NSC LM4949_07

LM4949 Stereo Class D Audio Subsystem with OCL Headphone
Amplifier
General Description
Key Specifications
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 Capacitor-less (OCL) architecture that eliminates the output coupling
capacitors required by traditional headphone amplifiers. Additionally, the headphone amplifiers can be configured with
capacitively coupled (CC)loads, or used to drive an external
headphone amplifier. When configured for an external amplifier, the VDD/2 output (VOC) controls the external amplifier’s
shutdown input.
For improved noise immunity, the LM4949 features fully differential left, right and mono inputs. The three inputs can be
mixed/multiplexed to either the speaker or headphone amplifiers. The left and right inputs can be used as separate singleended 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. Superior click and pop suppression eliminates audible transients
on power-up/down and during shutdown.
■ Efficiency VDD = 3.6V, 400mW
into 8Ω
86.5%
■ Efficiency VDD = 5V, 1W into 8Ω
87.4%
■ 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
January 2007
LM4949
Typical Application
202001c6
FIGURE 1. Typical Audio Amplifier Application Circuit
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2
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
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LM4949
Thermal Resistance
Absolute Maximum Ratings (Note 2)
θJA
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (Note 1)
Storage Temperature
Input Voltage
Power Dissipation (Note 3)
ESD Susceptibility (Note 4)
ESD Susceptibility (Note 5)
Junction Temperature
35.1°C/W
Operating Ratings
Temperature Range
6.0V
−65°C to +150°C
−0.3V to VDD +0.3V
Internally Limited
2000V
200V
150°C
TMIN ≤ TA ≤ TMAX
Supply Voltage (VDD, VDDLS,
VDDHP)
I2C Voltage (I2CVDD)
−40°C ≤ TA ≤ +85°C
2.7V ≤ VDD≤ 5.5V
2.4V ≤ I2CVDD≤ 5.5V
Electrical Characteristics VDD = 3.0V
(SP)
(Notes 1, 2) The following specifications apply for AV = 0dB, RL
= 15μH + 8Ω + 15μH, RL(HP) = 32Ω, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C.
LM4949
Symbol
IDD
ISD
VOS
Parameter
Supply Current
Conditions
(Notes 7, 8)
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
Speaker (mode 1)
OCL HP (mode 1)
RL = 4Ω, THD+N = 1%
RL = 8Ω, THD+N = 10%
RL = 8Ω, THD+N = 1%
OCP HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
Output Power
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
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%
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Units
(Limits)
(Note 6)
LS Mode, f = 1 kHz
RL = 4Ω, THD+N = 10%
POUT
Limit
LS Mode
Stereo
Mono
Shutdown Supply Current
Output Offset Voltage
Typical
4
mA
0.03
2
µA (max)
8.9
5.6
48.9
24.5
mV (max)
mV (max)
340
mW
mW
mW
mW (min)
820
662
515
415
62.5
50
37.5
30.3
mW
mW
mW
mW
63
50
38
30
mW
mW
mW
mW (min)
Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Notes 7, 8)
Units
(Limits)
Differential Mode, f = 1kHz
THD+N
Total Harmonic Distortion + Noise
HP Mode, RL = 16Ω, POUT = 35mW
OCL
CC
0.015
0.012
%
%
HP Mode, RL = 32Ω, POUT = 20mW
OCL
CC
0.017
0.018
%
%
0.023
0.02
%
%
HP Mode, RL = 16Ω, POUT = 35mW
OCL
CC
0.023
0.017
%
%
HP Mode, RL = 32Ω, POUT = 20mW
OCL
CC
0.019
0.013
%
%
0.05
0.03
%
%
LS Mode
RL = 4Ω, POUT = 300mW
RL = 8Ω, POUT = 150mW
Single-Ended Input Mode, f = 1kHz
THD+N
Total Harmonic Distortion + Noise
LS Mode
RL = 4Ω, POUT = 300mW
RL = 8Ω, POUT = 150mW
Differential Input, A-weighted, Input Referred
eN
η
Noise
Efficiency
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
LS Mode, POUT = 400mW, RL = 8Ω
85.3
%
84.7
dB
LS Mode, f = 1kHz, RL = 8Ω, VIN = 1VP-P
Xtalk
Crosstalk
