IL300
LINEAR OPTOCOUPLER
FEATURES
• Couples AC and DC signals
• 0.01% Servo Linearity
• Wide Bandwidth, >200 KHz
• High Gain Stability,
±
0.005%/C
• Low Input-Output Capacitance
• Low Power Consumption, < 15mw
• Isolation Test Voltage, 5300 VAC
RMS
,
1 sec.
• Internal Insulation Distance, >0.4
mm
for VDE
• Underwriters Lab File #E52744
• VDE Approval #0884 (Optional with
Option 1, Add -X001 Suffix)
• IL300G Replaced by IL300-X006
APPLICATIONS
• Power Supply Feedback Voltage/
Current
• Medical Sensor Isolation
• Audio Signal Interfacing
• Isolate Process Control Transducers
• Digital Telephone Isolation
DESCRIPTION
The IL300 Linear Optocoupler consists of
an AlGaAs IRLED irradiating an isolated
feedback and an output PIN photodiode
in a bifurcated arrangement. The feed-
back photodiode captures a percentage
of the LED's flux and generates a control
signal (IP
1
) that can be used to servo the
LED drive current. This technique com-
pensates for the LED's non-linear, time,
and temperature characteristics. The out-
put PIN photodiode produces an output
signal (IP
2
) that is linearly related to the
servo optical flux created by the LED.
The time and temperature stability of the
input-output coupler gain (K3) is insured
by using matched PIN photodiodes that
accurately track the output flux of the
LED.
A typical application circuit (Figure 1)
uses an operational amplifier at the circuit
input to drive the LED. The feedback
photodiode sources current to R1 con-
nected to the inverting input of U1. The
photocurrent, IP1, will be of a magnitude
to satisfy the relationship of (IP1=V
IN
/R1).
Dimensions in inches (mm)
4
3
2
1
Pin One I.D.
1
8
.268 (6.81)
.255 (6.48)
5
6
7
8
2
3
4
.390 (9.91)
.379 (9.63)
.045 (1.14) .150 (3.81)
.030 (.76) .130 (3.30)
K1
K2
7
6
5
.305 Typ.
(7.75) Typ.
.135 (3.43)
.115 (2.92)
4° Typ.
.022 (.56)
.018 (.46)
.040 (1.02)
.030 (.76 )
.100 (2.54) Typ.
10° Typ.
3°–9°
.012 (.30)
.008 (.20)
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 • I
F
). The op-amp will supply LED cur-
rent to force sufficient photocurrent to keep the node voltage (Vb) equal to Va
The output photodiode is connected to a non-inverting voltage follower amplifier. The
photodiode load resistor, R2, performs the current to voltage conversion. The output
amplifier voltage is the product of the output forward gain (K2) times the LED current
and photodiode load, R2 (V
O
=I
F
• K2 • 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 product of the
feedback transfer gain (K1) times the input resistor (R1). This reduces to V
O
/V
IN
=
(K2 • R2)/(K1 • R1). The overall transfer gain is completely independent of the LED
forward current. The IL300 transfer gain (K3) is expressed as the ratio of the ouput
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
Va
+
Vin
Vb
1
+
U1
V
CC
2
IF
V
CC
K1
3
4
lp 1
IL300
8
7
6
5
lp 2
V
CC
Vc
R2
K2
-
-
U2
+
V
CC
Vout
R1
5–1
IL300 Terms
KI—Servo Gain
The ratio of the input photodiode current (I
P1
) to the LED cur-
rent(I
F
). i.e., K1 = I
P1
/ I
F
.
K2—Forward Gain
The ratio of the output photodiode current ( I
P2
) to the LED
current (I
F
), i.e., K2 = I
P2
/ I
F
.
K3—Transfer Gain
The Transfer Gain is the ratio of the Forward Gain to the Servo
gain, i.e., K3 = K2/K1.
