Datasheet

ADC0816, ADC0817

www.ti.com

SNAS527C –JUNE 1999–REVISED MARCH 2013

Additional single-ended analog signals can be multiplexed to the A/D converter by disabling all the multiplexer

inputs using the expansion control. The additional external signals are connected to the comparator input and the

device ground. Additional signal conditioning (i.e., prescaling, sample and hold, instrumentation amplification,

etc.) may also be added between the analog input signal and the comparator input.

CONVERTER CHARACTERISTICS

The Converter

The heart of this single chip data acquisition system is its8-bit analog-to-digital converter. The converter is

designed to give fast, accurate, and repeatable conversions over a wide range of temperatures. The converter is

partitioned into 3 major sections: the 256R ladder network, the successive approximation register, and the

comparator. The converter's digital outputs are positive true.

The 256R ladder network approach Figure 1 was chosen over the conventional R/2R ladder because of its

inherent monotonicity, which specifies no missing digital codes. Monotonicity is particularly important in closed

loop feedback control systems. A non-monotonic relationship can cause oscillations that will be catastrophic for

the system. Additionally, the 256R network does not cause load variations on the reference voltage.

The bottom resistor and the top resistor of the ladder networking Figure 1 are not the same value as the

remainder of the network. The difference in these resistors causes the output characteristic to be symmetrical

with the zero and full-scale points of the transfer curve. The first output transition occurs when the analog signal

has reached + ½ LSB and succeeding output transitions occur every 1 LSB later up to full-scale.

Figure 1. Resistor Ladder and Switch Tree

Figure 2. 3-Bit A/D Transfer Curve Figure 3. 3-Bit A/D Absolute Accuracy Curve

Product Folder Links: ADC0816 ADC0817