Megasquirt A/D Vdd

[Eric Fahlgren]

Stewart Prince wrote:
> 
> Just wondering about the megasquirt reference voltage for the  sensors and the
> a/d converter.  I Believe the lm29x7 has a +/-5% tolerance which would be about
> +/-.25 volts in terms of the absolute maximum ratings.  Is that accurate enough
> for the a/d converter & sensors?  Isn't a precision voltage reference with about
> a +/-1% usually used?

Stewart,

Supply precision doesn't matter since the sensors and adc use
the same reference voltage.  Taking TPS as an example, when
it is at 50% position, the (8-bit) adc count will be ~127 whether
the supply voltage is 5 or 10 or whatever, everything's kosher
as long as the supply is stable.

Eric

-- 
Eric Fahlgren                            Mechanical Dynamics, Inc
efahl at adams.com                          Ann Arbor, Michigan, USA
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