Honored Contributor
Honored ContributorHi Lorenzo,
--- Quote Start --- My problem is assuring myself I can do this, so I need to know how much current DE2-115 can source on VCC3P3 node (so called on its schematics) and how much current is already sinked by the board and by the LTM through GPIO. How can I get these informations? --- Quote End --- The schematic has the part numbers and the data sheets have the maximum currents for each device. However, you've got to consider; 1) A 100-mil header can support at most 1A. How many of the 100-mil header pins are dedicated to 3.3V and ground? How much current does your external circuit need? 2) Find the 3.3V regulator and touch it. Is it hot/warm? If you draw current through the GPIO 3.3V pin, then the regulator will get warmer. Is it a linear regulator (it'll get a lot warmer) or switching regulator (its temperature won't change much)? 3) What is worth more to you; your DE115 board, or an external 3.3V supply? If the voltage regulator on the board supports say up to a 1A load, and you can estimate the current draw from the other components on the board, then you can determine what a safe level of current draw is. However, I would not recommend drawing anything over a few hundred mA, even if your analysis indicates you can draw more. Being conservative lets you keep your evaluation boards for much longer :) Cheers, Dave
