ADC0804LCWM datasheet(22/48 Pages) TI

22 / 48 page

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 k

Ω. 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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ADC0804LCWM 数据表(PDF) 22 Page - Texas Instruments