MCP600x for CV inputs?

I have a question about MCP600x opamps.

I can see they are are used to condition CV inputs into the MCU on several Mutable Instruments designs. I saw posts on this forum that explain they are used because they are rail-to-rail, which makes sense. However the Microchip datasheet states that they have “a power supplyrange of 1.8V to 6.0V”; indeed e.g. on Rings they are powered up with 3.3V.

With Eurorack modules generating CVs ranging between say +/- 10V, or maybe even +/- 12V, I don’t understand how these opamps, rail-to-rail or not, are not potentially clipping when they are powered up with that kind of voltage?

The op-amps are not “powered” by the CV!

The op-amp is powered by 3.3V, and used in a circuit with a small gain. For example, the circuit used for Rings’ CV input has an output of 3.3V for a CV of -8V, and an output of 0V for a CV of +8V (so the gain is 0.2). Outside the [-8, +8] V range, the op-amp will clip.

Note that the inverting circuit used with the op-amp does not expose the CV to the input pins of the op-amps. Both pins stay at a ground voltage. The op-amp “senses” the CV through the very small current flowing through the 100k input resistor.

Indeed! Bad turn of phrase on my part sorry, I meant the power supply range stated in the datasheet.

OK thanks, that makes sense!