Differential Input Mode
OCL HP Mode, f = 1kHz, RL = 32Ω, VIN = 1VP-P
Differential Input Mode
68
dB
68
14
29
ms
ms
ms
TON
Turn on Time
CC Mode
OCL Mode
LS Mode
TOFF
Turn off Time
From any mode
683
ms
Input Impedance
Maximum Gain
Minimum Gain
24.8
222.7
kΩ
kΩ
ZIN
5
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LM4949
LM4949
LM4949
LM4949
Symbol
Parameter
Conditions
Volume Control
Minimum Gain
Maximum Gain
Typical
Limit
(Note 6)
(Notes 7, 8)
Units
(Limits)
–57
18
dB
dB
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
0
-6
-12
dB
dB
dB
Speaker Mode
–103
dB
Headphone Mode
–123
dB
Speaker Mode, f = 1kHz,
VIN = 200mVP-P
66.1
dB
70
dB
LS Second Gain Stage
AV
Gain
HP Second Gain Stage
Step 0
Step 1
Step 2
Mute
CMRR
Mute Attenuation
Common Mode Rejection Ratio
OCL Headphone Mode, f = 1kHz,
VIN = 200mVP-P
Differential Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
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
Single-Ended Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
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
All Inputs ON, Single-Ended Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
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OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 1kHz
6
66.1
70.5
65.4
72.2
dB
dB
dB
dB
(Notes 1, 2) The following specifications apply for AV = 0dB, RL
=
15μH
+
8Ω
+
15μH,
R
=
32Ω,
f
=
1kHz
unless
otherwise
specified. Limits apply for TA = 25°C.
(SP)
L(HP)
LM4949
Symbol
IDD
Supply Current
ISD
Shutdown Supply Current
VOS
Output Offset Voltage
Limit
(Note 6)
(Notes 7, 8)
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
0.03
1
µA (max)
6.7
8.9
20
49
mV (max)
mV (max)
Conditions
Headphone
Speaker
LS Mode, f = 1 kHz
RL = 4Ω, THD+N = 10%
W
W
W
W
94
76
55
45
mW
mW
mW
mW
93
75
56
45
mW
mW
mW
mW
HP Mode, RL = 16Ω, POUT = 50mW
OCL
CC
0.021
0.021
%
%
HP Mode, RL = 32Ω,
POUT = 30mW
OCL
CC
0.01
0.01
%
%
0.023
0.02
%
%
RL = 8Ω, THD+N = 10%
RL = 8Ω, THD+N = 1%
OCL HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
Output Power
mA
1.24
1
0.765
0.615
RL = 4Ω, THD+N = 1%
POUT
Units
(Limits)
Typical
Parameter
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
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%
Differential Mode, f = 1kHz
THD+N
Total Harmonic Distortion + Noise
LS Mode
RL = 4Ω, POUT = 400mW
RL = 8Ω, POUT = 300mW
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LM4949
Electrical Characteristics VDD = 3.6V
LM4949
LM4949
Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Notes 7, 8)
Units
(Limits)
Single-Ended Input Mode, f = 1kHz
THD+N
Total Harmonic Distortion + Noise
HP Mode, RL = 16Ω, POUT = 50mW
OCL
CC
0.021
0.017
%
%
HP Mode, RL = 32Ω, POUT = 30mW
OCL
CC
0.02
0.015
%
%
0.05
0.034
%
%
LS Mode
RL = 4Ω, POUT = 400mW
RL = 8Ω, POUT = 300mW
Differential Mode, A-weighted, Input Referred
eN
η
Noise
Efficiency
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
LS Mode, POUT = 400mW, RL = 8Ω
86.5
%
86
dB
LS Mode, f = 1kHz, RL = 8Ω, VIN = 1VP-P
Xtalk
Crosstalk
Differential Input Mode
OCL HP Mode, f = 1kHz, RL = 32Ω, VIN = 1VP-P
Differential Input Mode
68
dB
75
14
31
ms
ms
TON
Turn on Time
CC Mode
OCL Mode
LS Mode
TOFF
Turn off Time
From any mode
692
ms
Input Impedance
Maximum Gain
Minimum Gain
24.8
222.7
kΩ
kΩ
ZIN
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8
Symbol
Parameter
Conditions
Volume Control
Minimum Gain
Maximum Gain
Typical
Limit
(Note 6)
(Notes 7, 8)
Units
(Limits)
–57
18
dB
dB
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
0
–6
–12
dB
dB
Speaker Mode
–84
dB
Headphone Mode
–95
dB
Speaker Mode, f = 1kHz,
VIN = 200mVP-P
66
dB
68.6
dB
LS Second Gain Stage
