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Power to F28027 in Standalone Mode

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I am currently running a code that measures the voltage through the ADCINA4 pin (J1.6) and displays the results on a LCD screen. I am manually changing the voltage with a potentiometer. I am doing this two ways:


First, I used a USB to power the LaunchPad and viewed the results on Code Composer Studio (the LCD also displays the results viewed in Code Composer Studio simultaneously).


Second, I used a battery (with a 3.3 V voltage regulator) to power the LaunchPad in standalone mode using the J3 pins (on the bottom right-hand side of the LaunchPad). Also noteworthy, I have f2802x_codestartbranch.asm and F28027.cmd in the project. Also, I put the third S1 switch in the down position in this standalone mode and all jumpers are connected.


I compared the results of the C2000 LaunchPad with those on the DAQ (or multimeter...either works) and they are much more accurate and consistent when the LaunchPad is being powered with the USB. 


I looked for documentation on how to power the F28027 in standalone mode and I haven't seen anything so far. I would be greatly appreciative to be directed to a place where I could do more reading on powering the F28027 in standalone mode. Of course, suggestions on how to improve my setup are greatly appreciated as well.

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I measured the current going to the LaunchPad with a multimeter and it was 155 mA. I read from the data sheet on the TI website (http://www.ti.com/lit/ds/sprs523j/sprs523j.pdf) that the max current consumption is 100 mA. I have attached a plot of some of my results as well. The y axis is the difference between the mean DAQ and LaunchPad values (in mV). Still trying to figure it out.

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  • 1 month later...

Sorry for the slow response...


When powering the launchpad standalone just feed 3.3V into the pins as you are already doing.  You'll want to disconnect JP1, 2, and 3.  These jumpers supply USB power to the F28027 device on the LP.  If these jumpers are connected when the board is powered externally they feed power back into the emulator section.  I suspect this may be what was causing the trouble.


In regard to current consumption, the max power use of the F28027 is indeed around 100mA, but there are many other things on the board that consume power.  The main culprit I suspect is the FTDI device in the emulator.

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