TECHNICAL DATA
IL34119
Low Power Audio Amplifier
The IL34119 is a low power audio amplifier integrated circuit
intended (primarily) for telephone applications, such as in
speakerphones. It provides differential speaker outputs to maximize
output swing at low supply voltages (2.0 volts minimum). Coupling
capacitors to the speaker are not required. Open loop gain is 80 dB,
and the closed loop gain is set with two external resistors. A Chip
Disable pin permits powering down and/or muting the input signal.
The IL34119 is available in a standard 8 pin DIP or a surface mount
package.
•
Wide Operating Supply Voltage Range (2-16 Volts) - Allows
Telephone Line Powered Applications
•
Low Quiescent Supply Current for Battery Powered Applications
•
Chip Disable Input to Power Down the IC
•
Low Power Down Quiescent Current
•
Drives a Wide Range of Speaker Loads (8-100Ω)
•
Output Power Exceeds 250 mW with 32Ω Speaker
•
Low Total Harmonic Distortion
•
Gain Adjustable from <0 dB to >46 dB for Voice Band
•
Requires Few External Components
ORDERING INFORMATION
IL34119N Plastic
IL34119D SOIC
T
A
= -10° to 70° C for
all packages
PIN ASSIGNMENT
SIMPLIFIED BLOCK DIAGRAM
* = Optional
R
Differential Gain = 2 x
f
R
i
1
IL34119
PIN DESCRIPTION
Pin
1
2
3
Symbol
CD
FC2
FC1
Description
Chip Disable - Digital input. A Logic “0” (<0.8 V) sets normal operation. A Logic “1”
(≥2.0 V) sets the power down mode. Input impedance is nominally 90 KΩ.
A capacitor at this pin increases power supply rejection, and affects turn-on time. This
pin can be left open if the capacitor at FC1 is sufficient.
Analog Ground for the amplifiers. A 1.0
µF
capacitor at this pin (with a 5.0
µF
capacitor at Pin 2) provides 52 dB of power supply rejection. Turn-on time of the
circuit is affected by the capacitor on this pin. This pin can be used as an alternate
input.
Amplifier input. The input capacitor and resistor set low frequency rolloff and input
impedance. The feedback resistor is connected to this pin and VO1.
Amplifier Output #1. The dc level is
≈
(V
CC
- 0.7 V)/2.
DC supply voltage (+2.0 to +16 Volts) is applied to this pin.
Ground pin for the entire circuit.
Amplifier Output #2. This signal is equal in amplitude, but 180° out of phase with that
at VO1. The dc level is
≈
(V
CC
- 0.7 V)/2.
4
5
6
7
8
V
IN
VO1
V
CC
GND
VO2
DESIGN GUIDELINES
GENERAL
The IL34119 is a low power audio amplifier
capable of low voltage operation (V
CC
= 2.0 V
minimum) such as that encountered in line-powered
speakerphones. The circuit provides a differential
output (VO1-VO2) to the speaker to maximize the
available voltage swing at low voltages. The
differential gain is set by two external resistors. Pins
FC1 and FC2 allow controlling the amount of power
supply and noise rejection, as well as providing
alternate inputs to the amplifiers. The CD pin permits
powering down the IC for muting purposes and to
conserve power.
sourcing and sinking a peak current of 200 mA. The
outputs can typically swing to within
≈0.4
volts above
ground, and to within
≈1.3
volts below V
CC
, at the
maximum current. The output dc offset voltage
(VO1-VO2) is primarily a function of the feedback
resistor (R
f
), and secondarily due to the amplifiers’
input offset voltages. The input offset voltage of the
two amplifiers will generally be similar for a
particular IC, and therefore nearly cancel each other
at the outputs. Amplifier #1’s bias current, however,
flows out of V
IN
(Pin 4) and through R
f
, forcing VO1
to shift negative by an amount equal to [R
f
x I
IB
].
VO2 is shifted positive an equal amount. The output
offset voltage specified in the Electrical
Characteristics is measured with the feedback resistor
shown in the Simplified Block Diagram, and
therefore takes into account the bias current as well as
internal offset voltages of the amplifiers. The bias
current is constant with respect to V
CC
.
AMPLIFIERS
Referring to the block diagram, the internal
configuration consists of two identical operational
amplifiers. Amplifier #1 has an open-loop gain of
≥80
dB (at f
≤
100 Hz), and the closed loop gain is
set by external resistors R
f
and R
i
. The amplifier is
unity gain stable, and has a unity gain frequency of
approximately 1.5 MHz. In order to adequately cover
the telephone voice band (300-340 Hz), a maximum
closed loop gain of 46 dB is recommended. Amplifier
#2 is internally set to a gain of -1.0 (0 dB).