AV
Gain
HP Second Gain Stage
Step 0
Step 1
Step 2
Mute
CMRR
Mute Attenuation
Common Mode Rejection Ratio
OCL Headphone Mode, f = 1kHz,
VIN = 200mVP-P
Differential Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
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
Single-Ended Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
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
All Inputs ON, Single-Ended Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
OCL HP Mode, f = 217Hz
OCL HP Mode, f = 1kHz
LS Mode, f = 217Hz
LS Mode, f = 1kHz
9
72
70
60
65
dB
dB
dB
dB
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LM4949
LM4949
LM4949
Electrical Characteristics VDD = 5.0V
(Notes 1, 2) The following specifications apply for AV = 0dB, RL
=
15μH
+
8Ω
+
15μH,
R
=
32Ω,
f
=
1kHz
unless
otherwise
specified. Limits apply for TA = 25°C.
(SP)
L(HP)
LM4949
Symbol
IDD
Supply Current
Limit
(Note 6)
(Notes 7, 8)
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)
0.1
1
µA (max)
10
9.6
52
50
mV (max)
mV (max)
Conditions
Stereo LS + HP Mode
ISD
Shutdown Supply Current
VOS
Output Offset Voltage
Headphone
Speaker
LS Mode, f = 1 kHz
RL = 4Ω, THD+N = 10%
mA
W
W
W
W
190
154
109
89
mW
mW
mW
mW
188
153
105
88
mW
mW
mW
mW
HP Mode, RL = 16Ω, POUT = 100mW
OCL
CC
0.02
0.027
%
%
HP Mode, RL = 32Ω, POUT = 50mW
OCL
CC
0.02
0.022
%
%
0.022
0.02
%
%
RL = 8Ω, THD+N = 10%
RL = 8Ω, THD+N = 1%
OCL HP Mode, f = 1 kHz
RL = 16Ω, THD+N = 10%
Output Power
13
2.5
2.01
1.48
1.19
RL = 4Ω, THD+N = 1%
POUT
Units
(Limits)
Typical
Parameter
RL = 16Ω, THD+N = 1%
RL = 32Ω, THD+N = 10%
RL = 32Ω, THD+N = 1%
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%
Differential Input Mode, f = 1kHz
THD + N
Total Harmonic Distortion + Noise
LS Mode
RL = 4Ω, POUT = 1W
RL = 8Ω, POUT = 600mW
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Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Notes 7, 8)
Units
(Limits)
Single-Ended Input Mode, f = 1kHz
THD + N
Total Harmonic Distortion + Noise
HP Mode, RL = 16Ω, POUT = 100mW
OCL
CC
0.021
0.02
%
%
HP Mode, RL = 32Ω, POUT = 50mW
OCL
CC
0.02
0.017
%
%
0.05
0.033
%
%
LS Mode
RL = 4Ω, POUT = 1W
RL = 8Ω, POUT = 600mW
Differential Input, A-weighted, Input Referred
eN
η
Noise
Efficiency
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
LS Mode, POUT = 1W, RL = 8Ω
87.4
%
105.8
dB
LS Mode, f = 1kHz, RL = 8Ω, VIN = 1VP-P
Xtalk
Crosstalk
Differential Input Mode
OCL HP Mode, f = 1kHz, RL = 32Ω, VIN = 1VP-P
Differential Input Mode
TON
TOFF
ZIN
69.6
dB
89
14
35
ms
ms
ms
Turn on Time
CC Mode
OCL Mode
LS Mode
Turn off Time
From any mode
716
ms
Input Impedance
Maximum Gain
Minimum Gain
24.8
222.7
kΩ
kΩ
11
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LM4949
LM4949
LM4949
LM4949
Symbol
Parameter
Conditions
Typical
Limit
(Note 6)
(Notes 7, 8)
Volume Control
Minimum Gain
Maximum Gain
Units
(Limits)
–57
18
dB
dB
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
0
–6
–12
dB
dB
dB
LS Second Gain Stage
AV
Gain
HP Second Gain Stage
Step 0
Step 1
Step 2
Mute
CMRR
Mute Attenuation
Common Mode Rejection Ratio
Speaker Mode
–102.7
dB
Headphone Mode
–123
dB
Speaker Mode, f = 1kHz,
VIN = 200mVP-P
64.4
dB
OCL Headphone Mode, f = 1kHz,
VIN = 200mVP-P
74.3
dB
Differential Input Mode, VRIPPLE = 200mVP-P
OCL HP Mode, f = 217Hz
PSRR
Power Supply Rejection Ratio
68.3
dB
OCL HP Mode, f = 1kHz
67.9
dB
LS Mode, f = 217Hz
73.8
dB
72
dB
LS Mode, f = 1kHz
Single-Ended Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
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
All Inputs ON, Single-Ended Input Mode, VRIPPLE = 200mVP-P
PSRR
Power Supply Rejection Ratio
