LM49270
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SNAS384B – DECEMBER 2006 – REVISED MARCH 2007
LM49270
Filterless 2.2W Stereo Class D Audio
Subsystem with OCL Headphone Amplifier, 3D Enhancement, and Headphone Sense
Check for Samples: LM49270
FEATURES
1
•
•
•
•
•
•
•
•
•
2
•
•
•
•
•
Stereo Filterless Class D Amplifier
Selectable OCL/CC Headphone Amplifier
Headphone Sense Ability
TI’s 3D Enhancement
RF Suppression
I2C Control Interface
32-Step Digital Volume Control
6 Operating Modes
Output Short Circuit Protection and Thermal
Shutdown Protection
Minimum External Components
Click and Pop Suppression
Micro-Power Shutdown
Independent Speaker and Headphone Volume
Controls
Available in Space-Saving 28 Pin WQFN
Package
APPLICATIONS
•
•
•
•
Portable DVD Players
Smart Phones
PDAs
Laptops
KEY SPECIFICATIONS
•
•
•
Stereo Class D Amplifier Efficiency:
– VDD = 3.3V, 450mW/Ch into 8Ω 84%
– VDD = 5V, 1W/Ch into 8Ω 84%
Quiescent Power Supply Current, VDD = 3.3V
– Speaker Mode 5.5 mA
– Headphone Mode (OCL) 4 mA
Power Output/Channel, VDD = 5V
– Class D Speaker Amplifier:
– RL = 4Ω, THD+N = ≤ 10% 2.3 W
– RL = 8Ω, THD+N = ≤ 1% 106 W
•
– Headphone Amplifier:
– RL = 16Ω, THD+N = ≤ 1% 155 mW
– RL = 32Ω, THD+N = ≤ 1% 90 mW
Shutdown Current 0.02μA
DESCRIPTION
The LM49270 is a fully integrated audio subsystem
designed for stereo multimedia applications. The
LM49270 combines a 2.2W stereo Class D amplifier
with a 155mW stereo headphone amplifier, volume
control, headphone sense, and TI’s unique 3D sound
enhancement into a single device. The LM49270
uses flexible I2C control interface for multiple
application requirements.
The filterless stereo class D amplifiers delivers
2.2W/channel into a 4Ω load with less than 10%
THD+N with a 5V supply. The headphone amplifier
features Output Capacitor-less (OCL) architecture
that eliminates the output coupling capacitors
required by traditional headphone amplifiers.
The IC features a headphone sense input (HPS) that
automatically detects the presence of a headphone
and configures the device accordingly. The LM49270
can automatically switch from OCL headphone output
to a line driver output. If the VOC pin is pulled to
GND, the VOC amplifier is disabled and the VOC pin
is internally set to GND. This feature allows the
LM49270 to be used as a line driver in OCL mode
without a GND conflict on the headphone jack sleeve.
Additionally, the headphone amplifier can be
configured as capacitively coupled (CC).
The LM49270 features a 32 step volume control for
the headphone and stereo outputs. The device mode
select and volume 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. The LM49270 is available in a
space saving 28-pin, 5x5mm WQFN package.
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006–2007, Texas Instruments Incorporated
LM49270
SNAS384B – DECEMBER 2006 – REVISED MARCH 2007
www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Typical Application
VDD
CS
CS
VDD
Audio Input
CIN
LSVDD
LSVDD
LIN
LLS+
L3DIN
LLS-
R3D
3D CONTROL
R3DADJ
LSGND
SPEAKER
VOLUME
CONTROL
C3D
RLS+
Audio Input
R3DIN
RLS-
CIN
RIN
HPS
LHP
CB
BYPASS
Bias
Click/Pop
Suppresion
I2CVDD
HEADPHONE
VOLUME
CONTROL
RHP
I2CVDD
SDA
I2C
BUS
VOC
I2C
Interface
SCL
HPVDD
ADR
GND
VIH
HPVDD
CS
VIL
Figure 1. Typical Audio Amplifier Application Circuit
2
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SNAS384B – DECEMBER 2006 – REVISED MARCH 2007
Connection Diagram
GND HPS
28
27
SCL SDA LSVDD LLS+ LLS26
25
24
23
22
RHP
1
21
NC
VOC
2
20
ADR
LHP
3
19
VDD
HPVDD
4
18
LSGND
R3DIN
5
17
I2CVDD
L3DIN
6
16
NC
BYPASS
7
15
NC
8
LIN
9
10
11
RIN GND
12
13
14
NC LSVDD RLS+ RLS-
Figure 2. WQFN Package
5mm x 5mm x 0.8mm
Top View
See Package Number RSG0028A
Pin Descriptions
PIN
NAME
1
RHP
Right channel headphone output
DESCRIPTION
2
VOC
VDD/2 buffer output
3
LHP
Left channel headphone output
4
HPVDD
Headphone supply input
5
R3DIN
Right channel 3D input
6
L3DIN
