1.0 sec.
鈥?/div>
VDE Approval #0884 (Available with
Option 1, Add -X001 Suf鏗亁)
D E
.021 (0.527)
.035 (0.889)
.130 (3.302)
.150 (3.810)
Pin 1 ID.
.240 (6.096)
.260 (6.604)
.100 (2.540)
1
2
8
4擄
7
6
5
.016 (.406)
.020 (.508 )
.040 (1.016)
.050 (1.270 )
3
4
.050 (1.270)
.010 (0.254) REF.
.280 (7.112)
.330 (8.382)
.380 (9.652)
.400 (10.16)
.300 Typ.
(7.62) Typ.
.020 (0.508) REF.
1
2
3
4
8
.010 (0.254) REF.
V
K1
K2
7
6
5
.008 (0.203)
.012 (0.305)
3擄
9
10擄
.110 (2.794)
.130 (3.302)
APPLICATIONS
鈥?Power Supply Feedback Voltage/Current
鈥?Medical Sensor Isolation
鈥?Audio Signal Interfacing
鈥?Isolate Process Control Transducers
鈥?Digital Telephone Isolation
DESCRIPTION
The IL300 Linear Optocoupler consists of an
AlGaAs IRLED irradiating an isolated feed-
back and an output PIN photodiode in a
bifurcated arrangement. The feedback pho-
todiode captures a percentage of the LED's
鏗倁x and generates a control signal (IP
1
) that
can be used to servo the LED drive current.
This technique compensates for the LED's
non-linear, time, and temperature character-
istics. The output PIN photodiode produces
an output signal (IP
2
) that is linearly related
to the servo optical 鏗倁x created by the LED.
The time and temperature stability of the
input-output coupler gain (K3) is insured by
using matched PIN photodiodes that accu-
rately track the output 鏗倁x of the LED.
A typical application circuit (Figure 1) uses
an operational ampli鏗乪r at the circuit input to
drive the LED. The feedback photodiode
sources current to R1 connected to the
inverting input of U1. The photocurrent, IP1,
will be of a magnitude to satisfy the relation-
ship of (IP1=
V
IN
/R1).
DESCRIPTION
(continued)
The magnitude of this current is directly proportional to the feedback transfer
gain (K1) times the LED drive current (
V
IN
/R1=K1 鈥?/div>
I
F
). The op-amp will supply
LED current to force suf鏗乧ient photocurrent to keep the node voltage (Vb) equal
to Va.
The output photodiode is connected to a non-inverting voltage follower ampli鏗乪r.
The photodiode load resistor, R2, performs the current to voltage conversion. The
output ampli鏗乪r voltage is the product of the output forward gain (K2) times the
LED current and photodiode load, R2 (
V
O
=
I
F
鈥?K2 鈥?R2).
Therefore, the overall transfer gain (V
O
/V
IN
) becomes the ratio of the product of
the output forward gain (K2) times the photodiode load resistor (R2) to the prod-
uct of the feedback transfer gain (K1) times the input resistor (R1). This reduces
to
V
O
/
V
IN
=(K2 鈥?R2)/(K1 鈥?R1). The overall transfer gain is completely indepen-
dent of the LED forward current. The IL300 transfer gain (K3) is expressed as the
ratio of the output gain (K2) to the feedback gain (K1). This shows that the circuit
gain becomes the product of the IL300 transfer gain times the ratio of the output
to input resistors [
V
O
/
V
IN
=K3 (R2/R1)].
Figure 1. Typical application circuit
V
CC
+
Vin
Va
Vb
+
U1
-
I
F
V
CC
1
2
K1
3
4
IL300
K2
8
7
6
5
lp 2
V
CC
V
c
R2
-
U2
+
V
out
V
CC
R1
lp 1
錚?/div>
2001 In鏗乶eon Technologies Corp. 鈥?Optoelectronics Division 鈥?San Jose, CA
www.in鏗乶eon.com/opto 鈥?1-888-In鏗乶eon (1-888-463-4636)
2鈥?28
April 3, 2000-14
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