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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
12
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
Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.
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
B1
VDDLS
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
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
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Right Channel Headphone Output
Speaker Power Supply
Speaker Ground
Mid-rail Bias Bypass
14
LM4949
Typical Performance Characteristics
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.0V, POUT = 300mW, RL = 4Ω
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, POUT = 400mW, RL = 4Ω
202001f0
202001f1
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 5.0V, POUT = 1W, RL = 4Ω
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.0V, POUT = 150mW, RL = 8Ω
202001f2
202001f3
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, POUT = 300mW, RL = 8Ω
THD+N vs Frequency
Speaker Mode, Differential Input
VDD = 5.0V, POUT = 600mW, RL = 8Ω
202001f4
202001f5
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LM4949
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.0V, POUT = 300mW, RL = 4Ω
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.6V, POUT = 400mW, RL = 4Ω
202001f6
202001f7
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 5.0V, POUT = 1W, RL = 4Ω
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.0V, POUT = 150mW, RL = 8Ω
202001f8
202001f9
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 3.6V, POUT = 300mW, RL = 8Ω
THD+N vs Frequency
Speaker Mode, Single-Ended Input
VDD = 5.0V, POUT = 600mW, RL = 8Ω
202001g1
202001g0
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16
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001g2
202001g3
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001g4
202001g5
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001g6
202001g7
17
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LM4949
THD+N vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
LM4949
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001g8
202001g9
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001h0
202001h1
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
THD+N vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001h2
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202001h3
18
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001h4
202001h5
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001h6
202001h7
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001h8
202001h9
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LM4949
THD+N vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
LM4949
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 35mW, RL = 16Ω
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 50mW, RL = 16Ω
202001i3
202001i4
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 100mW, RL = 16Ω
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.0V, POUT = 20mW, RL = 32Ω
202001i5
202001i6
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.6V, POUT = 30mW, RL = 32Ω
THD+N vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 5.0V, POUT = 50mW, RL = 32Ω
202001i7
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202001i8
20
LM4949
THD+N vs Output Power
Speaker Mode, Differential Input
AV = 6dB, RL = 4Ω, f = 1kHz
THD+N vs Output Power
Speaker Mode, Differential Input
AV = 6dB, RL = 8Ω, f = 1kHz
202001d1
202001d0
THD+N vs Output Power
Speaker Mode, Single-Ended Input
AV = 6dB, RL = 4Ω, f = 1kHz
THD+N vs Output Power
Speaker Mode, Single-Ended Input
AV = 6dB, RL = 8Ω, f = 1kHz