Left channel 3D input
7
BYPASS
8
LIN
Left channel input
Bias bypass
9
RIN
Right channel input
10
GND
Analog ground
11
NC
12
LSVDD
Speaker supply voltage input
13
RLS+
Right channel non-inverting speaker output
14
RLS-
Right channel inverting speaker output
15
NC
No connect
16
NC
No connect
17
I2CVDD
I2C supply voltage input
18
LSGND
Speaker ground
No connect
19
VDD
Power supply
20
ADR
Address
21
NC
No connect
22
LLS-
Left channel inverting speaker output
23
LLS+
Left channel non-inverting speaker output
24
LSVDD
Speaker supply voltage input
25
SDA
Serial data input
26
SCL
Serial clock input
27
HPS
Headphone sense input
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LM49270
SNAS384B – DECEMBER 2006 – REVISED MARCH 2007
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Pin Descriptions (continued)
PIN
NAME
28
GND
Absolute Maximum Ratings
Supply Voltage
DESCRIPTION
Headphone ground
(1) (2) (3)
(1)
6.0V
−65°C to +150°C
Storage Temperature
Input Voltage
–0.3V to VDD +0.3V
Power Dissipation
(4)
Internally Limited
ESD Susceptibility
(5)
2000V
ESD Susceptibility
(6)
200V
Junction Temperature (TJMAX)
θJA
Thermal Resistance
(1)
(2)
(3)
(4)
(5)
(6)
150°C
35.1°C/W
All voltages are measured with respect to the ground pin, unless otherwise specified.
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 ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which specify performance limits. This assumes that the device is within the Operating
Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device
performance.
If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications.
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 LM49270 see power derating currents for more information.
Human body model, 100pF discharged through a 1.5kΩ resistor.
Machine Model, 220pF–240pF discharged through all pins.
Operating Ratings
(1)
Temperature Range
TMIN ≤ TA ≤ TMAX
Supply Voltage
(VDD, LSVDD, HPVDD)
2.4V ≤ VDD ≤ 5.5V
I2C Voltage (I2CVDD)
(1)
4
−40°C ≤ TA ≤ 85°C
2.4V ≤ I2CVDD ≤ 5.5V
All voltages are measured with respect to the ground pin, unless otherwise specified.
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SNAS384B – DECEMBER 2006 – REVISED MARCH 2007
Electrical Characteristics VDD = 3.3V
(1)
The following specifications apply for Headphone: AV = 0dB, RL(HP) = 32Ω; for Loudspeakers: AV = 6dB, RL(SP) = 15μH + 8Ω
+ 15μH , f = 1kHz, unless otherwise specified. Limits apply for TA = 25°C.
Symbol
Parameter
IDD
Supply Current
ISD
Shutdown Supply Current
VOS
Output Offset Voltage
Conditions
VIN = 0, RL = No Load,
Both channels active
Speaker ON, HP OFF
Speaker OFF, CC HP ON
Speaker OFF, OCL HP ON
LM49270
Typical
5.5
3
4
(2)
Limit (3)
7.6
4.7
5.75
(4)
Units
(Limits)
mA (max)
mA (max)
mA (max)
0.02
2
μA (max)
10
10
25
60
mV (max)
mV (max)
THD+N = 1%
RL = 4Ω
RL = 8Ω
700
450
400
mW
mW (min)
THD+N = 10%
RL = 4Ω
RL = 8Ω
870
560
Headphone
Speaker
Speaker Mode, f = 1kHz
mW
mW
CC Headphone Mode, f = 1kHz
POUT
Output Power
THD+N = 1%
RL = 16Ω
RL = 32Ω
60
36
THD+N = 10%
RL = 16Ω
RL = 32Ω
74
55
30
mW
mW (min)
mW
mW
OCL Headphone Mode, f = 1kHz
THD+N
eN
Noise
η
Efficiency
Xtalk
(1)
(2)
(3)
(4)
Total Harmonic Distortion + Noise
Crosstalk
THD+N = 1%
RL = 16Ω
RL = 32Ω
60
36
THD+N = 10%
RL = 16Ω
RL = 32Ω
73
55
mW
mW
Speaker Mode, f = 1kHz
POUT = 100mW, RL = 8Ω
0.02
%
CC Headphone Mode,
f = 1kHz
POUT = 12mW, RL = 32Ω
0.015
%
OCL Headphone Mode,
f = 1kHz
POUT = 12mW, RL = 32Ω
0.02
%
Speaker Mode,
A-Wtg, Input Referred
47
μV
CC Headphone Mode,
A-Wtg, Input Referred
10
μV
OCL Headphone Mode, A-Wtg,
Input Referred
11
μV
Speaker Mode
RL = 8Ω
84
%
Speaker Mode,
f = 1kHz, VIN = 1Vp-p
71
dB
CC Headphone Mode,
f = 1kHz, VIN = 1Vp-p
70
dB
OCL Headphone Mode,
f = 1kHz, VIN = 1Vp-p
55
dB
30
mW
mW (min)
All voltages are measured with respect to the ground pin, unless otherwise specified.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to AOQL (Average Outgoing Quality Level).
