ADC0816 datasheet(11/13 Pages) NSC

11 / 13 page

Applications Information (Continued)

3.0 CONVERTER EQUATIONS

The transition between adjacent codes N andN+1is given

by:

(2)

The center of an output code N is given by:

(3)

The output code N for an arbitrary input are the integers

within the range:

(4)

where: V

IN = Voltage at comparator input

REF = Voltage at Ref(+)

REF = Voltage at Ref(−)

TUE = Total unadjusted error voltage (typically

REF(+) ÷512)

4.0 ANALOG COMPARATOR INPUTS

The dynamic comparator input current is caused by the

periodic switching of on-chip stray capacitances These are

connected alternately to the output of the resistor ladder/

switch tree network and to the comparator input as part of

the operation of the chopper stabilized comparator.

The average value of the comparator input current varies

directly with clock frequency and with V

IN as shown in Figure

If no filter capacitors are used at the analog or comparator

inputs and the signal source impedances are low, the com-

parator input current should not introduce converter errors,

as the transient created by the capacitance discharge will die

out before the comparator output is strobed.

If input filter capacitors are desired for noise reduction and

signal conditioning they will tend to average out the dynamic

comparator input current. It will then take on the character-

istics of a DC bias current whose effect can be predicted

conventionally. See AN-258 for further discussion.

DS005277-15

FIGURE 13. Symmetrically Centered Reference

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