ES5136

3 1/2 DIGIT A/D CONVERTER W/LCD(Low power)

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4.Phase 4, Zero Integrate (ZI)

During zero integrating, the reference capacitor is charged to the

reference voltage and input low is shorted to analog common. At the

same time, a feedback loop is closed around the system to input high

to cause the integrator output to return to zero so that the overrange

hangover of the integral capacitor can be eliminated.

5.Differential Input

The input voltage can be any differential voltages, but must be within

the common mode range of the input amplifier(buffer). The voltage

range is from 0.5 volts below the positive supply to 1.0 volt above the

negative supply. In this range the CMRR of the system is 86dB

typical. Since the integrator swings with the common mode voltage, it

must be assured that the integrator output does not saturate.

6.Differential Reference

The reference inputs are floating, and the only restriction on the

applied voltage is that it should lie in the range of the owner supply

voltage of the converter. The roll- over voltage caused by the reference

capacitor losing or gaining charge to stray capacity on its nodes is the

main source of common mode error. In a large common mode

condition, the reference capacitor will gain extral charge(increase

voltage)when deintegrates a positive signal but lose charge(decrease

voltage)when deintegrates a negative input signal. The difference in

reference for positive or negative input signal will give a roll-over

error. By selecting the reference capacitor large enough in comparison

to the stray capacitance, this error can be held to less than 0.5 count for

the worst case condition.