Data sheet min and max specification limits are specified by design, test, or statistical analysis.
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LM49270
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Electrical Characteristics VDD = 3.3V (continued)
(1)
The following specifications apply for Headphone: AV = 0dB, RL(HP) = 32Ω; for Loudspeakers: AV = 6dB, RL(SP) = 15μH + 8Ω
+ 15μH , f = 1kHz, unless otherwise specified. Limits apply for TA = 25°C.
Symbol
Parameter
Conditions
LM49270
Typical
(2)
Limit (3)
(4)
Units
(Limits)
TON
Turn-on Time
30
ms
TOFF
Turn-off Time
64
ms
Maximum Gain
23.5
kΩ
Minimum Gain
210
kΩ
Maximum Gain, Speaker Mode
30
dB
Minimum Gain, Speaker Mode
–47
dB
Maximum Gain, Headphone Mode
18
dB
Minimum Gain, Headphone Mode
–59
dB
Speaker Mode,
VRIPPLE = 200mVp-p Sine
f = 217Hz
f = 1kHz
68
68
dB
dB
Headphone Mode,
VRIPPLE = 200mVp-p Sine, CC
Mode
f = 217Hz
f = 1kHz
73
73
dB
dB
Headphone Mode,
VRIPPLE = 200mVp-p Sine, OCL
Mode
f = 217Hz
f = 1kHz
75
79
dB
dB
ZIN
Input Impedance
AV
Gain
PSRR
Power Supply Rejection Ratio
HPS(Th)
Headphone Sense Threshold
Detect Headphone
2.9
V (min)
Detect no Headphone
1.8
V (max)
Electrical Characteristics VDD = 5.0V
(1)
The following specifications apply for Headphone” AV = 0dB, RL(HP) = 32Ω,: for Loudspeakers: AV = 6dB, RL(SP) = 15μH + 8Ω
+ 15μH, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C.
Symbol
Parameter
IDD
Supply Current
ISD
Shutdown Supply Current
VOS
(1)
(2)
(3)
(4)
6
Output Offset Voltage
Conditions
VIN = 0, RL = No Load,
Both channels active
Speaker ON, HP OFF
Speaker OFF, CC HP ON
Speaker OFF, OCL HP ON
Headphone
Speaker
LM49270
Typical
8.5
3.6
4.7
(2)
Limit (3)
12.4
5.5
6.5
(4)
Units
(Limits)
mA (max)
mA (max)
mA (max)
0.15
2
μA (max)
10
10
25
60
mV (max)
mV (max)
All voltages are measured with respect to the ground pin, unless otherwise specified.
Typicals are measured at 25°C and represent the parametric norm.
Limits are specified to AOQL (Average Outgoing Quality Level).
Data sheet min and max specification limits are specified by design, test, or statistical analysis.
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SNAS384B – DECEMBER 2006 – REVISED MARCH 2007
Electrical Characteristics VDD = 5.0V (continued)
(1)
The following specifications apply for Headphone” AV = 0dB, RL(HP) = 32Ω,: for Loudspeakers: AV = 6dB, RL(SP) = 15μH +
8Ω + 15μH, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C.
