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Analog Isolator for ADC input

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Member level 4
May 19, 2010
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Chennai, India
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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?

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

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

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

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
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ISO122 is low cost isolation amplifier

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.
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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.

:oops: :)

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

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.

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

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

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.

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