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Looking for a very accurate voltage controlled PWM duty cycle chip or circuit

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AQUAMAN:
I have data from an NTC and RTD that I need to pass over an isolation.

What I am thinking of doing a normal voltage divider for both and then turning this voltage into a duty cycle or frequency signal to pass through a digital optocoupler. Probably looking at about 10kHz

In designing this circuit money is my least concern, but footprint (both height and area) and accuracy are my main requirements. I need it to be very accurate and and I need the components height less than 2.5mm. So for resistors, caps, NTC and RTD I'm using 0603 or 1005 SMD.

I have been looking at LTC6992 (https://www.analog.com/media/en/technical-documentation/data-sheets/LTC6992-1-6992-2-6992-3-6992-4.pdf)
I like this chip, it's easy to use, small footprint, but I worry it will not be accurate enough. It says plus minus 4.5% accuracy in the datasheet. It is also only 0.1-0.9V control voltage so I think it makes my readings from NTC and RTD more susceptible to noise because I have to lower the sensing current to get it to this level

Are there any other ICs like this, or would I be better off trying to find op amps in small footprints - or would to do it all on a small micro controller like ATTINY85 by better?

jmelson:
Would a voltage to frequency converter be better?  There can be some distortion of pulse widths when passed through optical isolators.

Jon

ogden:

iMo:
https://www.analog.com/en/parametricsearch/11101
http://www.ti.com/isolation/isolated-adcs/products.html?pqs=paqs&familyid=2021#

ogden:
Besides mentioned isolated ADC solutions other way would be to use generic (i2c or SPI) SD ADC with bus isolator. Also there is "programmable SD ADC", msp430f2013. Any (discrete) voltage to PWM or frequency converter will be much less accurate than ADC isolation approach.

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