Symbol
Parameter
Conditions
LM49270
Typical
(2)
Limit (3)
(4)
Units
(Limits)
Speaker Mode, f = 1kHz,
THD+N = 1%
RL = 4Ω
RL = 8Ω
1.75
1.06
W
W
THD+N = 10 %
RL = 4Ω
RL = 8Ω
2.2
1.35
W
W
THD+N = 1%
RL = 16Ω
RL = 32Ω
155
90
mW
mW
THD+N = 10%
RL = 16Ω
RL = 32Ω
177
140
mW
mW
THD+N = 1%
RL = 16Ω
RL = 32Ω
155
90
mW
mW
THD+N = 10%
RL = 16Ω
RL = 32Ω
175
140
mW
mW
Speaker Mode, f = 1kHz
POUT = 100mW, RL = 8Ω
0.03
%
CC Headphone Mode,
f = 1kHz
POUT = 12mW, RL = 32Ω
0.02
%
OCL Headphone Mode,
f = 1kHz
POUT = 12mW, RL = 32Ω
CC Headphone Mode, f = 1kHz,
POUT
Output Power
OCL Headphone Mode, f = 1kHz,
THD+N
eN
η
Xtalk
Total Harmonic Distortion + Noise
Noise
Efficiency
Crosstalk
TON
Turn-on Time
TOFF
Turn-off Time
ZIN
AV
Input Impedance
Gain
0.03
%
Speaker Mode,
A-Wtg, Input Referred
47
μV
CC Headphone Mode,
A-Wtg, Input Referred
10
μV
OCL Headphone Mode,
A-Wtg, Input Referred
11
μV
Speaker Mode
RL = 8Ω
84
%
Speaker Mode,
f = 1kHz, VIN = 1Vp-p
–85
dB
CC Headphone Mode,
f = 1kHz, VIN = 1Vp-p
–70
dB
OCL Headphone Mode,
f = 1kHz, VIN = 1Vp-p
–58
dB
43
ms
100
ms
Maximum Gain
23.5
kΩ
Minimum Gain
210
kΩ
Maximum Gain, Speaker Mode
30
dB
Minimum Gain, Speaker Mode
–47
dB
Maximum Gain, Headphone Mode
18
dB
Minimum Gain, Headphone Mode
–59
dB
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Electrical Characteristics VDD = 5.0V (continued)
(1)
The following specifications apply for Headphone” AV = 0dB, RL(HP) = 32Ω,: for Loudspeakers: AV = 6dB, RL(SP) = 15μH +
8Ω + 15μH, f = 1kHz unless otherwise specified. Limits apply for TA = 25°C.
Symbol
PSRR
Power Supply Rejection Ratio
HPS(Th)
8
Parameter
Headphone Sense Threshold
Conditions
LM49270
Typical
(2)
Limit (3)
(4)
Units
(Limits)
Speaker Mode,
VRIPPLE = 200mVp-p Sine
f = 217Hz
f = 1kHz
61
61
dB
dB
Headphone Mode,
VRIPPLE = 200mVp-p Sine, CC
Mode
f = 217Hz
f = 1kHz
75
74
dB
min
Headphone Mode,
VRIPPLE = 200mVp-p Sine, OCL
Mode
f = 217Hz
f = 1kHz
78
75
dB
dB
Detect Headphone
Detect no Headphone
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4.4
V (min)
3
V (max)
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Typical Performance Characteristics
100
THD+N
vs
Output Power
Speaker Mode
AV = 6dB, RL = 4Ω, f = 1kHz
100
THD+N
vs
Output Power
Speaker Mode
AV = 6dB, RL = 8Ω, f = 1kHz
VDD = 5V
VDD = 5V
10
10
THD+N (%)
THD+N (%)
VDD = 3.3V
1
0.1
VDD = 3.3V
1
0.1
0.01
0.001
0.001
0.1
0.01
1
0.01
0.001
10
OUTPUT POWER/CHANNEL (W)
100
Figure 4.
THD+N
vs
Output Power
OCL Headphone Mode
AV = 0dB, RL = 16Ω, f = 1kHz
THD+N
vs
Output Power
OCL Headphone Mode
AV = 0dB, RL = 32Ω, f = 1kHz
100
VDD = 5V
10
VDD = 5V
10
VDD = 3.3V
THD+N (%)
THD+N (%)
1
OUTPUT POWER/CHANNEL (W)
1
0.1
VDD = 3.3V
1
0.1
0.01
0.01m
100m
1m
10m
0.1m
OUTPUT POWER/CHANNEL (W)
0.01
0.01m
1
0.1m
1m
10m
100m
Figure 6.
THD+N
vs
Output Power
CC Headphone Mode
AV = 0dB, RL = 16Ω, f = 1kHz
THD+N
vs
Output Power
CC Headphone Mode
AV = 0dB, RL = 32Ω, f = 1kHz
100
VDD = 5V
VDD = 5V
10
VDD = 3.3V
THD+N (%)
VDD = 3.3V
1
0.1
0.01
0.01m
1
OUTPUT POWER/CHANNEL (W)
Figure 5.
10
THD+N (%)
0.1
Figure 3.
10
100
0.01
1
0.1
0.1m
1m
10m
100m
1
0.01
0.01m
0.1m
1m
10m
100m
1
OUTPUT POWER/CHANNEL (W)
OUTPUT POWER/CHANNEL (W)
Figure 7.
Figure 8.