∆
K3—Transfer Gain Linearity
The percent deviation of the Transfer Gain, as a function of
LED or temperature from a specific Transfer Gain at a fixed
LED current and temperature.
Photodiode
A silicon diode operating as a current source. The output cur-
rent is proportional to the incident optical flux supplied by the
LED emitter. The diode is operated in the photovoltaic or pho-
toconductive mode. In the photovoltaic mode the diode func-
tions as a current source in parallel with a forward biased
silicon diode.
The magnitude of the output current and voltage is depen-
dant upon the load resistor and the incident LED optical flux.
When operated in the photoconductive mode the diode is
connected to a bias supply which reverse biases the silicon
diode. The magnitude of the output current is directly propor-
tional to the LED incident optical flux.
LED (Light Emitting Diode)
An infrared emitter constructed of AlGaAs that emits at 890
nm operates efficiently with drive current from 500
µ
A to 40
mA. Best linearity can be obtained at drive currents between
5 mA to 20 mA. Its output flux typically changes by –0.5%/
°
C
over the above operational current range.
Absolute Maximum Ratings
Symbol
Emitter
Power Dissipation
(T
A
=25
°
C)
Derate Linearly from 25
°
C
Forward Current
Surge Current
(Pulse width <10
µ
s)
Reverse Voltage
Thermal Resistance
Junction Temperature
Detector
Power Dissipation
Derate linearly from 25
°
C
0.65
Reverse Voltage
Junction Temperature
Thermal Resistance
Coupler
Total Package
Dissipation at 25
°
C
Derate linearly from 25
°
C
Storage Temperature
Operating Temperature
Isolation Test Voltage
Isolation Resistance
V
IO
=500 V, T
A
=25
°
C
V
IO
=500 V, T
A
=100
°
C
T
S
T
OP
–55
–55
5300
10
12
10
11
P
T
210
2.8
150
100
mW
mW/
°
C
°
C
°
C
VAC
RMS
Ω
Ω
V
R
T
J
Rth
50
100
1500
P
DET
50
mA
mW/
°
C
V
°
C
°
C/W
lf
lpk
V
R
Rth
T
J
P
LED
160
2.13
60
250
5
470
100
mW
mW/
°
C
mA
mA
V
°
C/W
°
C
Min.
Max.
Unit
IL300
5–2
Characteristics
(T
A
=25
°
C)
Symbol
LED Emitter
Forward Voltage
V
F
Temperature Coefficient
Reverse Current
Junction Capacitance
Dynamic Resistance
Switching Time
Detector
Dark Current
Open Circuit Voltage
Short Circuit Current
Junction Capacitance
Noise Equivalent Power
Coupled Characteristics
K1, Servo Gain (I
P1
/I
F
)
Servo Current, see Note 1, 2
K2, Forward Gain (I
P2
/I
F
)
Forward Current
K3, Transfer Gain (K2/K1)
See Note 1, 2
Transfer Gain Linearity
Transfer Gain Linearity
Photoconductive Operation
Frequency Response
Phase Response at 200 KHz
Rise Time
Fall Time
Package
Input-Output Capacitance
Common Mode Capacitance
Common Mode Rejection Ratio
Notes
1. Bin Sorting:
K3 (transfer gain) is sorted into bins that are
±5%,
as follows:
Bin A=0.557–0.626
Bin B=0.620–0.696
Bin C=0.690–0.773
Bin D=0.765–0.859
Bin E=0.851–0.955
Bin F=0.945–1.061
Bin G=1.051–1.181
Bin H=1.169–1.311
Bin I=1.297–1.456
Bin J=1.442–1.618
K3=K2/K1. K3 is tested at I
F
=10 mA, V
det
=–15 V.
C
IO
C
cm
CMRR
1
0.5
130
pF
pF
dB
V
F
=0 V, f=1 MHz
V
F
=0 V, f=1 MHz
f=60 Hz, R
L
=2.2 KΩ
t
R
t
F
BW (-3 db)
200
-45
1.75
1.75
KHz
Deg.
