2. The “start” signal is
generated by lowering the data signal while the clock is high.
The start signal alerts all devices on the bus that a device
address is being written to the bus.
The 8-bit device address is written to the bus next, most sig-
nificant bit first. The data is latched in on the rising edge of the
clock. Each address bit must be stable while the clock is high.
After the last address bit is sent, the master device releases
the data line, during which time, an acknowledge clock pulse
is generated. If the LM4949 receives the address correctly,
then the LM4949 pulls the data line low, generating an ac-
knowledge bit (ACK).
Once the master device has registered the ACK bit, the 8-bit
register address/data word is sent. Each data bit should be
stable while the clock level is high. After the 8–bit word is sent,
the LM4949 sends another ACK bit. Following the acknowl-
edgement of the data word, the master device issues a “stop”
bit, allowing SDA to go high while the clock signal is high.
20200109
FIGURE 2. I2C Bus Format
20200110
FIGURE 3. I2C Timing Diagram
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LM4949
TABLE 3. I2C Control Registers
REGISTE
R
REGISTE
R NAME
D7 D6 D5 D4 D3 D2 D1 D0
0.0 Shutdown
Control 0 0 0 0 0 OCL_LGC *OCL *PWR_ON
0.1
Stereo
Input Mode
Control
0 0 0 1 L1_INSEL L2_INSEL SDB_HPSEL SDB_MUXSE
L
1
Speaker
Output
Mux
Control
0 0 1 LS_XSEL LSR_MSEL LSR_SSEL LSL_MSEL LSL_SSEL
2
Headphon
e Output
Mux
Control
0 1 0 HP_XSEL HPR_MSEL HPR_SSEL HPL_MSEL HPL_SSEL
3.0 Output On/
Off Control 0 1 1 0 HPR_ON HPL_ON LSR_ON LSL_ON
3.1 Reserved 0 1 1 1 RESERVED RESERVED RESERVED RESERVED
4.0
Headphon
e Output
Stage Gain
Control
1 0 0 0 HPG1 HPG0 RESERVED RESERVED
4.1
Speaker
Output
Stage Gain
Control
1 0 0 1 LSRG1 LSRG0 LSLG1 LSLG0
5
Mono Input
Gain
Control
1 0 1 MG4 MG3 MG2 MG1 MG0
6
Left Input
Gain
Control
1 1 0 LG4 LG3 LG2 LG1 LG0
7
Right Input
Gain
Control
1 1 1 RG4 RG3 RG2 RG1 RG0
* Note: OCL_LGC = 1 and OCL = 1 at the same time is not allowed.
31 www.national.com
LM4949
GENERAL AMPLIFIER FUNCTION
Class D Amplifier
The LM4949 features a high-efficiency, filterless, Class D
stereo amplifier. The LM4949 Class D amplifiers feature a fil-
terless modulation scheme, the differential outputs of each
channel switch at 300khz, from VDD to GND. When there is
no input signal applied, the two outputs (_LS+ and _LS-)
switch with a 50% duty cycle, with both outputs in phase. Be-
cause the outputs of the LM4949 are differential, the two
signals cancel each other. This results in no net voltage
across the speaker, thus no load current during the idle state,
conserving power.
When an input signal is applied, the duty cycle (pulse width)
changes. For increasing output voltages, the duty cycle of
_LS+ increases, while the duty cycle of _LS- decreases. For
decreasing output voltages, the converse occurs, the duty
cycle of _LS- increases while the duty cycle of _LS+ decreas-
es. The difference between the two pulse widths yields the
differential output voltage.
Headphone Amplifier
The LM4949 headphone amplifier features three different op-
erating modes, output capacitorless (OCL), capacitor-cou-
pled (CC), and external amplifier mode.
The OCL architecture eliminates the bulky, expensive output
coupling capacitors required by traditional headphone ampli-
fiers. The LM4949 headphone section uses three amplifiers.
Two amplifiers drive the headphones while the third (VOC) is
set to the internally generated bias voltage (typically VDD/2).
The third amplifier is connected to the return terminal of the
headphone jack. In this configuration, the signal side of the
headphones are biased to VDD/2, the return is biased to
VDD/2, thus there is no net DC voltage across the headphone,
eliminating the need for an output coupling capacitor. Re-
moving the output coupling capacitors from the headphone
signal path reduces component count, reducing system cost
and board space consumption, as well as improving low fre-
quency performance.