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Typical Performance Characteristics (continued)
THD+N
vs
Frequency
Speaker Mode
VDD = 5V, POUT = 500mW, RL = 4Ω
100
100
10
10
THD+N (%)
THD+N (%)
THD+N
vs
Frequency
Speaker Mode
VDD = 3.3V, POUT = 300mW, RL = 4Ω
1
0.1
1k
0.001
20
10k 20k
1k
10k 20k
FREQUENCY (Hz)
Figure 9.
Figure 10.
THD+N
vs
Frequency
Speaker Mode
VDD = 3.3V, POUT = 200mW, RL = 8Ω
THD+N
vs
Frequency
Speaker Mode
VDD = 5V, POUT = 350mW, RL = 8Ω
100
100
10
10
1
0.1
0.001
20
1
0.1
0.01
100
1k
0.001
20
10k 20k
100
1k
10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 11.
Figure 12.
THD+N
vs
Frequency
OCL Headphone Mode
VDD = 3.3V, POUT = 45mW, RL = 16Ω
THD+N
vs
Frequency
OCL Headphone Mode
VDD = 5V, POUT = 100mW, RL = 16Ω
100
100
10
10
THD+N (%)
THD+N (%)
100
FREQUENCY (Hz)
THD+N (%)
THD+N (%)
100
0.01
1
0.1
0.001
20
1
0.1
0.01
0.01
100
1k
FREQUENCY (Hz)
10k 20k
0.001
20
100
1k
10k 20k
FREQUENCY (Hz)
Figure 13.
10
0.1
0.01
0.01
0.001
20
1
Figure 14.
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Typical Performance Characteristics (continued)
THD+N
vs
Frequency
OCL Headphone Mode
VDD = 5V, POUT = 70mW, RL = 32Ω
100
100
10
10
THD+N (%)
THD+N (%)
THD+N
vs
Frequency
OCL Headphone Mode
VDD = 3.3V, POUT = 25mW, RL = 32Ω
1
0.1
0.01
100
1k
0.001
20
10k 20k
100
1k
10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 15.
Figure 16.
THD+N
vs
Frequency
CC Headphone Mode
VDD = 3.3V, POUT = 45mW, RL = 16Ω
THD+N
vs
Frequency
CC Headphone Mode
VDD = 5V, POUT = 100mW, RL = 16Ω
100
100
10
10
1
0.1
0.01
0.001
20
1
0.1
0.01
100
1k
0.001
20
10k 20k
100
1k
10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 17.
Figure 18.
THD+N
vs
Frequency
CC Headphone Mode
VDD = 3.3V, POUT = 25mW, RL = 32Ω
THD+N
vs
Frequency
CC Headphone Mode
VDD = 5V, POUT = 70mW, RL = 32Ω
100
100
10
10
THD+N (%)
THD+N (%)
0.1
0.01
THD+N (%)
THD+N (%)
0.001
20
1
1
0.1
0.01
0.001
20
1
0.1
0.01
100
1k
10k 20k
0.001
20
100
1k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 19.
Figure 20.
10k 20k
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Typical Performance Characteristics (continued)
PSRR
vs
Frequency
Speaker Mode
VDD = 3.3V, VRIPPLE = 200mVP-P, RL = 8Ω
PSRR
vs
Frequency
OCL Headphone Mode
VDD = 3.3V, VRIPPLE = 200mVP-P, RL = 32Ω
0
-10
-10
-20
-20
-30
-30
PSRR (dB)
PSRR(dB)
0
-40
-50
-40
-50
-60
-60
-70
-70
-80
-80
20
100
1k
-90
20
10k 20k
100
1k
10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 21.
Figure 22.
PSRR
vs
Frequency
CC Headphone Mode
VDD = 3.3V, VRIPPLE = 200mVP-P, RL = 32Ω
Efficiency
vs
Output Power
Speaker Mode
RL = 4Ω, f = 1kHz
100
0
VDD = 5V
90
-10
80
EFFICIENCY (%)
PSRR (dB)
-20
-30
-40
-50
70
VDD = 3.3V
60
50
40
30
-60
20
-70
10
-80
20
100
1k
0
10k 20k
0
FREQUENCY (Hz)
100
3000
Figure 23.
Figure 24.
Efficiency
vs
Output Power
Speaker Mode
RL = 8Ω, f = 1kHz
Power Dissipation
vs
Output Power
Speaker Mode
RL = 4Ω, f = 1kHz
1250
POWER DISSIPATION (mW)
80
70
VDD = 5V
60
50
40
30
20
1000
4000
VDD = 5V
750
VDD = 3.3V
500
250
10
POUT = POUTL + POUTR
0
0
0
500
1000
1500
2000
0
1000
2000
3000
4000
OUTPUT POWER (mW)
OUTPUT POWER (mW)
Figure 25.
