1 reply to this topic

[cakalapati]

Hi everyone. I'm looking at the schematics between the Netduino Plus and the Netduino Plus 2 boards. Can anyone tell me why the two boards have a different input for the VIN_COMP_LOGIC (see attached image)? Charles

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•  netduino-plus-plus2-schematic-VIN_COMP_LOGIC.png   64.62KB   24 downloads

[Mario Vernari]

My guess, Charles, is about the range of the Vin. In the "old" N+, the Vin-side divider halves the voltage applied. Since the reference is +3.3V, the equivalent Vin should be +6.6V. Below this threshold, the Vin supply is disabled. The question is: how much is the maximum Vin? Well, when Vin gets higher than +10V, the voltage on the non-inverting pin would be higher than +5V. However, that is a dangerous level, because the op-amp is powered exactly at +5V. The op-amp specs says that the max voltage on any input is +0.ò1V above its positive supply. I think that they notice this issue, and changed a little bit the comparation pattern on the N+2. BTW, on the new board the range is spanning from +6 to +12V. Cheers