202001d2
202001d3
THD+N vs Output Power
OCL Headphone Mode, Differential Input
AV = 0dB, RL = 16Ω, f = 1kHz
THD+N vs Output Power
OCL Headphone Mode, Differential Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001d5
202001d4
21
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LM4949
THD+N vs Output Power
OCL Headphone Mode, Single-Ended Input
AV = 0dB, RL = 16Ω, f = 1kHz
THD+N vs Output Power
OCL Headphone Mode, Single-Ended Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001d6
202001d7
THD+N vs Output Power
CC Headphone Mode, Differential Input
AV = 0dB, RL = 16Ω, f = 1kHz
THD+N vs Output Power
CC Headphone Mode, Differential Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001d8
202001d9
THD+N vs Output Power
CC Headphone Mode, Single-Ended Input
AV = 0dB, RL = 16Ω, f = 1kHz
THD+N vs Output Power
CC Headphone Mode, Single-Ended Input
AV = 0dB, RL = 32Ω, f = 1kHz
202001e1
202001e0
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22
PSRR vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 8Ω
202001j0
202001i9
PSRR vs Frequency
Speaker Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 8Ω
PSRR vs Frequency
OCL Headphone Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j2
202001j1
PSRR vs Frequency
OCL Headphone Mode, Single-Ended Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
PSRR vs Frequency
OCL Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j3
202001j4
23
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LM4949
PSRR vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 8Ω
LM4949
PSRR vs Frequency
CC Headphone Mode, Differential Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
PSRR vs Frequency
CC Headphone Mode, Single-Ended Input
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
202001j6
202001j5
PSRR vs Frequency
CC Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, VRIPPLE = 200mVP-P, RL = 32Ω
Efficiency vs Output Power
Speaker Mode
RL = 32Ω, f = 1kHz
202001e2
202001j7
Efficiency vs Output Power
Speaker Mode
RL = 8Ω, f = 1kHz
Power Dissipation vs Output Power
Speaker Mode
RL = 4Ω, f = 1kHz
202001e3
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20200139
24
LM4949
Power Dissipation vs Output Power
Speaker Mode
RL = 8Ω, f = 1kHz
Power Dissipation vs Output Power
OCL Headphone Mode
RL = 16Ω, f = 1kHz
20200140
20200168
Power Dissipation vs Output Power
OCL Headphone Mode
RL = 32Ω, f = 1kHz
Power Dissipation vs Output Power
CC Headphone Mode
RL = 16Ω, f = 1kHz
20200169
20200195
Power Dissipation vs Output Power
CC Headphone Mode
RL = 32Ω, f = 1kHz
Output Power vs Supply Voltage
Speaker Mode
RL = 4Ω, f = 1kHz
202001e4
20200196
25
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LM4949
Output Power vs Supply Voltage
Speaker Mode
RL = 8Ω, f = 1kHz
Output Power vs Supply Voltage
OCL Headphone Mode
RL = 16Ω, f = 1kHz
202001e6
202001e5
Output Power vs Supply Voltage
OCL Headphone Mode
RL = 32Ω, f = 1kHz
Output Power vs Supply Voltage
CC Headphone Mode
RL = 16Ω, f = 1kHz
202001e7
202001e8
Output Power vs Supply Voltage
CC Headphone Mode
RL = 32Ω, f = 1kHz
CMRR vs Frequency
Speaker Mode, Differential Input
VDD = 3.6V, VCM = 1VP-P, RL = 8Ω, f = 1kHz
202001e9
202001j8
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26
LM4949
CMRR vs Frequency
OCL Headphone Mode
VDD = 3.6V, VCM = 1VP-P, RL = 32Ω
CMRR vs Frequency
CC Headphone Mode
VDD = 3.6V, VCM = 1VP-P, RL = 32Ω
202001j9
202001k3
Output Noise vs Frequency
Speaker Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, RL = 8Ω
Output Noise vs Frequency
OCL Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, RL = 32Ω
202001k0
202001k1
Output Noise vs Frequency
