From: "Frank Bemelman"
Subject: Re: Serial 12bit ADC: poor performances (or my mistake?)
Date: Mon, 11 Nov 2002 20:11:17 +0100
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"Alessandro" schreef in bericht
> I am testing a simple A/D serial converter
> based on a ADS7822 (12 bit serial).
> Vref=Vcc=2,5V (from a LM336-2,5).
> The clock pulse is given by a push
> button (latched by mean of a 4011).
Manually clocking the adc means it takes almost
forever to do a full conversion, and the clock
periods will have very different lenghts etc.
I don't know if I like that. Make sure you
have good decoupling capacitors fitted, and try
clocking it with a stable and preferably faster
clock than 1Hz ;)
> The voltage is variable between 0 and 2,5V;
> the results up to 1,0V are very good, but
> under this value the performances seems to
> be very poor.
Do you get the same readings over and over
again, or is the error random ?
> Are the above results typical
> for this ADC? I think they aren't
> so I was wondering where I have
No, the results look terrible. There must
be something wrong.
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