LM4845 Output Capacitor-less Audio Subsystem with Programmable National 3D
March 2005
LM4845
Output Capacitor-less Audio Subsystem with
Programmable National 3D
General Description
The LM4845 is an audio power amplifier capable of deliver-
ing 500mW of continuous average power into a mono 8Ω
bridged-tied load (BTL) with 1% THD+N, 25mW per channel
of continuous average power into stereo 32Ω single-ended
(SE) loads with 1% THD+N, or an output capacitor-less
(OCL) configuration with identical specification as the SE
configuration, from a 3.3V power supply.
The LM4845 features a 32-step digital volume control and
eight distinct output modes. The digital volume control, 3D
enhancement, and output modes (mono/SE/OCL) are pro-
grammed through a two-wire I
2
C or a three-wire SPI com-
patible interface that allows flexibility in routing and mixing
audio channels. The LM4845 has three input channels: one
pair for a two-channel stereo signal and the third for a
single-channel mono input.
The LM4845 is designed for cellular phone, PDA, and other
portable handheld applications. It delivers high quality output
power from a surface-mount package and requires only
seven external components in the OCL mode (two additional
components in SE mode).
Key Specifications
j
THD+N at 1kHz, 500mW
into 8Ω BTL (3.3V)
j
THD+N at 1kHz, 25mW
1.0% (typ)
1.0% (typ)
2.7 to 5.5V
2.2 to 5.5V
into 32Ω SE (3.3V)
j
Single Supply Operation (V
DD
)
j
I
2
C/SPI Single Supply Operation
Features
n
I
2
C/SPI Control Interface
n
I
2
C/SPI programmable National 3D Audio
n
I
2
C/SPI controlled 32 step digital volume control (-54dB
to +18dB)
n
Three independent volume channels (Left, Right, Mono)
n
Eight distinct output modes
n
microSMD surface mount packaging
n
“Click and Pop” suppression circuitry
n
Thermal shutdown protection
n
Low shutdown current (0.1uA, typ)
Applications
n
Moblie Phones
n
PDAs
Boomer
®
is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation
DS201059
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LM4845
Typical Application
20105966
FIGURE 1. Typical Audio Amplifier Application Circuit-Output Capacitor-less
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2
LM4845
Typical Application
(Continued)
20105967
FIGURE 2. Typical Audio Amplifier Application Circuit-Single Ended
3
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LM4845
Connection Diagrams
25-Bump micro SMD
201059K0
Top View
XY - Date Code
TT - Die Traceability
G - Boomer Family
E5 - LM4845ITL
201059K1
Top View
Bump
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
A1
A2
A3
A4
A5
B1
B2
B3
B4
B5
C1
C2
C3
C4
C5
D1
D2
D3
D4
D5
E1
E2
E3
E4
E5
Name
SDA
I
2
CSPIV
DD
R
HP3D2
R
HP3D1
VOC
Mono-
SCL
ID_ENB
Phone_In
NC
GND
V
DD
V
DD
V
DD
GND
Mono+
NC
L
HP3D1
R
IN
R
OUT
I
2
C SPI_SEL
C
BYPASS
L
HP3D2
L
IN
L
OUT
2
Description
I C or SPI Data
I
2
C or SPI Interface Power Supply
Right Headphone 3D Input 2
Right Headphone 3D Input 1
Center Amplifier Output
Loudspeaker Negative Output
I
2
C or SPI Clock
Address Identification/Enable Bar
Mono Input
No Connect
Ground
Power Supply
Power Supply
Power Supply
GND
Loudspeaker Positive Output
No Connect
Left Headphone 3D Input 1
Right Input Channel
Right Headphone Output
I
2
C or SPI Select
Half-Supply Bypass
Left Headphone 3D Input 2
Left Input Channel
Left Headphone Output
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4
LM4845
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
Storage Temperature
ESD Susceptibility (Note 3)
ESD Machine model (Note 6)
Junction Temperature (T
J
)
Solder Information (Note 1)
6.0V
−65˚C to +150˚C
2.0kV
200V
150˚C
Vapor Phase (60 sec.)
Infrared (15 sec.)
Thermal Resistance
θ
JA
(typ) - TLA25CBA
215˚C
220˚C
65˚C/W (Note 8)
Operating Ratings
(Note 2)
Temperature Range
Supply Voltage (V
DD
)
Supply Voltage (I C/SPI)
2
−40˚C to 85˚C
2.7V
≤
V
DD
≤
5.5V
2.2V
≤
V
DD
≤
5.5V
Electrical Characteristics 3.3V
(Notes 2, 7)
The following specifications apply for V
DD
= 3.3V, T
A
= 25˚C unless otherwise specified. [A
V
= 2 (BTL), A
V
= 1 (SE)]
Symbol
Parameter
Conditions
LM4845
Typical
(Note 4)
Output Modes 2, 4, 6
V
IN
= 0V; No load,
OCL = 0 (Table 2)
Output Modes 1, 3, 5, 7
V
IN
= 0V; No load, BTL,
OCL = 0 (Table 2)
Output mode 0
V
IN
= 0V, Mode 5 (Note 10)
SPKR
OUT
; R
L
= 8Ω
THD+N = 1%; f = 1kHz, BTL, Mode 1
R
OUT
and L
OUT
; R
L
= 32Ω
THD+N = 1%; f = 1kHz, SE, Mode 4
SPKR
OUT
f = 20Hz to 20kHz
P
OUT
= 250mW; R
L
= 8Ω, BTL, Mode 1
R
OUT
and L
OUT
f = 20Hz to 20kHz
P
OUT
= 12mW; R
L
= 32Ω, SE, Mode 4
A-weighted (Note 9), Mode 5, BTL
input referred
V
RIPPLE
= 200mV
PP
; f = 217Hz,
C
B
= 2.2µF, BTL
All audio inputs terminated into 50Ω;
Output referred Gain (BTL) = 6dB
Output Mode 1,7
Output Mode 3
Output Mode 5
PSRR
V
RIPPLE
= 200mV
PP
; f = 217Hz
C
B
= 2.2µF, SE, C
O
= 100µF
All audio inputs terminated into 50Ω;
Output referred Gain,
OCL = 0 (Table 2)
Output Mode 2
Output Mode 4
Output Mode 6, 7
88
88
84
dB
dB
dB
71
68
63
dB
dB
dB
Limits
(Note 5)
Units
(Limits)
3.3
6.5
mA (max)
I
DD
Supply Current
6
0.1
10
500
30
11
1
50
400
20
mA (max)
µA (max)
mV (max)
mW (min)
mW (min)
I
SD
V
OS
Shutdown Current
Output Offset Voltage
P
O
Output Power
0.5
%
THD+N
Total Harmonic Distortion Plus
Noise
0.5
26
%
µV
N
OUT
Output Noise
Power Supply Rejection Ratio
SPKR
OUT
Power Supply Rejection Ratio
R
OUT
and L
OUT
5
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