In OCL mode, the headphone return sleeve is biased to
VDD/2. When driving headphones, the voltage on the return
sleeve is not an issue. However, if the headphone output is
used as a line out, the VDD/2 can conflict with the GND po-
tential that a line-in would expect on the return sleeve. When
the return of the headphone jack is connected to GND, the
VOC amplifier of the LM4949 detects an output short circuit
condition and is disabled, preventing damage to the LM4949,
and allowing the headphone return to be biased at GND.
Capacitor Coupled Headphone Mode
In capacitor coupled (CC) mode, the VOC pin is disabled, and
the headphone outputs are coupled to the jack through series
capacitors, allowing the headphone return to be connected to
GND (Figure 4). In CC mode, the LM4949 requires output
coupling capacitors to block the DC component of the ampli-
fier output, preventing DC current from flowing to the load.
The output capacitor and speaker impedance form a high
pass filter with a -3dB roll-off determined by:
f-3dB = 1 / 2πRLCOUT
Where RL is the headphone impedance, and COUT is the out-
put coupling capacitor. Choose COUT such that f-3dB is well
below the lowest frequency of interest. Setting f-3dB too high
results in poor low frequency performance. Select capacitor
dielectric types with low ESR to minimize signal loss due to
capacitor series resistance and maximize power transfer to
the load.
20200105
FIGURE 4. Capacitor Coupled Headphone Mode
External Headphone Amplifier
The LM4949 features the ability to drive and control a sepa-
rate headphone amplifier for applications that require a True
Ground headphone output (Figure 5). Configure the LM4949
into external headphone amplifier mode by setting bit D2
(OCL_LGC) in register 0.0 to 1 and bit D1 (OCL) to 0. In this
mode the VOC output becomes a logic output used to drive
the shutdown input of the external amplifier. The output level
of VOC is controlled by bits D1 (SDB_HPSEL) and D2
(SDB_MUXSEL) in register 0.1. SDB_MUXSEL determines
the source of the VOC control signal. With SDB_MUXSEL =
0, the VOC signal comes from the internal start-up circuitry of
the LM4949. This allows the external headphone amplifier to
be turned on and off simultaneously with the LM4949. When
SDB_MUXSEL = 1, the VOC signal comes from the I2C bus,
bit D1. With SDB_HPSEL = 0, VOC is a logic low, with
SDB_HPSEL = 1, VOC is a logic high.
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LM4949
202001c8
FIGURE 5. Driving an External Headphone Amplifier
33 www.national.com
LM4949
Single-Ended Input
The left and right stereo inputs of the LM4949 can be config-
ured for single-ended sources (Figure 6). In single-ended
input mode, the LM4949 can accept up to 4 different single-
ended audio sources. Set bits L1_INSEL = 1 and L2_INSEL
= 0 to use the RIN+ and LIN+ inputs. Set L1 _INSEL = 0 and
L2_INSEL = 1 to use the RIN- and LIN- inputs. Set L1_INSEL
= L2_INSEL = 1 to use both input pairs. Table 4 shows the
single ended input combinations.
202001c9
FIGURE 6. Single-Ended Input Configuration
TABLE 4. Single-Ended Stereo Input Modes
INPUT MODE L1_INSEL L2_INSEL INPUT DESCRIPTION
0 0 0 Fully Differential Input Mode
1 0 1 Single-ended input. RIN- and LIN- selected
2 1 0 Single-ended input. RIN+ and LIN+ selected
3 1 1 Single-ended input. RIN+ mixed with RIN- and LIN+ mixed with LIN-
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LM4949
Input Mixer / Multiplexer
The LM4949 includes a comprehensive mixer/multiplexer
controlled through the I2C interface. The mixer/multiplexer
allows any input combination to appear on any output of the
LM4949. Control bits LSR_SSEL and LSL_SSEL (loudspeak-
ers), and HPR_SSEL and HPL_SSEL (headphones) select
the individual stereo input channels; for example, LSR_SSEL
= 1 outputs the right channel stereo input on the right channel
loudspeaker, while LSL_SSEL = 1 outputs the left channel
stereo input on the left channel loudspeaker. Control bits
LSR_MSEL and LSL_MSEL (loudspeaker), and HPR_MSEL
and HPR_LSEL (headphones) direct the mono input to the
selected output. Setting HPR_MSEL = 1 outputs the mono
input on the right channel headphone. Control bits LS_XSEL
(loudspeaker) and HP_XSEL (headphone) selects both
stereo input channels and directs the signals to the opposite
outputs, for example, LS_XSEL = 1 outputs the right channel
stereo input on the left channel loudspeaker, while the left
channel stereo input is output on the right channel loudspeak-
er. Setting __XSEL = selects both stereo inputs simultane-
ously, unlike the __SSEL controls which select the stereo
input channels individually.