CC Headphone Mode, Single-Ended Input
Stereo and Mono Inputs Active
VDD = 3.6V, RL = 32Ω
Crosstalk vs Frequency
Speaker Mode
VDD = 3.6V, VRIPPLE = 1VP-P, RL = 8Ω
202001i0
202001k2
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LM4949
Crosstalk vs Frequency
OCL Headphone Mode
VDD = 3.6V, VRIPPLE = 1VP-P, RL = 32Ω
Crosstalk vs Frequency
CC Headphone Mode
VDD = 3.6V, VRIPPLE = 1VP-P, RL = 32Ω
202001i1
202001i2
Supply Current vs Supply Voltage
Speaker Mode, No Load
Supply Current vs Supply Voltage
OCL Headphone Mode, No Load
202001b1
202001b4
Supply Current vs Supply Voltage
CC Headphone Mode, No Load
Supply Current vs Supply Voltage
Speaker and OCL Headphone Mode, No Load
202001b8
202001b7
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28
LM4949
Supply Current vs Supply Voltage
Shutdown Mode, No Load
Turn-On
OCL Headphone Mode
20200113
202001b9
Turn-Off
OCL Headphone Mode
Turn-On
CC Headphone Mode
20200114
20200115
Turn-Off
CC Headphone Mode
20200116
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LM4949
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.
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 bidirectional (open-collector) although the LM4949 does not
TABLE 2. Device Address
ADR
A7
A6
A5
A4
A3
A2
A1
A0
X
1
1
1
1
1
0
X
0
0
1
1
1
1
1
0
0
0
1
1
1
1
1
1
0
1
0
is generated. If the LM4949 receives the address correctly,
then the LM4949 pulls the data line low, generating an acknowledge 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 acknowledgement of the data word, the master device issues a “stop”
bit, allowing SDA to go high while the clock signal is high.
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 significant 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
20200109
FIGURE 2. I2C Bus Format
20200110
FIGURE 3. I2C Timing Diagram
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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.
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LM4949
TABLE 3. I2C Control Registers
LM4949
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 frequency 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 potential 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.
GENERAL AMPLIFIER FUNCTION
Class D Amplifier
The LM4949 features a high-efficiency, filterless, Class D
stereo amplifier. The LM4949 Class D amplifiers feature a filterless 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. Because 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+ decreases. The difference between the two pulse widths yields the
differential output voltage.
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 amplifier 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:
Headphone Amplifier
The LM4949 headphone amplifier features three different operating modes, output capacitorless (OCL), capacitor-coupled (CC), and external amplifier mode.
The OCL architecture eliminates the bulky, expensive output
coupling capacitors required by traditional headphone amplifiers. 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-
f-3dB = 1 / 2πRLCOUT
Where RL is the headphone impedance, and COUT is the output 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
(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.
External Headphone Amplifier
The LM4949 features the ability to drive and control a separate 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
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LM4949
202001c8
FIGURE 5. Driving an External Headphone Amplifier
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LM4949
= 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.
