adc0800pd National Semiconductor Corporation, adc0800pd Datasheet - Page 7

• Manufacturer Part Number: adc0800pd
• Description: 8-bit A/d Converter
• Manufacturer: National Semiconductor Corporation

ure 3 Note that the LED drivers invert the digital output of
Typical Applications
TESTING THE A D CONVERTER
There are many degrees of complexity associated with test-
ing an A D 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 Fig-
the A D converter to provide a binary display A lab DVM
can be used if a precision voltage source is not available
After adjusting the zero and full-scale any number of points
can be checked as desired
For ease of testing a 10 24 V
for the A D converter This provides an LSB of 40 mV
(10 240 256) To adjust the zero of the A D an analog input
voltage of
LSB or 20 mV should be applied and the
DC
reference is recommended
(Continued)
FIGURE 4 Complete Basic Tester Circuit
FIGURE 3 Basic A D Tester
7
4 Note that the clock input voltage swing and the digital
zero adjust potentiometer should be set to provide a flicker
on the LSB LED readout with all the other display LEDs
OFF
To adjust the full-scale adjust potentiometer an analog in-
put that is 1
or 10 180 V
the full-scale adjusted for a flicker on the LSB LED but this
time with all the other LEDs ON
A complete circuit for a simple A D tester is shown in Figure
output voltage swings are from 0V to 10 24V
MM74C901 provides a voltage translation to 5V operation
and also the logic inversion so the readout LEDs are in bina-
ry
DC
) should be applied to the analog input and
LSB less than the reference (10 240 – 0 060
TL H 5670 – 15
TL H 5670 – 7
The