µs
µs
I
Fq
=10 mA, MOD=±4 mA, R
L
=50
Ω,
V
det
=-15 V
K1
I
P
1
K2
I
P
2
K3
∆K3
∆K3
0.56
0.0036
0.0050
0.007
70
0.007
70
1.00
±0.25
±0.5
1.65
0.011
µA
K2/K1
%
%
0.011
µ
A
I
F
=10 mA, V
det
=-15 V
I
F
=10 mA, V
det
=-15 V
I
F
=10 mA, V
det
=-15 V
I
F
=10 mA, V
det
=-15 V
I
F
=10 mA, V
det
=-15 V
I
F
=1 to 10 mA
I
F
=1 to 10 mA, T
A
=0
°
C to 75
°
C
I
D
V
D
I
SC
C
J
NEP
1
500
70
12
4 x 10
14
25
nA
mV
µ
A
pF
W/
√
Hz
V
det
=-15 V, I
F
=0
µ
A
I
F
=10 mA
I
F
=10 mA
V
F
=0 V, f=1 MHz
V
det
=15 V
V
F
∆
V
F
/
∆°
C
I
R
C
J
∆
V
F
/
∆
I
F
t
R
t
F
1.25
-2.2
1
15
6
1
1
10
1.50
V
mV/
°
C
µ
A
pF
Ω
µ
s
µ
s
V
R
=5 V
V
F
=0 V, f=1 MHz
I
F
=10 mA
∆
I
F
=2 mA, I
Fq
=10 mA
∆
I
F
=2 mA, I
Fq
=10 mA
I
F
=10 mA
Min.
Typ.
Max.
Unit
Test Condition
2. Bin Categories: All IL300s are sorted into a K3 bin, indicated by an
alpha character that is marked on the part. The bins range from “A”
through “J”.
The IL300 is shipped in tubes of 50 each. Each tube contains only
one category of K3. The category of the parts in the tube is marked
on the tube label as well as on each individual part.
3. Category Options: Standard IL300 orders will be shipped from the
categories that are available at the time of the order. Any of the ten
categories may be shipped. For customers requiring a narrower
selection of bins, four different bin option parts are offered.
IL300-DEFG: Order this part number to receive categories D,E,F,G
only.
IL300-EF: Order this part number to receive categories E, F only.
IL300-E: Order this part number to receive category E only.
IL300-F: Order this part number to receive category F only
IL300
5–3
Figure 2. LED forward current vs. forward voltage
35
Figure 6. Normalized servo photocurrent vs. LED
current and temperature
3.0
Normalized Photocurrent
IF - LED Current - mA
30
25
20
15
10
5
0
1.0
2.5
2.0
1.5
1.0
0.5
0.0
Normalized to:IP1 @ I
F
=10 mA,
T
A
=25°C,
0°C
V =–15 V
D
25°C
50°C
75°C
1.1
1.2
1.3
1.4
0
5
10
15
20
25
VF - LED Forward Voltage - V
IF - LED Current - mA
Figure 3. LED forward current vs. forward voltage
100
Figure 7. Normalized servo photocurrent vs. LED
current and temperature
10
IP1- Normalized Photocurrent
Normalized to IP1 @ I
F
=10 mA,
T
A
=25°C,
V
D
=–15 V
0°C
25°C
50°C
75°C
IF - LED Current - mA
10
1
1
.1
.1
1.0
1.1
1.2
1.3
VF - LED Forward Voltage - V
1.4
.01
.1
1
10
100
IF - LED Current - mA
Figure 4. Servo photocurrent vs. LED current and
temperature
300
Figure 8. Servo gain vs. LED current and temperature
1.2
1.0
0.8
0.6
0.4
0.2
0.0
.1
NK1- Normalized Servo Gain
IP1- Servo Photocurrent -
µA
250
200
150
100
50
0
.1
0°C
25°C
50°C
75°C
V
D
=–15 V
0°
25°
50°
75°
85°
1
10
100
1
10
100
IF - LED Current - mA
IF - LED Current - mA
Figure 5. Servo photocurrent vs. LED current
and temperatureFigure
temperature
LED current and
1000
0°C
25°C
50°C
75°C
Figure 9. Normalized servo gain vs. LED current
and temperature
1.2
0°
