Analog input higher than VDD1

Allen Du

Part Number: ISO224
Other Parts Discussed in Thread: OPA301,

Hi Team,

I plan to buy a ISO224EVM borad for test, I have some questions need your help, thanks in advance.

1. If VDD1 is 5V, can analog input be 12V and higher than VDD1?

2. if VDD1 is generated from VDD2, analog input ground needs to be connected with GND1, for example, analog input is devided from 400VDC, then ground of 400VDC should connect with GND1, right?

3. The Voltage signal I want to measure is 10us pulse, I simulated the circuit with TINA , the amplier on EVM board looks response is too slow, I changed to OPA301, but output has distortion, could you help have a look what the reason, thanks.

1222.ISO224 COPY.TSC

over 2 years ago

0 Tom Hendrick over 2 years ago

TI__Guru**** 171076 points

Hi Allen,

Thank you for taking a look at our ISO224! For your questions:

Yes, the input of the ISO224 can be up to +/-12V with a 5V VDD1 supply.
On the high side, your 400V source is divided down and fed to the ISO224 input. Your 400V source is referenced to GND1 in this case which is correct.
In the TINA simulator, rather than choose the 'Zero Initial Values' option in the Transient Analysis, use the 'Calculate operating point' option and see if that takes care of the initial 'blip' you see from the OPA301.