View Full Version : Teensy 3 3.3 current

12-26-2012, 03:44 AM
I'd like to power a Pololu Wixel as a wireless serial extension from the 3v3 pin on my Teensy 3.0. The Wixel is a 3v device.

I can't find any information on how much current the regulator on the Teensy 3.0 will source. My apologies if I'm missing something obvious!

Can anyone help out with the current on that regulator?


12-26-2012, 04:46 AM
The mk20dx128vlh5 regulator can supply a total of 120 mA, but the CPU consumes some (about 16 mA at 48 MHz, about 8 mA at 24 MHz), and so does the bootloader CPU plus whatever other loads are on the pins (e.g. the LED is a few mA when on).

http://cache.freescale.com/files/32bit/doc/data_sheet/K20P64M50SF0.pdf?fsrch=1&WT_TYPE=Data Sheets&WT_VENDOR=FREESCALE&WT_FILE_FORMAT=pdf&WT_ASSET=Documentation&sr=1 -- page 45 shows the 120 mA max. load

Conversely, the specs for the Pololu Wixel don't list a maximum current consumption -- I would guess about 50 mA -- so, if you don't have any other significant loads on the 3.3 V supply, you are probably OK.

Note the Wixel can also run from a 2.7 to 5.x V supply, and also regulates its own 3.3 V -- you might get into strange power up/down issues if you do power each device separately from a 5 V supply (and they are connected via I/O lines) -- I guess you are going to power the Wixel from the Teensy's 3.3 V regulator ? -- from reading its schematic, that means it gets a supply 0.7 V (diode drop) lower than that value; I don;t know what component it uses for its LDO, but you might be able to just power the Wixel directly via its 3V3 pin, but then don't apply USB or VIN to it (or the two 3.3 V regulators will fight (probably OK, but you can't be sure)).