12
2000
OUTPUT POWER (mW)
VDD = 3.3V
90
EFFICIENCY (%)
1000
Figure 26.
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Typical Performance Characteristics (continued)
Power Dissipation
vs
Output Power
Speaker Mode
RL = 8Ω, f = 1kHz
500
Power Dissipation
vs
Output Power
OCL Headphone Mode
RL = 16Ω, f = 1kHz
750
VDD = 5V
POWER DISSIPATION (mW)
POWER DISSIPATION (mW)
VDD = 5V
400
300
200
VDD = 3.3V
100
600
450
VDD = 3.3V
300
150
POUT = POUTL + POUTR
POUT = POUTL + POUTR
0
0
0
500
1000
1500
2000
2500
0
50
OUTPUT POWER (mW)
400
100
150
300
Figure 28.
Power Dissipation
vs
Output Power
OCL Headphone Mode
RL = 32Ω, f = 1kHz
Power Dissipation
vs
Output Power
CC Headphone Mode
RL = 16Ω, f = 1kHz
250
POWER DISSIPATION (mW)
POWER DISSIPATION (mW)
250
Figure 27.
VDD = 5V
300
200
VDD = 3.3V
100
350
VDD = 5V
200
150
VDD = 3.3V
100
50
POUT = POUTL + POUTR
POUT = POUTL + POUTR
0
0
0
50
100
150
0
200
50
150
100 150
200
250
300 350
OUTPUT POWER (mW)
OUTPUT POWER (mW)
Figure 29.
Figure 30.
Power Dissipation
vs
Output Power
CC Headphone Mode
RL = 32Ω, f = 1kHz
Output Power
vs
Supply Voltage
Speaker Mode
RL = 4Ω, f = 1kHz
3
2.5
125
VDD = 5V
OUTPUT POWER (W)
POWER DISSIPATION (mW)
200
OUTPUT POWER (mW)
100
75
VDD = 3.3V
50
2
THD+N = 10%
1.5
1
THD+N = 1%
0.5
25
POUT = POUTL + POUTR
0
0
0
50
100
150
200
2
2.5
3
3.5
4
4.5
OUTPUT POWER (mW)
SUPPLY VOLTAGE (V)
Figure 31.
Figure 32.
5
5.5
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Typical Performance Characteristics (continued)
Output Power
vs
Supply Voltage
Speaker Mode
RL = 8Ω, f = 1kHz
250
THD+N = 10%
OUTPUT POWER (mW)
OUTPUT POWER (W)
2
Output Power
vs
Supply Voltage
OCL Headphone Mode
RL = 16Ω, f = 1kHz
1.5
1
0.5
200
THD+N = 10%
150
100
50
THD+N = 1%
THD+N = 1%
0
2
150
2.5
3
3.5
4
4.5
5
0
5.5
3.5
4
4.5
Figure 34.
Output Power
vs
Supply Voltage
OCL Headphone Mode
RL = 32Ω, f = 1kHz
Output Power
vs
Supply Voltage
CC Headphone Mode
RL = 16Ω, f = 1kHz
250
OUTPUT POWER (mW)
OUTPUT POWER (mW)
3
Figure 33.
100
THD+N = 10%
75
50
THD+N = 1%
25
2
2.5
SUPPLY VOLTAGE (V)
125
0
2
SUPPLY VOLTAGE (V)
2.5
3
3.5
4
4.5
5
5.5
200
THD+N = 10%
150
100
THD+N = 1%
50
0
5.5
5
2
2.5
3
3.5
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Figure 35.
Figure 36.
Output Power
vs
Supply Voltage
CC Headphone Mode
RL = 32Ω, f = 1kHz
Crosstalk
vs
Frequency
Speaker Mode
VDD = 3.3V, VRIPPLE = 1VP-P, RL = 8Ω
0
150
-10
-20
CROSSTALK (dB)
OUTPUT POWER (mW)
125
100
THD+N = 10%
75
50
THD+N = 1%
-30
-40
-50
-60
-70
-80
25
-90
0
2
2.5
3
3.5
4
4.5
5
5.5
-100
20
100
1k
10k 20k
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
Figure 37.
14
Figure 38.
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Typical Performance Characteristics (continued)
Crosstalk
vs
Frequency
OCL Headphone Mode
VDD = 3.3V, VRIPPLE = 1VP-P, RL = 32Ω
Crosstalk
vs
Frequency
CC Headphone Mode
VDD = 3.3V, VRIPPLE = 1VP-P, RL = 32Ω
-10
-10
-20
-20
-30
-30
0
CROSSTALK (dB)
CROSSTALK (dB)
0
-40
-50
-60
-70
-40
-50
-60
-70
-80
-80
-90
-90
-100
20
-100
20
100
1k
10k 20k
100
1k
10k 20k
FREQUENCY (Hz)
Figure 39.