Single-Ended Input
The left and right stereo inputs of the LM4949 can be configured for single-ended sources (Figure 6). In single-ended
input mode, the LM4949 can accept up to 4 different singleended audio sources. Set bits L1_INSEL = 1 and L2_INSEL
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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34
TABLE 5. Loudspeaker Multiplexer Control
LS MODE
LS_XSEL
0
LSR_MSEL/
LSL_MSEL
LSR_SSEL/
LSL_SSEL
LEFT CHANNEL OUTPUT
RIGHT CHANNEL OUTPUT
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+/ MONO + RIGHT (DIFF)/ /RIN+/
LIN-/ (LIN+ - LIN-)
RIN-/ (RIN+ - RIN-)
4
1
0
1
LEFT (DIFF)/ /LIN+/LIN-/ (LIN+ LEFT (DIFF)/ /LIN+/LIN-/ (LIN+
- LIN-) + RIGHT (DIFF)/ /RIN+/ - LIN-) + RIGHT (DIFF)/ /RIN+/
RIN-/ (RIN+ - 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
0
HPR_MSEL/
HPL_MSEL
HPR_SSEL/
LSL_SSEL
LEFT CHANNEL OUTPUT
RIGHT CHANNEL OUTPUT
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+/ MONO + RIGHT (DIFF)/ /RIN
LIN-/ (LIN+ - LIN-)
+/RIN-/ (RIN+ - RIN-)
4
1
0
1
LEFT (DIFF)/ /LIN+/LIN-/ (LIN LEFT (DIFF)/ /LIN+/LIN-/ (LIN
+ - LIN-) + RIGHT (DIFF)/ / + - LIN-) + RIGHT (DIFF)/ /RIN
RIN+/RIN-/ (RIN+ - RIN-)
+/RIN-/ (RIN+ - RIN-)
5
1
1
1
MONO + LEFT (DIFF)/ /LIN+/ MONO + LEFT (DIFF)/ /LIN+/
LIN-/ (LIN+ - LIN-) + RIGHT LIN-/ (LIN+ - LIN-) + RIGHT
(DIFF)/ /RIN+/RIN-/ (RIN+ (DIFF)/ /RIN+/RIN-/ (RIN+ RIN-)
RIN-)
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.
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 amplifiers 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
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 disable the device. Bits D0 – D3 in the Output On/Off Control
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LM4949
(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 loudspeaker. Setting __XSEL = selects both stereo inputs simultaneously, 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 selection combination.
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 (loudspeakers), 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
LM4949
shutdown/turn on the individual channels. HPR_ON (D3) controls the right channel headphone output, HPL_ON (D2) controls 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.
10dB and 12dB in single-ended input mode with only one signal applied. The headphone gain is not affected by the input
mode. Each headphone output stage has 3 gain settings (Table 9), 0dB, -6dB, and -12dB. This allows for a maximum
separation of 24dB between the speaker and headphone outputs when both are active.
Calculate the total gain of a given signal path as follows:
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 output 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,
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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.
36
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
0
Gain (dB)
_IN+ ≠ _IN-
_IN+ =_IN-
0
12
6
0
1
10
4
1
0
8
2
1
1
6
0
TABLE 9. Headphone Gain Setting
HPG1
HPG0
0
0
Gain (dB)
0
0
1
–6
1
0
–12
37
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LM4949
TABLE 7. 32 Step Volume Control
LM4949
tors as close to the device as possible. Typical applications
employ a voltage regulator with 10µF and 0.1µF bypass capacitors 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.
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 advantage of the differential architecture is any signal component
that is common to both inputs is rejected, improving commonmode rejection (CMRR) and increasing the SNR of the amplifier 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 single-ended input modes, while the mono input is always differential.
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 allows 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:
Single-Ended Audio Amplifier Configuration
In single-ended input mode, the audio sources must be capacitively 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 headphone gain does not change. The mono input channel is not
affected by L1_INSEL and L2_INSEL, and is always configured as a differential input.
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 response of the amplifier. Use capacitors with low voltage coefficient dielectrics, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as
ceramics, may result in increased distortion at low frequencies. 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.
Power Dissipation and Efficiency
The major benefit of Class D amplifiers is increased efficiency
versus Class AB. The efficiency of the LM4949 speaker amplifiers is attributed to the output transistors’ region of operation. 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 associated 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:
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 decreased output power and efficiency. Trace resistance between 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-supply 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 digital and analog traces in parallel on the same PCB layer.
PDMAX = VDD2 / 2π2RL
In OCL mode, the maximum power dissipation per headphone 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 performance and high PSRR. Place the supply bypass capaci-
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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
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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
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40
LM4949
Notes
41
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LM4949 Stereo Class D Audio Subsystem with OCL Headphone Amplifier
Notes
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