ic-wt iC-Haus, ic-wt Datasheet - Page 8

• Manufacturer Part Number: ic-wt
• Description: Incremental Encoder
• Manufacturer: iC-Haus

If the current from ILR is the same as the current from IZ, a common resistor with the value R
/ 2 can be utilized (in the example, 15.25 k
Limiting the current for the transmit LED
The resistance R
voltage V
(electrical characteristics No.603) and the permissible transmit current for the driver output I(LED)
characteristics No.602):
Example: R
The lowest value for the current limiting is obtained by inserting the maximum saturation voltage of the LED pin
Vs(LED)
Example: I(LED)
The limiting value inserted for the saturation voltage Vs(LED)
50mA. The real minimum value for current limiting is therefore a little higher.
Capacitor at CLR
The value of capacitor C
of control. The following applies:
Upwardly, the value is limited by the dead time
voltage:
Example: = 100ms, R
PRINTED CIRCUIT BOARD LAYOUT
The following aspects should be noted when creating the PCB layout:
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iC-WT
INCREMENTAL ENCODER
Short connections between photodiodes array and iC-WT to minimize couplings and interference on the
small photocurrents.
Short-circuit the anodes of the photodiodes to pin AGND of the iC-WT. The connection to GND is made
exclusively inside the chip.
Switch R
Do not run the printed conductors of the outputs of iC-WT and iC-WE in the vicinity of the connections
between photodiodes array and iC-WT or decouple by means of a GND conductor between them.
Connecting point of a metal reticle for the photodiodes array is GND on the iC-WT.
R
I ( LED )
C
C
LED
LR , min
LR , max
max
fw,min
lim
and the maximum LED forward voltage V
VCC
LR
LED
1 nF
0.25
, R
of the LED used for illumination, the minimum saturation voltage of the LED pin Vs(LED)
= (5.5V - 1.2V - 0.4V) / 50mA = 78
VCC
R
max
Z
lim
LED
, C
R
LR
= (4.5V - 1.5V - 1.2) / 78
LR
min
15 k
LR
limits the maximum current through the LED. It is calculated with the minimum forward
I ( LED )
V
to AGND too.
LR
fw , min
LR
= 15k : C
V
is not critical. The bottom of the permissible value range is restricted by the stability
fw , max
R
max
LED
Vs ( LED )
Vs ( LED )
LR,max
min
= (0.25
max
/ 2 = 7.625 k ). ILR is connected directly to IZ.
19mA
100ms) / 15k
of the LED current control after switching on the supply
fw,max
:
max
of 1.2V is not achieved by currents under
1.5 F
Rev A0, Page 8/13
LR,Z
= R
max
LR
(electrical
/ 2 = R
Z