LM4830
Two-Way Audio Amplification System
with Volume Control
General Description
The LM4830 is an integrated solution for two-way audio am-
plification. It contains a bridge-connected audio power ampli-
fier capable of delivering 1W of continuous average power to
an 8
load with less than 1% THD from a 5V power supply.
It also has the capability of driving 100 mW into a
single-ended 32
impedance for headset operation. There
is a 30 dB attenuator in front of a bridged power amplifier
with 6 dB of gain. The attenuation is controlled through 4 bits
of parallel digital control; 15 steps of 2 dB each.
The device also contains a microphone preamp with two se-
lectable inputs. Mic2 is selected when HS is high and A1 is in
single-ended mode. Mic1 is selected when HS is low and A1
is in bridged mode. This configuration is optimum for switch-
ing between an internal system speaker and external head-
set with microphone. The device also incorporates a buffer
used for driving capacitive loads.
The LM4830 also provides a low-current consumption shut-
down mode making it optimally suited for low-power portable
systems. In addition, the device has an internal thermal shut-
down protection mechanism.
Key Specifications
n
THD at 1W cont. avg P
O
into 8
:
1% (max)
n
Instantaneous peak output power:
1.4W
n
Shutdown current:
0.5 A (typ)
n
Supply voltage range:
2.7V
V
DD
5.5V
Features
n
4-bit digital control for 30 dB of volume attenuation
n
Two selectable microphone inputs
n
High performance microphone preamp
n
Extra buffer for driving long cables
n
No bootstrap capacitors or snubber circuits are
necessary
n
Small Outline (SO) packaging
n
Thermal shutdown protection circuitry
Applications
n
Hands-free phone systems
n
Mobile phone accessories
n
Desktop conference phones
n
Portable computers
n
Teleconference computer applications
Connection Diagram
Dual-In-Line and
Small Outline Packages
DS012677-2
Top View
Order Number LM4830M
See NS Package Number M24B for SO
Order Number LM4830N
See NS Package Number N24A for DIP
January 1999
LM4830
T
wo-W
ay
Audio
Amplification
System
with
V
olume
Control
1999 National Semiconductor Corporation
DS012677
www.national.com
Typical Application
DS012677-1
FIGURE 1. Typical Application Circuit
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2
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
Input Voltage
-0.3V to V
DD
+ 0.3V
Power Dissipation (Note 3)
Internally Limited
ESD Susceptibility (Note 4)
2000V
ESD Susceptibility (Note 5)
250V
Junction Temperature
150C
Soldering Information
Small Outline Package
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
See AN-450
"Surface Mounting and their Effects on
Product Reliability" for other methods of soldering surface
mount devices.
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Supply Voltage
2.7V
V
DD
5.5V
JC
(typ) -- M24B
32C/W
JA
(typ) -- M24B
79C/W
JC
(typ) -- N24A
21C/W
JA
(typ) -- N24A
61C/W
Electrical Characteristics
(Notes 1, 2)
The following specifications apply for V
DD
= 5V, unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4830
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
POWER AMPLIFIER, A1
I
DD
Quiescent Power Supply Current
V
O
= 0V, I
O
= 0A, R
L
=
5.8
mA (min)
11.0
20.0
mA (max)
Bridged R
L
= 8
11.4
mA
HS = 5V, SD = 0V, V
O1
On Only
7.9
mA
I
SD
Shutdown Current
HS = 5V, SD = 5V, IC Off
0.5
2.0
A (max)
V
OS
Output Offset Voltage
V
IN
= 0V
0.7
50.0
mV (max)
e
IN
Input Noise
IHF-A Weighting Filter, R
S
= 25
Bridged Output, V
O1
V
O2
, R
L
= 8
30
V
Single-Ended Output, V
O1
, R
L
= 32
16
V
P
O
Output Power, Bridged
THD = 1% (max); f = 1 kHz, R
L
= 8
1.15
1.0
W (min)
THD+N = 10%; f = 1 kHz, R
L
= 8
1.4
W
THD+N = 10%; f = 1 kHz, R
L
= 4
2
W
THD
Total Harmonic Distortion
f = 1 kHz, Attenuation
@
0 dB
P
O
= 1.5W, R
L
= 4
0.2
%
P
O
= 1W, R
L
= 8
0.2
%
V
O1
On Only, V
O
= 60 mV, R
L
= 32
0.06
%
Attenuation Step Size Error
0 dB to -30 dB
0.5
dB
Absolute Attenuation
Attenuation
@
0 dB
0.5
dB
Attenuation
@
-30 dB
1.0
dB
R
IN
Power Amp Input Resistance
40
k
DIGITAL INPUTS
V
IH
High Input Voltage
CMOS Compatible Only
4.5
V
V
IL
Low Input Voltage
CMOS Compatible Only
0.5
V
PREAMP, A2
R
IN
Mic1 and Mic2 Input Resistance
21.5
k
V
OS
Output Offset Voltage
V
IN
= 0V
2.0
mV
e
IN
Input Noise
IHF-A Weighting Filter, R
S
= 25
1.3
10.0
V (max)
THD
Total Harmonic Distortion
A
VCL
= 100, V
IN
= 10 mVrms, f = 1 kHz
0.06
%
A
VCL
= -1, P
O
= 50 mW, f = 1 kHz, R
L
=
32
0.02
(Refer to
Figure 2 )
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3
Electrical Characteristics
(Notes 1, 2) (Continued)
The following specifications apply for V
DD
= 5V, unless otherwise specified. Limits apply for T
A
= 25C.
Symbol
Parameter
Conditions
LM4830
Units
(Limits)
Typical
Limit
(Note 6)
(Note 7)
PREAMP, A2
Xtalk
Crosstalk
A
VCL
= 100, Power Amp: P
O
= 1W,
R
L
= 8
, f = 1 kHz
-72
dB
PSRR
Power Supply Rejection Ratio
V
DDAC
= 0.5 V
PP
, f = 1 kHz
60
dB
MICROPHONE BUFFER, A3
R
IN
Buffer Input Resistance
17
k
V
OS
Output Offset Voltage
V
IN
= 0V
2.0
mV
e
IN
Input Noise
IHF-A Weighting Filter, R
S
= 25
5.8
V
THD
Total Harmonic Distortion
P
O
= 50 mW, f = 1 kHz, R
L
= 32
0.5
%
Xtalk
Crosstalk
Power Amp: P
O
= 1W, R
L
= 8
, f = 1 kHz
-76
dB
Note 1: All voltages are measured with respect to the ground pins (Pins 2, 15, and 24), unless otherwise specified.
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is func-
tional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guar-
antee 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 T
JMAX
,
JA
, and the ambient temperature, T
A
. The maximum
allowable power dissipation is P
DMAX
= (T
JMAX
- T
A
)/
JA
or the number given in the Absolute Maximum Ratings, whichever is lower. For the LM4830M, T
JMAX
=
+150C, and the typical junction-to-ambient thermal resistance, when board mounted, is 79C/W.
Note 4: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 5: Machine model, 200 pF240 pF discharged through all pins.
Note 6: Typicals are measured at 25C and represent the parametric norm.
Note 7: Limits are guarantees that all parts are tested in production to meet the stated values.
Timing Diagram
DS012677-3
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4
Computer Application Circuit
DS012677-4
FIGURE 2.
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