uc32 components missing

[john_m0ers]

Hi,

Out of curiosity, can someone tell me why two capacitors are missing off the chipkit uc32 boards marked C7  and C9? On the schematic they are marked with  "no load".

In the datasheet it says that 10uF tantalum or low esr electrolytics are needed for stability if the regulators are far from the power source. Does this mean they are needed, because they could be quite a distance away using usb, or a wall wart type supply?

Regards,  john

 

[jpeyron]

Hi @john_m0ers,

We reached out to a design engineer and they responded that we designed this circuit to allows us to load a variety of regulators. We can either load a “fixed” regulator OR a variable adjust regulator with merely a parts change. Also, for the input/output cap, some regulators call for caps with an certain ESR to be stable, that can either be a ceramic with a resistor OR a tantalum or electrolytic with inherent ESR. Again, here we loaded the ceramic with a resistor (where needed). While it is possible to use the one cap location, 2 locations allows for 2 sizes of caps as electrolytics tend to be larger than ceramics. If you notice, both of the “No Load” caps on the schematic have a + on the top; that is specifying the orientation for a polarized cap such as an electrolytic. In the end we decided to go with the stable ceramic with a resistor solution.

thank you,

Jon

[john_m0ers]

Thank you for that info, that clears that one up.

regards john