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LPC11U24 ADC problem

Topic last updated 03 Jul 2012, by Kevin Hobbs. 1 reply
Marc ROBERT
02 Jul 2012

Hello, I have a problem with my LPC11U24. I use p19 and p20 to compare two tensions and I command an output p21 and p22 in function off the result. When I use USB alimentation, the program work correctly. When I use Vb pin with 2.9V, the program doesn't work correctly. The two tensions in p19 and p20 are about 1,9V to 2V Anywone have a solution? Thanks

Kevin Hobbs
03 Jul 2012

Haven't used this module, but Vb was the battery backup on the RTC on the 1768, but your part doesn't have that!

Looking at the schematic

http://mbed.org/media/uploads/chris/mbed-010.2-schematic.pdf

I would have expected Vb to be at least 3.3Volts to simulate the other power options. Also note that no external 3.3V supply at pin40 is available (as was the case when USB powered).

If you don't get a better answer my advice is to try a power supply to Vin (pin 2) and gnd (pin 1) of say 5V and see if this works