Multiple input paths can be selected simultaneously. Under
these conditions, the selected inputs are mixed together and
output on the selected channel. Tables 5 and 6 show how the
input signals are mixed together for each possible input se-
lection combination.
TABLE 5. Loudspeaker Multiplexer Control
LS MODE LS_XSEL LSR_MSEL/
LSL_MSEL
LSR_SSEL/
LSL_SSEL
LEFT CHANNEL OUTPUT RIGHT CHANNEL OUTPUT
0 0 0 MUTE MUTE
1 0 1 0 MONO MONO
2 0 0 1 LEFT (DIFF)/ /LIN+/LIN-/ (LIN+
- LIN-)
RIGHT (DIFF)/ /RIN+/RIN-/
(RIN+ - RIN-)
3 0 1 1 MONO + LEFT (DIFF)/ /LIN+/
LIN-/ (LIN+ - LIN-)
MONO + RIGHT (DIFF)/ /RIN+/
RIN-/ (RIN+ - RIN-)
4 1 0 1 LEFT (DIFF)/ /LIN+/LIN-/ (LIN+
- LIN-) + RIGHT (DIFF)/ /RIN+/
RIN-/ (RIN+ - RIN-)
LEFT (DIFF)/ /LIN+/LIN-/ (LIN+
- LIN-) + RIGHT (DIFF)/ /RIN+/
RIN-/ (RIN+ - RIN-)
5 1 1 1 MONO + LEFT (DIFF)/ /LIN+/
LIN-/ (LIN+ - LIN-) + RIGHT
(DIFF)/ /RIN+/RIN-/ (RIN+ -
RIN-)
MONO + LEFT (DIFF)/ /LIN+/
LIN-/ (LIN+ - LIN-) + RIGHT
(DIFF)/ /RIN+/RIN-/ (RIN+ -
RIN-)
TABLE 6. Headphone Multiplexer Control
HP MODE HP_XSEL HPR_MSEL/
HPL_MSEL
HPR_SSEL/
LSL_SSEL
LEFT CHANNEL OUTPUT RIGHT CHANNEL OUTPUT
0 0 0 MUTE MUTE
1 0 1 0 MONO MONO
2 0 0 1 LEFT (DIFF)/ /LIN+/LIN-/ (LIN
+ - LIN-)
RIGHT (DIFF)/ /RIN+/RIN-/
(RIN+ - RIN-)
3 0 1 1 MONO + LEFT (DIFF)/ /LIN+/
LIN-/ (LIN+ - LIN-)
MONO + RIGHT (DIFF)/ /RIN
+/RIN-/ (RIN+ - RIN-)
4 1 0 1 LEFT (DIFF)/ /LIN+/LIN-/ (LIN
+ - LIN-) + RIGHT (DIFF)/ /
RIN+/RIN-/ (RIN+ - RIN-)
LEFT (DIFF)/ /LIN+/LIN-/ (LIN
+ - LIN-) + RIGHT (DIFF)/ /RIN
+/RIN-/ (RIN+ - RIN-)
5 1 1 1 MONO + LEFT (DIFF)/ /LIN+/
LIN-/ (LIN+ - LIN-) + RIGHT
(DIFF)/ /RIN+/RIN-/ (RIN+ -
RIN-)
MONO + LEFT (DIFF)/ /LIN+/
LIN-/ (LIN+ - LIN-) + RIGHT
(DIFF)/ /RIN+/RIN-/ (RIN+ -
RIN-)
Power Supplies
The LM4949 uses different supplies for each portion of the
device, allowing for the optimum combination of headroom,
power dissipation and noise immunity. The speaker amplifier
gain stage is powered from VDD, while the output stage is
powered from VDDLS. The headphone amplifiers, input am-
plifiers and volume control stages are powered from VDDHP.
The separate power supplies allow the speakers to operate
from a higher voltage for maximum headroom, while the
headphones operate from a lower voltage, improving power
dissipation. VDDHP may be driven by a linear regulator to
further improve performance in noisy environments. The I2C
portion if powered from I2CVDD, allowing the I2C portion of
the LM4949 to interface with lower voltage digital controllers.
