ADC0804LCWM datasheet(15/56 Pages) TI1

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ADC0801, ADC0802, ADC0803, ADC0804, ADC0805

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SNOSBI1C – NOVEMBER 2009 – REVISED JUNE 2015

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

9.1 Application Information

The following sections give example circuits and suggestions for using the ADC080X in typical application

situation with a typical 8-bit micro-processor.

9.1.1 Testing the ADC Converter

There are many degrees of complexity associated with testing an ADC converter. One of the simplest tests is to

apply a known analog input voltage to the converter and use LEDs to display the resulting digital output code as

shown in Figure 23.

For ease of testing, the VREF/2 (pin 9) should be supplied with 2.560 VDC and a VCC supply voltage of 5.12 VDC

should be used. This provides an LSB value of 20 mV.

If a full-scale adjustment is to be made, an analog input voltage of 5.090 VDC (5.120–1/⁄2 LSB) should be applied

to the VIN(+) pin with the VIN(−) pin grounded. The value of the VREF/2 input voltage should then be adjusted until

the digital output code is just changing from 1111 1110 to 1111 1111. This value of VREF/2 should then be used

for all the tests.

The digital output LED display can be decoded by dividing the 8 bits into 2 hex characters, the 4 most significant

(MS) and the 4 least significant (LS). Table 1 shows the fractional binary equivalent of these two 4-bit groups. By

adding the voltages obtained from the "VM" and "VLS" columns in Table 1, the nominal value of the digital

display (when VREF/2 = 2.560V) can be determined. For example, for an output LED display of 1011 0110 or B6

(in hex), the voltage values from the table are 3.520 + 0.120 or 3.640 VDC. These voltage values represent the

center-values of a perfect ADC converter. The effects of quantization error have to be accounted for in the

interpretation of the test results.

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