LM4809
Dual 105mW Headphone Amplifier with Active-Low
Shutdown Mode
General Description
The LM4809 is a dual audio power amplifier capable of
delivering 105mW per channel of continuous average power
into a 16
load with 0.1% (THD+N) from a 5V power supply.
Boomer audio power amplifiers were designed specifically to
provide high quality output power with a minimal amount of
external components. Since the LM4809 does not require
bootstrap capacitors or snubber networks, it is optimally
suited for low-power portable systems.
The unity-gain stable LM4809 can be configured by external
gain-setting resistors.
The LM4809 features an externally controlled, active-low,
micropower consumption shutdown mode, as well as an
internal thermal shutdown protection mechanism.
Key Specifications
n
THD+N at 1kHz at 105mW continuous average power
into 16
0.1% (typ)
n
THD+N at 1kHz at 70mW continuous average power
into 32
0.1% (typ)
n
Shutdown Current
0.4A (typ)
Features
n
Active-low shutdown mode
n
"Click and Pop" reduction circuitry
n
Low shutdown current
n
LLP, MSOP, and SO surface mount packaging
n
No bootstrap capacitors required
n
Unity-gain stable
Applications
n
Headphone Amplifier
n
Personal Computers
n
Microphone Preamplifier
n
PDA's
Typical Application
Boomer
is a registered trademark of National Semiconductor Corporation.
20009001
*Refer to the Application Information Section for information concerning proper selection of the input and output coupling capacitors.
FIGURE 1. Typical Audio Amplifier Application Circuit
November 2002
LM4809
Dual
105mW
Headphone
Amplifier
with
Active-Low
Shutdown
Mode
2002 National Semiconductor Corporation
DS200090
www.national.com
Absolute Maximum Ratings
(Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
6.0V
Storage Temperature
-65C to +150C
ESD Susceptibility (Note 4)
3.5kV
ESD Machine model (Note 8)
250V
Junction Temperature (T
J
)
150C
Soldering Information (Note 1)
Small Outline Package
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
Thermal Resistance
JA
(SO)
170C/W
JC
(SO)
35C/W
JA
(MSOP)
210C/W
JC
(MSOP)
56C/W
JA
(LLP)
117C/W (Note 9)
JA
(LLP)
150C/W (Note 10)
JC
(LLP)
15C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage (V
CC
)
2.0V
V
CC
5.5V
Note 1: See AN-450 "Surface Mounting and their Effects on Product Reli-
ability" for other methods of soldering surface mount devices.
Electrical Characteristics
(Notes 2, 3)
The following specifications apply for V
DD
= 5V unless otherwise specified, limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
LM4809
Units
(Limits)
Typ
(Note 5)
Limit
(Note 7)
V
DD
Supply Voltage
2.0
V (min)
5.5
V (max)
I
DD
Supply Current
V
IN
= 0V, I
O
= 0A
1.4
3
mA (max)
I
SD
Shutdown Current
V
IN
= 0V, V
SHUTDOWN
= GND
0.4
2
A(max)
V
OS
Output Offset Voltage
V
IN
= 0V
4.0
50
mV(max)
P
O
Output Power
THD+N = 0.1%, f = 1kHz
R
L
= 16
105
mW
R
L
= 32
70
65
mW (min)
THD+N
Total Harmonic Distortion
P
O
= 50mW, R
L
= 32
f = 20Hz to 20kHz
0.3
%
Crosstalk
Channel Separation
R
L
= 32
; P
O
= 70mW
70
dB
PSRR
Power Supply Rejection Ratio
C
B
= 1.0F; V
RIPPLE
= 200mV
PP
,
f = 1kHz; Input terminated into 50
70
dB
V
SDIH
Shutdown Voltage Input High
0.8 x V
DD
V (min)
V
SDIL
Shutdown Voltage Input Low
0.2 x V
DD
V (max)
Electrical Characteristics
(Notes 2, 3)
The following specifications apply for V
DD
= 3.3V unless otherwise specified, limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
LM4809
Units
(Limits)
Typ
(Note 5)
Limit
(Note 7)
I
DD
Supply Current
V
IN
= 0V, I
O
= 0A
1.1
mA
I
SD
Shutdown Current
V
IN
= 0V, V
SHUTDOWN
= GND
0.4
A
V
OS
Output Offset Voltage
V
IN
= 0V
4.0
mV
P
O
Output Power
THD+N = 0.1%, f = 1kHz
R
L
= 16
40
mW
R
L
= 32
28
mW
THD+N
Total Harmonic Distortion
P
O
= 25mW, R
L
= 32
f = 20Hz to 20kHz
0.4
%
Crosstalk
Channel Separation
R
L
= 32
; P
O
= 25mW
70
dB
LM4809
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3
Electrical Characteristics
(Notes 2, 3) (Continued)
The following specifications apply for V
DD
= 3.3V unless otherwise specified, limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
LM4809
Units
(Limits)
Typ
(Note 5)
Limit
(Note 7)
PSRR
Power Supply Rejection Ratio
C
B
= 1.0F; V
RIPPLE
= 200mV
PP
,
f = 1kHz; Input terminated into 50
70
dB
V
SDIH
Shutdown Voltage Input High
0.8 x V
DD
V (min)
V
SDIL
Shutdown Voltage Input Low
0.2 x V
DD
V (max)
Electrical Characteristics
(Notes 2, 3)
The following specifications apply for V
DD
= 2.6V unless otherwise specified, limits apply to T
A
= 25C.