Shutdown Function
The LM4949 features five shutdown modes, configured
through the I2C interface. Bit D0 (PWR_ON) in the Shutdown
Control register shuts down/turns on the entire device. Set
PWR_ON = 1 to enable the LM4949, set PWR_ON 0 to dis-
able the device. Bits D0 – D3 in the Output On/Off Control
35 www.national.com
LM4949
shutdown/turn on the individual channels. HPR_ON (D3) con-
trols the right channel headphone output, HPL_ON (D2) con-
trols the left channel headphone output, LSR_ON (D1)
controls the right channel loudspeaker output, and LRL_ON
(D0) controls the left channel loudspeaker output. The
PWR_ON bit takes precedence over the individual channel
controls.
Audio Amplifier Gain Setting
The each channel of the LM4949 has two separate gain
stages. Each input stage features a 32 step volume control
with a range of -57dB to +18dB (Table 7). Each speaker out-
put stage has 4 gain settings (Table 8); 0dB, 2dB, 4dB, and
6dB when either a fully differential signal or two single ended
signals are applied on the _IN+ and _IN- pins; and 6dB, 8dB,
10dB and 12dB in single-ended input mode with only one sig-
nal applied. The headphone gain is not affected by the input
mode. Each headphone output stage has 3 gain settings (Ta-
ble 9), 0dB, -6dB, and -12dB. This allows for a maximum
separation of 24dB between the speaker and headphone out-
puts when both are active.
Calculate the total gain of a given signal path as follows:
AVOL + AOS = ATOTAL
Where AVOL is the volume control level, AOS is the gain setting
of the output stage, and ATOTAL is the total gain for the signal
path.
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LM4949
TABLE 7. 32 Step Volume Control
Volume Step MG4/LG4/RG4 MG3/LG3/RG3 MG2/LG2/RG2 MG1/LG1/RG1 MG0/LG0/RG0 Gain (dB)
1 0 0 0 0 0 –57
2 0 0 0 0 1 –49
3 0 0 0 1 0 –42
4 0 0 0 1 1 –34.5
5 0 0 1 0 0 –30.5
6 0 0 1 0 1 –27
7 0 0 1 1 0 –24
8 0 0 1 1 1 –21
9 0 1 0 0 0 –18
10 0 1 0 0 1 –15
11 0 1 0 1 0 –13.5
12 0 1 0 1 1 –12
13 0 1 1 0 0 –10.5
14 0 1 1 0 1 –9
15 0 1 1 1 0 –7.5
16 0 1 1 1 1 –6
17 1 0 0 0 0 –4.5
18 1 0 0 0 1 –3
19 1 0 0 1 0 –1.5
20 1 0 0 1 1 0
21 1 0 1 0 0 1.5
22 1 0 1 0 1 3
23 1 0 1 1 0 4.5
24 1 0 1 1 1 6
25 1 1 0 0 0 7.5
26 1 1 0 0 1 9
27 1 1 0 1 0 10.5
28 1 1 0 1 1 12
29 1 1 1 0 0 13.5
30 1 1 1 0 1 15
31 1 1 1 1 0 16.5
32 1 1 1 1 1 18
TABLE 8. Loudspeaker Gain Setting
LSRG1/LSLG1 LSRG0/LSLG0 Gain (dB)
_IN+ ≠ _IN- _IN+ =_IN-
0 0 12 6
0 1 10 4
1 0 8 2
1 1 6 0
TABLE 9. Headphone Gain Setting
HPG1 HPG0 Gain (dB)
0 0 0
0 1 –6
1 0 –12
37 www.national.com
LM4949
Differential Audio Amplifier Configuration
As logic supply voltages continue to shrink, system designers
increasingly turn to differential signal handling to preserve
signal to noise ratio with decreasing voltage swing. The
LM4949 can be configured as a fully differential amplifier,
amplifying the difference between the two inputs. The advan-
tage of the differential architecture is any signal component
that is common to both inputs is rejected, improving common-
mode rejection (CMRR) and increasing the SNR of the am-
plifier by 6dB over a single-ended architecture. The improved
CMRR and SNR of a differential amplifier reduce sensitivity
to ground offset related noise injection, especially important
in noisy applications such as cellular phones. Driving the
LM4949 differentially also allows the inputs to be DC coupled,
eliminating two external capacitors per channel. Set bits
L1_INSEL and L2_INSEL = 0 for differential input mode. The
left and right stereo inputs have selectable differential or sin-
gle-ended input modes, while the mono input is always dif-
ferential.