The outputs of both amplifiers are capable of
FC1 and FC2
Power supply rejection is provided by the
capacitors (C1 and C2 in the Simplified Block
Diagram) at FC1 and FC2. C2 is somewhat dominant
at low frequencies, while C1 is dominant at high
frequencies. The reguired values of C1 and C2
depend on the conditions of each application. A
2
IL34119
line powered speakerphone, for example, will require
more filtering than a circuit powered by a well
requlated power supply. The amount of rejection is a
function of the capacitors, and the equivalent
impedance looking into FC1 and FC2 (listed in the
Electrical Characteristics as R
FC1
and R
FC2
).
In addition to providing filtering, C1 and C2 also
affect the turn-on time of the circuit at power-up,
since the two capacitors must change up through the
internal 50 KΩ and 125 KΩ resistors.
and load power.The maximum power which can
safely be dissipated within the IL34119 is found from
the following equation:
P
D
= (140°C - T
A
)/θ
JA
where T
A
is the operating temperature;
and
θ
JA
is the package thermal resistance (100°C/W
for the standard DIP package, and 180°C/W for the
surface mount package).
The power dissipated within the IL34119, in a
given application, is found from the following
eguation:
P
D
= (V
CC
x I
CC
) + (I
RMS
x V
CC
) - (R
L
x I
RMS2
).
where I
CC
is obtained from Figure 1;
and I
RMS
is the RMS current at the load;
and R
L
is the load resistance.
Figures 2-4, along with Figures 5-7 (distortion
curves), and a peak working load current of
±200
mA, define the operating range for the
IL34119. The operating range is further defined in
terms of allowable load power in Figure 8 for load of
8.0
Ω,
16
Ω,
and 32
Ω.
The left (ascending) portion
of each of the three curves is defined by the power
level at which 10% distortion occurs. The center flat
portion of each curve is defined by the maximum
output current capability of the IL34119. The right
(descending) portion of each curve is defined by the
maximum internal power dissipation of the IC at
25°C. At higher operating be reduced according to
the above equations. Operating the device beyond the
current and junction temperature limits will degrade
long term reliability.
CHIP DISABLE
The Chip Disable (Pin 1) can be used to power
down the IC to conserve power, or for muting, or
both. When at a Logic “0” (0 to 0.8 Volts), the
IL34119 is enabled for normal operation. When Pin 1
is at a Logic “1” (2.0 to V
CC
Volts), the IC is
disabled. If Pin 1 is open, that is equivalent to a Logic
“0”, although good design practice dictates that an
input should never be left open. Input impedance at
Pin 1 is a nominal 90 KΩ. The power supply current
(when disabled) is shown in Figure 1.
Muting, defined as the change in differential gain
from normal operation to muted operation, is in
excess of 70 dB. The turn-off time of the audio
output, from the application of the CD signal, is
<2.0
µs,
and turn on-time is 12-15 ms. Both times are
independent of C1, C2, and V
CC
.
When the IL34119 is disabled, the voltages at
FC1 and FC2 do not change as they are powered
from V
CC
. The outputs, VO1 and VO2, change to a
high impedance condition, removing the signal from
the speaker. If signals from other sources are to be
applied to the outputs (while disabled), they must be
within the range of V
CC
and Ground.
LAYOUT CONSIDERATIONS
Normally a snubber is not needed at the output of
the IL34119, unlike many other audio amplifiers.
However, the PC board layout, stray capacitances,
and the manner in which the speaker wires are
configured, may dictate otherwise. Generally the
speaker wires should be twisted tightly, and be not
more than a few inches in length.
POWER DISSIPATION
Figures 2-4 indicate the device dissipation (within
the IC) for various combinations of V
CC
, R
L
,
MAXIMUM RATINGS
*
Symbol
V
CC
I
OUT
V
IN
V
VO
Tstg
*
Parameter
Supply Voltage
Maximum Output Current at VO1, VO2
MaximumInput Voltage(FC1, FC2, CD, V
IN
)
Applied Output Voltage to VO1, VO2 when disabled
Storage Temperature Range
Value
1.0 to +18
±250
-1.0 toV
CC
+1.0
-1.0 toV
CC
+1.0
-65 to +150
Unit
V
mA
V
V
°C
Maximum Ratings are those values beyond which damage to the device may occur.
