IL300-DEFG Infineon Technologies, IL300-DEFG Datasheet - Page 9

• Manufacturer Part Number: IL300-DEFG
• Description: Optoisolator; Analog; 8-Pin DIP; Photodiode; w/Feedback Photodiode
• Manufacturer: Infineon Technologies
• Type: Analogr

Specifications of IL300-DEFG

• Input Type: LED
• Output Type: Photodiode
• Package Type: 8-Pin DIP
• Special Features: Feedback Photodiode
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

The isolated amplifier provides the PWM control sig-
nal which is derived from the output supply voltage.
Figure 16 more closely shows the basic function of
the amplifier.
The control amplifier consists of a voltage divider and
a non-inverting unity gain stage. The TDA4918 data
sheet indicates that an input to the control amplifier is
a high quality operational amplifier that typically
requires a +3.0 V signal. Given this information, the
amplifier circuit topology shown in Figure 18 is
selected.
The power supply voltage is scaled by R1 and R2 so
that there is + 3.0 V at the non-inverting input (Va) of
U1. This voltage is offset by the voltage developed by
photocurrent flowing through R3. This photocurrent is
developed by the optical flux
created by current flowing through the LED. Thus as
the scaled monitor voltage (Va) varies it will cause a
change in the LED current necessary to satisfy the dif-
ferential voltage needed across R3 at the inverting
input.
The first step in the design procedure is to select the
value of R3 given the LED quiescent current (IFq) and
the servo gain (K1). For this design, I
ure 4 shows the servo photocurrent at I
be 100 µA. With this data R3 can be calculated.
For best input offset compensation at U1, R2 will
equal R3. The value of R1 can easily be calculated
from the following.
Document Number 83622
Rev. 1.5, 24-Mar-05
VISHAY
iil300_16
To Control
R3 =
R1 = R2
Input
V
I
PI
b
(
=
Figure 16. Isolated Control Amplifier
V
100 A
V a
MONITOR
3 V
ISO
AMP
+1
+
-
= 30 K
- 1
)
R2
R1
17165
Voltage
Monitor
17164
Fq
= 12 mA. Fig-
Fq
is found to
The value of R5 depends upon the IL300 Transfer
Gain (K3). K3 is targeted to be a unit gain device,
however to minimize the part to part Transfer Gain
variation, Infineon offers K3 graded into ± 5 % bins.
R5 can determined using the following equation,
Or if a unity gain amplifier is being designed (VMON-
ITOR = VOUT, R1 = 0), the equation simplifies to:
R5 =
R5 =
V
MONITOR
V
K3
R3
OUT
R3(R1 + R2)
17190
R2K3
Vishay Semiconductors
17166
www.vishay.com
IL300
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