Figure 40.
Supply Current
vs
Supply Voltage
Speaker Mode, No Load
Supply Current
vs
Supply Voltage
OCL Headphone Mode, No Load
12
6
10
5
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
FREQUENCY (Hz)
8
6
4
2
4
3
2
1
0
2
2.5
3
3.5
4
4.5
5
5.5
0
SUPPLY VOLTAGE (V)
2
2.5
3
3.5
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
Figure 41.
Figure 42.
Supply Current
vs
Supply Voltage
CC Headphone Mode, No Load
Turn-On
Speaker Mode
SUPPLY CURRENT (mA)
6
4
2
0
2
2.5
3
3.5
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
Figure 43.
Figure 44.
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Typical Performance Characteristics (continued)
Turn-Off
Speaker Mode
Turn-On
OCL Headphone Mode
Figure 45.
Figure 46.
Turn-Off
OCL Headphone Mode
Turn-On
CC Headphone Mode
Figure 47.
Figure 48.
Turn-Off
CC Headphone Mode
Figure 49.
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APPLICATION INFORMATION
I2C COMPATIBLE INTERFACE
The LM49270 is controlled through an I2C compatible serial interface that consists of a serial data line (SDA) and
a serial clock (SCL). The clock line is uni-directional. The data line is bi-directional (open-collector), although the
LM49270 does not write to the I2C bus. The LM49270 and the master can communicate at clock rates up to
400kHz. Figure 51 shows the I2C interface timing diagram. The LM49270 is a transmit/receive slave-only device,
reliant upon the master to generate a clock signal.
The master device communicates to the LM49270 by transmitting the proper device address followed by a
command word. Each transmission sequence is framed by a START condition and a STOP condition. Each word
(register address + register content) transmitted over the bus is 8 bits long and is always followed by an
acknowledge pulse.
To avoid an address conflict with another device on the I2C bus, the LM49270 address is determined by the ADR
pin, the state of ADR determines address bit A1 (Table 1). When ADR = 0, the address is 1111 1000. When
ADR = 1 the device address is 1111 1010.
Table 1. 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
Table 2. I2C Control Registers
REG
Register
Name
D7
D6
D5
D4
D3
D2
D1
D0
0
Shutdown
Control
0
0
—
—
HP3DSEL
LS3DSEL
OCL/CC
PWR_ON
1
Headphone
Gain
Control
0
1
—
HP4
HP3
HP2
HP1
HP0
2
Speaker
Gain
Control
1
0
—
LS4
LS3
LS2
LS1
LS0
NOTE
OCL/CC = 1 selects OCL mode; OCL/CC = 0 selects cap coupled mode
PWR_ON = 0 puts part in shutdown
BUS FORMAT
The I2C bus format is shown in Figure 50. 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 is generated. If the LM49270 receives the address correctly, then the LM49270 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 LM49270 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.
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Figure 50. I2C Bus Format
Figure 51. I2C Timing Diagram
GENERAL AMPLIFIER FUNCTION
Class D Amplifier
The LM49270 features a high-efficiency, filterless, Class D stereo amplifier. The LM49270 Class D amplifiers
feature a filterless modulation scheme known as Class BD. The differential outputs of each channel switch at
300kHz from VDD to GND. When there is no input signal applied, the two outputs (LLS+ and LLS-) switch in
phase with a 50% duty cycle. Because the outputs of the LM49270 are differential, there is 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) of each output changes. For increasing output
voltages, the duty cycle of LLS+ increases, while the duty cycle of LLS- decreases. For decreasing output
voltages, the converse occurs. The duty cycle of LLS- increases while the duty cycle of LLS+ decreases. The
difference between the two pulse widths yields the differential output voltage.
Headphone Amplifier
The LM49270 headphone amplifier features two different operating modes, output capacitor-less (OCL) and
capacitor coupled (CC). The OCL architecture eliminates the bulky, expensive output coupling capacitors
required by traditional headphone amplifiers. The LM49270 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 (sleeve) 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. Removing 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 and sound quality. The voltage on
the return sleeve is not an issue when driving headphones. 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 LM49270 detects an output short circuit condition and the
VOC amplifier is disabled preventing damage to the LM49270 and allowing the headphone return to be biased at
GND.
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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 52). In CC mode, the
LM49270 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:
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.
