ISO1212: Wide Input Range

Part Number: ISO1212

Dear Team,

Customer would like to design the ISO1212 for detection voltage input. With 12 to 120vdc and 230Vac input option in metro project
There are some questions related to the ISO1212's performance and design.

1. Can it working when minimum 12V and 230VAC voltage input .

Best Regards
Nhat Dao

• Hi Nhat:

Thanks for your interest in ISO1212!

Yes, ISO1212 can work down to 9VDC and works up to 300VAC. Please refer to datasheet section 9.2.1.2.4 for two example circuit techniques when designing for input voltage ranges that exceed 60V.

Also, you may find the following material useful.

How to Design Isolated Comparators for ±48V, 110V and 240V DC and AC Detection

ISO121x Threshold Calculator for 9V to 300V DC and AC Voltage Detection

Regards,

Dushmantha

I tried to read the datasheet, tech note many times but I can't complete calculating 9VDC to 300VDC voltage input. Can you help me calculate Rthr, Rshunt.

• Hi Nhat,

Please note that the input HIGH and LOW thresholds for ISO1212 are set by external resistors RTHR and RSHUNT. Since these thresholds are set by the resistors, the thresholds are going to be at fixed voltages for given resistor values.

For example, consider a design with RTHR = 40kΩ, RSHUNT = 22kΩ and RSENSE = 560Ω. This design accepts an input voltage of upto 240V with fixed LOW and HIGH thresholds of 110V and 113V, respectively. Here the input voltage can be anywhere from 0V to 240V but the device ISO1212 will detect any voltage less than 110V as LOW and voltage higher than 113V as HIGH.

To support different threshold voltages, you would have to modify the resistor values. Let me know if you have any questions, thanks.

Regards,
Koteshwar Rao

• Hi Koteshwar Rao
Thank you
I need a detect voltage circuit from 12V to 300VDC isolator. so that the MCU can read the state with or without electricity
Do you have a solution for my case?

• I found a solution on the internet that I don't know if it can be used in my case