Analog Isolator for ADC input

[freemanantony]

hai everyone,
I am searching for an analog isolator ic that receives voltage as input and gives voltage as output,does anybody have an idea on analog isolator?

 

[kripacharya]

an optocoupler is one possibility.
but you have to say more detail about what are your voltage levels etc.

 

[crutschow]

How much isolation impedance do you need?
What is the maximum voltage difference it will need to isolate?
What is the signal voltage.

 

[freemanantony]

i am planning to give 0 - 3.3v as input to analog isolator and expecting the same voltage levels in the output side to be given to the input of ADC of microcontroller

 

[picgak]

if your analog voltage is not fast changing you can use a lamp and LDR to transform it to the other side
otherwise there are High-Linearity Analog Opto-couplers available. These devices consist of a high performance LED that illuminates two closely matched photodiodes. The
idea is to use one of the photodiodes as a monitor of the LED light output and, using feedback, stabilize and eliminate the drift and non-linearity of the LED . Avago Technologies HCNR200 and HCNR201 High-Linearity Analog Opto-couplers

 

[alexan_e]

I think IL300 can do what you want https://www.vishay.com/docs/83622/il300.pdf

 

[tpetar]

ISO122 is low cost isolation amplifier
https://www.ti.com/lit/ds/symlink/iso122.pdf

IL300 in my country is over 5eur, and ISO122 is 0,33eur. Of course IL300 is great solution.

Correction: Price of 0,33eur is not correct I mix with some other part prices! I apologize for that. For this part should prepare lots more money.

 

[FvM]

ISO122 is 0,33eur.

Really? It's about 18 EUR at Digikey.

 

[tpetar]

Yes I saw now that princes, I probably mix price for ISO122 with price of some optocoupler part.

What to say I apologize for this pricing mess. I hope that someone dont go to market to buy this for 0,33eur per piece.

Thanks FvM for correction.

 

[alexan_e]

Really? It's about 18 EUR at Digikey.

We have a golden opportunity to make business by reselling components bought from Serbia :wink:

TI prices start from about $12 and upwards from 1000pcs
https://www.ti.com/product/iso122

 

[tpetar]

For my friends special discount.

 

[kripacharya]

We have a golden opportunity to make business by reselling components bought from Serbia :wink:

aaaahh.... i already bought my tickets :-(

 

[tpetar]

Who knows maybe they will reduce prices, when saw lots of peoples in front of building, in "I whant to buy iPhone" style.

 

[freemanantony]

instead of il300 can i use 4n33?

 

[alexan_e]

IN 4n33 there is no mechanism that can be uses so that the output level equals the input level, if this is not a problem then yes.

 

[crutschow]

IN 4n33 there is no mechanism that can be uses so that the output level equals the input level, if this is not a problem then yes.

Also the output voltage is not a linear function of the input voltage.

 

[KonstanU]

To topicstarter.
You wrote nothing about isolation voltage and required frequency.
But the next idea can help you.
Use bunch of : input - resistive divider - OPA - HCPL-7840 - OPA - ADC

 

[freemanantony]

if i am using il300 can i directly give the signal without using opamps

 

[alexan_e]

And how do you intent to adjust the input/output levels to match?

 

[FvM]

IL300 isn't a complete analog isolator, it's a building block that must be supplemented by OPs to perform the intended function. In some cases, the I/V conversion at the secondary side may be achieved by a resistor, but an OP/error amplifier on the primary is essentially required.