Symbol
Parameter
Conditions
LM4809
Units
(Limits)
Typ
(Note 5)
Limit
(Note 7)
I
DD
Supply Current
V
IN
= 0V, I
O
= 0A
0.9
mA
I
SD
Shutdown Current
V
IN
= 0V, V
SHUTDOWN
= GND
0.2
A
V
OS
Output Offset Voltage
V
IN
= 0V
4.0
mV
P
O
Output Power
THD+N = 0.1%, f = 1kHz
R
L
= 16
20
mW
R
L
= 32
16
mW
THD+N
Total Harmonic Distortion
P
O
= 15mW, R
L
= 32
f = 20Hz to 20kHz
0.6
%
Crosstalk
Channel Separation
R
L
= 32
; P
O
= 15mW
70
dB
PSRR
Power Supply Rejection Ratio
C
B
= 1.0F; V
RIPPLE
= 200mV
PP
,
f = 1kHz; Input terminated into 50
70
dB
V
SDIH
Shutdown Voltage Input High
0.8 x V
DD
V (min)
V
SDIL
Shutdown Voltage Input Low
0.2 x V
DD
V (max)
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.
Note 3: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 4: Human body model, 100pF discharged through a 1.5k
resistor.
Note 5: Typical specifications are specified at +25OC and represent the most likely parametric norm.
Note 6: Tested limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 7: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 8: Machine Model ESD test is covered by specification EIAJ IC-121-1981. A 200pF cap is charged to the specified voltage, then discharged directly into the
IC with no external series resistor (resistance of discharge path must be under 50Ohms).
Note 9: The given
JA
is for an LM4809 packaged in an LDA08B wit the Exposed-Dap soldered to a printed circuit board copper pad with an area equivalent to that
of the Exposed-Dap itself.
Note 10: The given
JA
is for an LM4809 packaged in an LDA08B with the Exposed-Dap not soldered to any printed circuit board copper.
External Components Description
(Figure 1)
Components
Functional Description
1. R
i
The inverting input resistance, along with R
f
, set the closed-loop gain. R
i
, along with C
i
, form a high
pass filter with f
c
= 1/(2
R
i
C
i
).
2. C
i
The input coupling capacitor blocks DC voltage at the amplifier's input terminals. C
i
, along with R
i
,
create a highpass filter with f
C
= 1/(2
R
i
C
i
). Refer to the section, Selecting Proper External
Components, for an explanation of determining the value of C
i
.
3. R
f
The feedback resistance, along with R
i
, set closed-loop gain.
4. C
S
This is the supply bypass capacitor. It provides power supply filtering. Refer to the Application
Information section for proper placement and selection of the supply bypass capacitor.
5. C
B
This is the BYPASS pin capacitor. It provides half-supply filtering. Refer to the section, Selecting
Proper External Components, for information concerning proper placement and selection of C
B
.
6. C
O
This is the output coupling capacitor. It blocks the DC voltage at the amplifier's output and forms a high
pass filter with R
L
at f
O
= 1/(2
R
L
C
O
)
LM4809
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