Single-Ended Audio Amplifier Configuration
In single-ended input mode, the audio sources must be ca-
pacitively coupled to the LM4949. With LIN+ ≠ LIN- and RIN
+ ≠ RIN-, the loud speaker gain is 6dB more than in differential
input mode, or when LIN+ = LIN- and RIN+ = RIN-. The head-
phone gain does not change. The mono input channel is not
affected by L1_INSEL and L2_INSEL, and is always config-
ured as a differential input.
Power Dissipation and Efficiency
The major benefit of Class D amplifiers is increased efficiency
versus Class AB. The efficiency of the LM4949 speaker am-
plifiers is attributed to the output transistors’ region of opera-
tion. The Class D output stage acts as current steering
switches, consuming negligible amounts of power compared
to their Class AB counterparts. Most of the power loss asso-
ciated with the output stage is due to the IR loss of the
MOSFET on-resistance, along with the switching losses due
to gate charge.
The maximum power dissipation per headphone channel in
Capacitor-Coupled mode is given by:
PDMAX = VDD2 / 2π2RL
In OCL mode, the maximum power dissipation per head-
phone channel increases due to the use of a third amplifier as
a buffer. The power dissipation is given by:
PDMAX = VDD2 / π2RL
PROPER SELECTION OF EXTERNAL COMPONENTS
Audio Amplifier Power Supply Bypassing / Filtering
Proper power supply bypassing is critical for low noise per-
formance and high PSRR. Place the supply bypass capaci-
tors as close to the device as possible. Typical applications
employ a voltage regulator with 10µF and 0.1µF bypass ca-
pacitors that increase supply stability. These capacitors do
not eliminate the need for bypassing of the LM4949 supply
pins. A 1µF ceramic capacitor placed close to each supply pin
is recommended.
Bypass Capacitor Selection
The LM4949 generates a VDD/2 common-mode bias voltage
internally. The BYPASS capacitor, CB, improves PSRR and
THD+N by reducing noise at the BYPASS node. Use a 1µF
capacitor, placed as close to the device as possible for CB.
Audio Amplifier Input Capacitor Selection
Input capacitors, CIN, in conjunction with the input impedance
of the LM4949 forms a high pass filter that removes the DC
bias from an incoming signal. The AC-coupling capacitor al-
lows the amplifier to bias the signal to an optimal DC level.
Assuming zero source impedance, the -3dB point of the high
pass filter is given by:
f-3dB = 1 / 2πRINCIN
Choose CIN such that f-3dB is well below the lowest frequency
of interest. Setting f-3dB too high affects the low-frequency re-
sponse of the amplifier. Use capacitors with low voltage co-
efficient dielectrics, such as tantalum or aluminum electrolyt-
ic. Capacitors with high-voltage coefficients, such as
ceramics, may result in increased distortion at low frequen-
cies. Other factors to consider when designing the input filter
include the constraints of the overall system. Although high
fidelity audio requires a flat frequency response between
20Hz and 20kHz, portable devices such as cell phones may
only concentrate on the frequency range of the spoken human
voice (typically 300Hz to 4kHz). In addition, the physical size
of the speakers used in such portable devices limits the low
frequency response; in this case, frequencies below 150Hz
may be filtered out.
PCB LAYOUT GUIDELINES
Minimize trace impedance of the power, ground and all output
traces for optimum performance. Voltage loss due to trace
resistance between the LM4949 and the load results in de-
creased output power and efficiency. Trace resistance be-
tween the power supply and GND of the LM4949 has the
same effect as a poorly regulated supply, increased ripple and
reduced peak output power. Use wide traces for power-sup-
ply inputs and amplifier outputs to minimize losses due to
trace resistance, as well as route heat away from the device.
Proper grounding improves audio performance, minimizes
crosstalk between channels and prevents switching noise
from interfering with the audio signal. Use of power and
ground planes is recommended.
Place all digital components and digital signal traces as far as
possible from analog components and traces. Do not run dig-
ital and analog traces in parallel on the same PCB layer.
www.national.com 38
LM4949
Revision History
Rev Date Description
1.0 09/06/06 Initial release.
1.1 09/27/06 Fixed some of the Typical Performance Curves.
1.2 01/17/07 Added the X1, X2, and X3 numerical values of theTLA25JJA mktg outline (back
page).
39 www.national.com
LM4949
Physical Dimensions inches (millimeters) unless otherwise noted
micro SMD Package
Order Number LM4949TL
NS Package Number TLA25JJA
X1 = 2.722, X2 = 2.722, X3 = 0.600
www.national.com 40
LM4949
Notes
41 www.national.com
LM4949
Notes
LM4949 Stereo Class D Audio Subsystem with OCL Headphone Amplifier
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