IC FOR OPTO DETECTOR
AM 336
close as possible to the pin to prevent noise. Also, in case of high emission-currents, blocking
capacitors against VCC are useful.
The comparator signals are taken over into the flip–flops with the positive slope of the IRD–signal.
Connections pins: IND, RD, RH
OUTPUT STAGES:
There are two antivalent output drivers for external PNP Darlington transistors with a current
limitation and periodical shut down in case of overload (short circuit protection).
The output signal of the internal flip-flop A (depending on VTA) controls the output drivers. They
consist of current sources which are attached to an internal pull-up resistor. The voltage drop at the
resistor RS, produced by the loading current, is compared with an internal voltage and is used to
limit the loading current. When limitation occurs, the external capacitor CSC is discharged and by
reaching the internal threshold both output drivers are switched off. After loading the capacitor CSC
is discharged and by reaching the threshold both output drivers are switched off. After charging the
capacitor CSC to the upper threshold the output stages are enabled again.
Unused outputs have to be attached to VCC. External PNP Darlington transistors have to be used so
that the necessary potential (VCC–2 × VBE) is available at the outputs in order to limit the loading
current.
Connection pins : QO, QC, RS, CSC
LED DRIVER:
The push–pull driver for the LED indicates the different ranges of the window–comparator or short
circuit of the output stages.
Following conditions are possible:
A
X
L
B
X
L
SC
L
LED
T1
short circuit, input voltage at IND has no effect
input voltage at IND is higher than VTA and VTB
input voltage is higher than VTA, but smaller than VTB
input voltage is smaller than VTA and VTB
H
L
L
H
H
H
T2
H
H
H
Tabelle 3: LED indications
Blinking frequencies for LED:
T1: oscillator frequency for devided by 128
T2: oscillator frequency for devided by 512
Connection pin: LED
analog microelectronics
February 2005
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AME [ ANALOG MICROELECTRONICS ]
