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ISO1212: Minimum input current

Part Number: ISO1212
Other Parts Discussed in Thread: ISOM8110

Dear ISO team,

in our application we have to check, if mains voltage (230 VAC) is above a specific level and want to use the ISO1212 for this.

There is a schematic available in document TIDMB97.PDF, where the ISO1212DBQR is used to measure mains voltage.

In our application we have to take care about touch currents, for this reason the total resistance of the voltage divider needs to be about 1 MOhm.

This limits the input current that can flow into the pins SENSEx and INx into the 100µA range.

What is the minimum current that has flow into the SENSEx and INx pins so that the chip stays functional?



  • Gerhard, 

    The ISO1212 and digital input devices in our portfolio are designed to operate according to IEC61131-2. The minimum input current for these devices is 2.25mA (typ).

    This standard defines input types 1-3. As shown in the above datasheet figure, the field side input would need to be in the "ON" region for a logic high on the output. You can read more about setting the input currents in Setting Current Limit and Voltage Thresholds and calculate the thresholds using the following calculator (direct download link) ISO121x Threshold Calculator for 9V to 300V DC and AC Voltage Detection

    Alternatively, you could evaluate the opto-emulators (see ISOM8110) which has a 500uA turn on current that can be used to sense the grid input. This will get you closer to the 100uA input current that is needed.