ADC0801, ADC0802
ADC0803, ADC0804, ADC0805
SNOSBI1B –NOVEMBER 2009–REVISED FEBRUARY 2013
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Noise
The leads to the analog inputs (pins 6 and 7) should be kept as short as possible to minimize input noise
coupling. Both noise and undesired digital clock coupling to these inputs can cause system errors. The source
resistance for these inputs should, in general, be kept below 5 kΩ. Larger values of source resistance can cause
undesired system noise pickup. Input bypass capacitors, placed from the analog inputs to ground, will eliminate
system noise pickup but can create analog scale errors as these capacitors will average the transient input
switching currents of the A/D (see Analog Inputs — Input Current). This scale error depends on both a large
source resistance and the use of an input bypass capacitor. This error can be eliminated by doing a full-scale
adjustment of the A/D (adjust VREF/2 for a proper full-scale reading — see Full-Scale) with the source resistance
and input bypass capacitor in place.
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