Functional operation should be restricted to the Recommended Operating Conditions.
3
IL34119
RECOMMENDED OPERATING CONDITIONS
Symbol
V
CC
R
L
I
L
AVD
VCD
T
A
Supply Voltage
Load Impedance
Peak Load Current
Differential Gain (5.0 KHz bandwidth)
Voltage @ CD (Pin 1)
Operating Temperature, All Pakage Types
Parameter
Min
2.0
8.0
-
0
0
-10
Max
16
100
200
46
V
CC
+70
Unit
V
Ω
mA
dB
V
°C
This device contains protection circuitry to guard against damage due to high static voltages or electric
fields. However, precautions must be taken to avoid applications of any voltage higher than maximum rated
voltages to this high-impedance circuit. For proper operation, V
IN
and V
OUT
should be constrained to the range
GND≤(V
IN
or V
OUT
)≤V
CC
.
Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or V
CC
).
Unused outputs must be left open.
ELECTRICAL CHARACTERISTICS
(T
A
= -10 to +70°C, V
CD
= 0 V)
Symbol
Parameter
Test Conditions
Guaranteed
Limits
Min
AMPLIFIERS (DC CHARACTERISTICS)
V
O
V
OH
V
OL
∆V
O
I
IB
R
FC1
R
FC2
V
IH
V
IL
R
CD
Output DC Level (VO1, VO2)
Output High Level
Output Low Level
Output DC Offset Voltage
(VO1-VO2)
Input Bias Current @ VIN
Equivalent Resistance @ FC1
Equivalent Resistance @ FC2
Minimum High-Level Input
Voltage
Maximum Low-Level Input
Voltage
Input Resistance
V
CC
= V
CD
= 16 V
V
CC
=3.0 V, R
L
=16Ω
R
f
= 75 KΩ
I
OUT
= -75 mA, V
CC
= 2.0 V
I
OUT
= 75 mA,
2.0 V
≤
V
CC
≤
16 V
V
CC
=6.0 V, R
L
=32Ω
R
f
= 75 kΩ
V
CC
=6.0 V
V
CC
= 6.0 V
V
CC
= 6.0 V
0.75
0.5
-
-200
-
100
18
2.0
-
50*
1.75
-
0.55
200
1600
220
40
-
0.8
175*
V
V
V
mV
nA
KΩ
KΩ
V
V
KΩ
(continued)
Max
Unit
4
IL34119
ELECTRICAL CHARACTERISTICS
(T
A
= -10 to +70°C, V
CD
= 0 V)
Symbol
Parameter
Test Conditions
Guaranteed
Limits
Min
AMPLIFIERS (AC CHARACTERISTICS)
r
i
A
VOL1
A
V2
GBW
P
OUT3
P
OUT12
THD
PSRR
GMT
Total Harmonic Distortion
Power Supply Rejection
Muting
AC Input Resistance (V
IN
)
Open Loop Gain (Amplifier
#1)
Closed Loop Gain (Amplifier
#2)
Gain Bandwidth Product
Output Power
V
CC
= 3.0 V, R
L
= 16
Ω,
THD
≤
10%, V
FC2
= 1.15 V
V
CC
= 12.0 V, R
L
= 100
Ω,
THD
≤
10%, V
FC2
=12 V
V
CC
= 6.0 V, R
L
= 32
Ω,
f = 1.0 KHz, P
OUT
= 125 mW
V
CC
= 6.0 V,
∆V
CC
= 3.0 V,
C1 =∞, C2 = 0.01
µF
V
CC
= 6.0 V, f = 1.0 kHz,
CD = 2.0 V
V
CC
=3.0 V, R
L
=∞,CD=0.8V
V
CC
=3.0 V, R
L
=∞,CD=2.0V
f = 100 Hz, V
CC
= 6.0 V,
V
FC2
= 2.65 V
f = 1.0 KHz, V
CC
= 6.0 V,
R
L
=32
Ω
22.5
60
-0.35
1.125
55
400*
-
35
50
-
-
+0.35
-
-
-
5.0
-
-
%
dB
dB
MΩ
dB
dB
MHz
mW
Max
Unit
POWER SUPPLY
I
CC1
I
CC2
*
Maximum Power Supply
Current
@25°C
-
-
5.0
125
mA
µA
Figure 1. POWER SUPPLY CURRENT
Figure 2. DEVICE DISSIPATION
8.0
Ω
LOAD
5
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