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Current required for a Propeller MCU — Parallax Forums

Current required for a Propeller MCU

solarprismsolarprism Posts: 23
edited 2010-12-01 19:00 in Propeller 1
I built a test circuit for Propeller, like the Protoboard.I ve read in the specification of Propeller that it required only 500uA for each MIPS and for the maximum MIPS can be 80MHZ/4*8=160MIPS, means that Propeller draw 80mA at most.We combine that with the EEPROM and 5V for pin 9 of VGA,total about 100mA so can i use a USB connector from PC to provide current and 5V and use LDO like AP1117 to convert to 3,3V to supply the whole board.

Comments

  • BigFootBigFoot Posts: 259
    edited 2010-12-01 18:40
    It is hard to estimate what the Propeller chip will draw, it all depends
    on how heavily you load the outputs.

    Our new PoS board is running dual propeller chips, two 16 bit I/O
    expanders a touch control chip, real time clock, 512K eeprom, Sd Card
    and a digi pot off the propellers 3.3v supply and the idle current draw
    is 75 ma for the first board and 77 ma for the other.
  • Mike GreenMike Green Posts: 23,101
    edited 2010-12-01 18:45
    It's more complex than that. For example, any current drained or sourced from an I/O pin is in addition to the figures mentioned. Also, the phase locked loop for the system clock takes some current. Read the datasheet carefully. The maximum allowed supply current is 300mA, so you should be fine with a USB power source.
  • solarprismsolarprism Posts: 23
    edited 2010-12-01 18:51
    BigFoot wrote: »
    It is hard to estimate what the Propeller chip will draw, it all depends
    on how heavily you load the outputs.

    Our new PoS board is running dual propeller chips, two 16 bit I/O
    expanders a touch control chip, real time clock, 512K eeprom Sd Card
    and a digi pot off the propellers 3.3v supply and the idle current draw
    is 75 ma for the first board and 77 ma for the other.

    Thank you for your information.
    I use one Prop(used 24 I/O pins) a AT24C512 eeprom with VGA port and 3 optocouplers, but now i want to test vga port so i loaded a program that affect only VGA pin (p16-P23) but no thing happen, so i wonder if there is not enough current.
  • BigFootBigFoot Posts: 259
    edited 2010-12-01 18:59
    The figures that I mentioned do not include any I/O devices and the 232 x 480 x16
    7" color lcd display and led backlight were not connected. The boards draw around
    550 ma in operation. The led backlight can draw 300 mA alone.
  • localrogerlocalroger Posts: 3,452
    edited 2010-12-01 19:00
    As a practical matter unless you are running very intensive threads on every cog none of which ever use WAITCNT, it's very unusual to see a Propeller draw more than 100 mA at 80 MHz. If you really want to overload your 3v3 regulator you need to add an ENC28J60 ethernet chip to the mix, those things are toaster ovens by comparison.
  • solarprismsolarprism Posts: 23
    edited 2010-12-01 19:00
    Mike Green wrote: »
    It's more complex than that. For example, any current drained or sourced from an I/O pin is in addition to the figures mentioned. Also, the phase locked loop for the system clock takes some current. Read the datasheet carefully. The maximum allowed supply current is 300mA, so you should be fine with a USB power source.

    opps my bad,it is only few lines above,so the power source is not the problem for my VGA test :mad:
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