iC-OV

5-BIT OPTO ENCODER

Rev C0, Page 8/9

Fig. 2: Wiring the testing aid

Tracks 1..5

The threshold IS of the current comparators for tracks C1 to C5 is determined by the resistor RSET and is about

0.5 x ISET. The threshold is supplemented by the amplified current of compensation diode DDC to compensate

for the dark currents of photodiodes D1 to D5 and the amplifier input currents. The hysteresis of the current

comparators enhances the interference immunity.

Track 1 can be inverted by connecting pin NINV to ground (GND). If the pin remains open, the internal pull-up

current source generates a high level. When the Gray Code is used, inverting the MSB track is the equivalent to

reversing the movement.

Fault message in case of overtemperature or undervoltage

When the chip temperature is too high or the voltage too low, the push-pull output stages are switched to a

high-impedance state and the error state is signalled to the message circuit (block: Error). Both monitoring

circuits operate with hysteresis; NER= low remains until the cause of the error has been eliminated.

Violating the limits of the LED current control range also generates a low signal at the open collector output NER.

APPLICATIONS INFORMATION

Wiring the Test Aid

To activate the test aid integrated into the iC-OV, the current threshold defined in the Electrical Characteristics

No. 403 must be exceeded at both pins TREF and TNRF. This activates the testing aid which does not switch

back off until the current drops below approx. 1µA.

A clamping circuit as per Fig. 2 also prevents a brief drop below the cut-off threshold. A changeover switch can

be used to reverse the output polarity of the iC-OV.