AM336 datasheet(7/12 Pages) AD

7 / 12 page

IC FOR OPTO DETECTOR

AM 336

analog microelectronics

February 2005

7/12

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:

LED

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

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

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