Help for schem mod (quantizer)

[fredrik]

The 5V pin (!), if you feed the unregulated voltage to VIN; see the drawing here:

Design glitches: Arduino Nano supply voltage

(thought I’d collect my nano supply notes in one place to make it easier to link to) A common design glitch in circuits that use an Arduino Nano is to connect regulated 5 V to the VIN pin instead of the +5V pin. This results in the Arduino running at a lower internal supply voltage, often 4 V or below, which may be a problem if the design depends on analog inputs or digital output levels. Voltages below 4.5 V are also out of spec for the 16 MHz clock used by the Nano. Details below, but TL;DR …

Not sure how well the onboard regulator is “heat sinked” on an average Nano, but an LM1117 has a thermal resistance of around 60 °C/W junction to air, so you have (125 − 25) / 60 = ~1.5 W to play with worst case, which at 12 V is 1.5 / (12 − 5) = just over 200 mA. You’d want a bit less because 125 °C is crazy hot, but otoh the PCB will distribute some of the heat over a bigger area.