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Re: Serial port power draw.

James Davidheiser <> wrote:
<snip> 
> ... They say nothing about doing this with the MAX232. Does
> that mean I will need to power the MAX232 off of something other than
> the serial port? Does a max232 draw more power, where it would exceed
> the spec of no more than 5mA? A 16c71 draws about 2mA; I can't expect
> that the MAX232 would draw more than 3, am I wrong? Am I missing some
> other crucial point here?

I checked the data sheet 
http://www.elfa.se/pdf/73/730/7302326.pdf
and it says that:

Operating voltage: 4.5 - 5.5 V
							typ	max
No load:		max220				0.5	2	mA
			max222/232A/233A/242/243	4	10	mA
dual 3 Kohm load:	max220				12		mA
			max222/232A/233A/242/243	15		mA

The component based alternative of yours probably works directly
at the higher RS232 voltage and therefore uses less current. These
Max RS232 drivers contain builtin power supplies which generate
these higher voltages needed by capacitor switching.

If I understand you correctly you intend to power the PIC, which
wants 5 V as well I guess, from the serial port. In that case you
may consider using some efficient step down converter like MAX 1626 
http://www.elfa.se/pdf/73/730/7302326.pdf

	Best regards
	Roland

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