HPL
HPR
VOC
Figure 52. Capacitor Coupled Headphone Mode
Headphone Sense
The LM49270 features a headphone sense input (HPS) that monitors the headphone jack and configures the
device depending on the presence of a headphone. When the HPS pin is low, indicating that a headphone is not
present, the LM49270 speaker amplifiers are active and the headphone amplifiers are disabled. When the HPS
pin is high, indicating that a headphone is present, the headphone amplifiers are active while the speaker
amplifiers are disabled.
POWER DISSIPATION AND EFFICIENCY
The major benefit of Class D amplifier is increased efficiency versus Class AB. The efficiency of the LM49270
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
(RDS(ON)) , along with the switching losses due to gate charge.
The maximum power dissipation per headphone channel in Capacitor Coupled mode is given by:
PDMAX(CC) = VDD2/2π2RL
In OCL mode, the maximum power dissipation increases due to the use of a third amplifier as a buffer. The
power dissipation is given by:
PDMAX(OCL) = VDD2/π2RL
SHUTDOWN FUNCTION
The LM49270 features a shutdown mode 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 LM49270, set
PWR_ON = 0 to disable the device.
AUDIO AMPLIFIER GAIN SETTING
Each channel of the LM49270 features a 32 step volume control. The loudspeaker volume has a range of -47dB
to 30dB and the headphone has a range of -59dB to 18dB (see Table 3).
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Table 3. Volume Control
Volume Step
LS4/HP4
LS3/HP3
LS2/HP2
LS1/HP1
LS0/HP0
LS
Gain (dB)
HP
Gain (dB)
1
0
0
0
0
0
–47
–59
2
0
0
0
0
1
–36
–48
3
0
0
0
1
0
–28.5
–46.5
4
0
0
0
1
1
–22.5
–34.5
5
0
0
1
0
0
–18
–30
6
0
0
1
0
1
–15
–27
7
0
0
1
1
0
–12
–24
8
0
0
1
1
1
–9
–21
9
0
1
0
0
0
–6
–18
10
0
1
0
0
1
–3
–15
11
0
1
0
1
0
–1.5
–13.5
12
0
1
0
1
1
0
–12
13
0
1
1
0
0
1.5
–10.5
14
0
1
1
0
1
3
–9
15
0
1
1
1
0
4.5
–7.5
16
0
1
1
1
1
6
–6
17
1
0
0
0
0
7.5
–4.5
18
1
0
0
0
1
9
–3
19
1
0
0
1
0
10.5
–1.5
20
1
0
0
1
1
12
0
21
1
0
1
0
0
13.5
1.5
22
1
0
1
0
1
15
3
23
1
0
1
1
0
16.5
4.5
24
1
0
1
1
1
18
6
25
1
1
0
0
0
19.5
7.5
26
1
1
0
0
1
21
9
27
1
1
0
1
0
22.5
10.5
28
1
1
0
1
1
24
12
29
1
1
1
0
0
25.5
13.5
30
1
1
1
0
1
27
15
31
1
1
1
1
0
28.5
16.5
32
1
1
1
1
1
30
18
3D ENHANCEMENT
The LM49720 features TI’s 3D sound enhancement. 3D sound improves the apparent stereo channel separation
whenever the left and right speakers are located close to each other, widening the perceived sound stage in
devices with a small form factor that prohibits proper speaker placement.
An external RC network , shown in Figure 1, enables the 3D effect. R3D sets the level of the 3D effect;
decreasing the value of R3D will increase the 3D effect. The 3D network acts like a high pass filter C3D sets the
frequency response; increasing the value of C3D will decrease the low cutoff frequency at which the 3D effect
starts to occur, as shown by this equation:
f3D(-3dB) = 1/2π(R3D)(C3D)
(1)
Enabling the 3D effect increases the gain by a multiplication factor of (1 + 20kΩ/R3D). Setting R3D to 20kΩ
results in a 6dB increase (doubling) of the gain, increasing the 3D effect. The level of 3D effect is also dependent
on other factors such as speaker placement and the distance from the speakers to the listener. The values of
R3D and C3D should be chosen for each application individually, taking into account the physical factors noted
before.
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POWER SUPPLIES
The LM49270 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 LSVDD. The headphone amplifiers, input amplifiers and volume control stages
are powered from HPVDD. 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. HPVDD
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 LM49270 to interface with lower voltage digital controllers.
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
capacitor 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
LM49270 supply pins. A 1µF capacitor is recommended.
Bypass Capacitor Selection
The LM49270 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 LM49270 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:
f(–3dB) = 1/2πRINCIN
(2)
Choose CIN such that f-3dB is well below that lowest frequency of interest. Setting f-3dB too high affects the lowfrequency responses 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 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.
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REVISION TABLE
22
Rev
Date
Description
1.0
12/19/06
Initial release.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM49270SQ/NOPB
ACTIVE
WQFN
RSG
28
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
49270SQ
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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