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adc conversion with high output voltage
I would like to find a good way in order to do an adc conversion ( a circuit that i would link to a card)
i would like to have in the entry of my circuit an analog input of 400V, and i have a digital output of 3.3V ( that is present in my card), of course i would like a secure' way (isolation if possible) in order not to destroy my card ^ ^.
I've seen on internet, but i've not really found a way to do it.
Is there any TI component and a model of circuit that would help me to realize this?
In fact while i'm writing these lines i'm realizing that i'm still mixing between analog and digital I/O (can anyone help undestand this point please).
Thank you for your attention
what is there to understand?
if you are desinging I/O cards for a PLC (programmable logic controller) you will have to distinguish between digital inputs and outputs and analog inputs and outputs.
The HVS885 is a digital input chip whose eight 24V digital inputs are latched parallel inot a shift-register and clocked out serially via a digital isolator into a micro controller.
The 400V analog input(s) are best accomplished by resistive voltage dividers feeding into a +/- 10V SAR-ADC or 5V delta-sigma ADC, whose low-volt digital output can be fed via a digital isolator into a micro controller. Unfortunately we don't have an integrated design or one-chip solution. You will need to accomplish this function with discrete components.
does this help you further?
I recommend consulting our data converter forum as they can help further with the appropriate components.
I have been calculating a little and voila, here is the 400V (+/- 200V) isolated analog input you desired. Please note that the design of Rin = 942k might require two resistors to make up the value, depending on the standoff or breakthrough voltage of the resistors you are using. Typical breakthrough voltages range from 50V, 75V, 100V, 150V and 200V. Manufacturers of high-voltage passives are Vishay and NOVA.
The +/- 200V are divided down to a +/- 1.32V around a 1.65V mid-point for 0V input. Thus the upper, middle, and lower ADC input voltages are 0.9, 0.5, and 0.1 x Vref. With Vref = 3.3V the absolute voltages are 2.97V, 1.65V, and 0.33V respectively.
Good luck with your design. - Best regards, Thomas
Thanks Thomas Kugelstadt for your help
I really like your solution. On top of that there is isolation ^^
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