ADC0816, ADC0817

SNAS527C – JUNE 1999 – REVISED MARCH 2013

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Figure 4. Typical Error Curve

Timing Diagram

Figure 5.

The successive approximation register (SAR) performs 8 iterations to approximate the input voltage. For any

SAR type converter, n-iterations are required for an n-bit converter. Figure 2 shows a typical example of a 3-bit

converter. In the ADC0816,ADC0817, the approximation technique is extended to 8 bits using the 256Rnetwork.

The A/D converter's successive approximation register (SAR)is reset on the positive edge of the start conversion

(SC) pulse. The conversion is begun on the falling edge of the start conversion pulse. A conversion in process

will be interrupted by receipt of a new start conversion pulse. Continuous conversion may be accomplished by

tying the end-of-conversion(EOC) output to the SC input. If used in this mode, an external start conversion pulse

should be applied after power up. End-of-conversion will go low between 0 and 8 clock pulses after the rising

edge of start conversion.

The most important section of the A/D converter is the comparator. It is this section which is responsible for the

ultimate accuracy of the entire converter. It is also the comparator drift which has the greatest influence on the

repeatability of the device. A chopper-stabilized comparator provides the most effective method of satisfying all

the converter requirements.

The chopper-stabilized comparator converts the DC input signal into an AC signal. This signal is then fed through

a high gain AC amplifier and has the DC level restored. This technique limits the drift component of the amplifier

since the drift is a DC component which is not passed by the AC amplifier. This makes the entire A/D converter

extremely insensitive to temperature, long term drift and input offset errors.

Figure 4 shows a typical error curve for the ADC0816 as measured using the procedures outlined in AN-179.

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