Looking at the schematic for Marbles (but I think this applies to most of the more recent MI modules) on the Inputs page, I can see how the MCP6004 op-amp is used to scale and possibly clip incoming CV signals, so that the module can accept signals in the -5v to 5v range, and the microcontroller only received 0v - 3.3v.
It seems to me that these inputs work as follows: Each op-amp is set up as a mixer which mixes an offest into the incoming CV signal, which is then scaled by setting the gain of the op-amp using the feedback resistors. The op amp is a rail to rail op amp, with the supply voltage set to be the same as the microcontroller, so the op amp can’t produce an output outside the range that the microcontroller can accept.
Looking at the MCP6004 datasheet under absolute maximum values it lists the following:
Analog Inputs (VIN+, VIN-)††… VSS – 1.0V to VDD + 1.0V
Which means that the chip can only accept input voltages between -1V and 4.3V.
So my question is: what happens when someone plugs something into the module with a high or low voltage, i.e. -10v, +12v etc.?
I have learnt an absolutely huge amount from looking at the Mutable Instruments schematics but I’ve not been able to figure this one thing out!