25°
50°
75°
100°
0.6
0.4
0.2
0.0
NK1- Normalized Servo Gain
V
D
=–15
-15V
Vd =
V
1.0
0.8
IP1- Servo Photocureent -
µA
100
10
Normalized to:
I
F
=10 mA, T
A
=25°C
.1
1
10
IF - LED Current - mA
100
1
.1
1
10
IF - LED Current - mA
100
IL300
5–4
Figure 10. Transfer gain vs. LED current and temperature
1.010
Figure 14. Common mode rejection
-60
CMRR - Rejection Ratio - dB
K3 - Transfer Gain - (K2/K1)
0°C
1.005
25°C
1.000
-70
-80
-90
-100
-110
-120
-130
10
50°C
75°C
0.995
0.990
0
5
10
15
20
25
100
1000
10000
100000
1000000
IF - LED Current - mA
F - Frequency - Hz
Figure 11. Normalized transfer gain vs. LED current
and temperature
1.010
0°C
1.005
25°C
1.000
50°C
75°C
0.995
Figure 15. Photodiode junction capacitance vs. reverse
voltage
14
K3 - Transfer Gain - (K2/K1)
Normalized to I
F
=10 mA, T
A
=25°C
Capacitance - pF
12
10
8
6
4
2
0
0.990
0
5
10
15
20
25
IF - LED Current - mA
0
2
4
6
8
10
Voltage - V
det
Application Considerations
Figure 12. Amplitude response vs. frequency
5
I
F
=10 mA, Mod=± 2 mA (peak)
Amplitude Response - dB
0
R
L
=1 KΩ
-5
-10
In applications such as monitoring the output voltage from a
line powered switch mode power supply, measuring bioelectric
signals, interfacing to industrial transducers, or making floating
current measurements, a galvanically isolated, DC coupled
interface is often essential. The IL300 can be used to construct
an amplifier that will meet these needs.
The IL300 eliminates the problems of gain nonlinearity and drift
induced by time and temperature, by monitoring LED output
flux.
A PIN photodiode on the input side is optically coupled to the
LED and produces a current directly proportional to flux falling
on it . This photocurrent, when coupled to an amplifier, provides
the servo signal that controls the LED drive current.
The LED flux is also coupled to an output PIN photodiode. The
output photodiode current can be directly or amplified to sat-
isfy the needs of succeeding circuits.
Isolated Feedback Amplifier
The IL300 was designed to be the central element of DC cou-
pled isolation amplifiers. Designing the IL300 into an amplifier
that provides a feedback control signal for a line powered
switch mode power is quite simple, as the following example
will illustrate.
See Figure 17 for the basic structure of the switch mode supply
using the Siemens TDA4918 Push-Pull Switched Power Supply
Control Chip. Line isolation and insulation is provided by the
high frequency transformer. The voltage monitor isolation will
be provided by the IL300.
R
L
=10 KΩ
-15
-20
10 4
10 5
F - Frequency - Hz
10 6
Figure 13. Amplitude and phase response vs. frequency
5
45
dB
PHASE
Amplitude Response - dB
0
0
-5
-45
-10
-90
-15
I
Fq
=10 mA
Mod=± 4 mA
T
A
=25°C
RL=50
Ω
10 4
10 5
10 6
F - Frequency - Hz
-135
-20
10 3
-180
10 7
Ø - Phase Response -°
IL300
5–5
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