ADC08034 National Semiconductor, ADC08034 Datasheet - Page 10

• Manufacturer Part Number: ADC08034
• Description: 8-Bit High-Speed Serial I/O A/D Converters with Multiplexer Options/ Voltage Reference/ and Track/Hold Function
• Manufacturer: National Semiconductor

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ADC08038 Functional Block Diagram
Functional Description
1.0 MULTIPLEXER ADDRESSING
The design of these converters utilizes a comparator struc-
ture with built-in sample-and-hold which provides for a differ-
ential analog input to be converted by a successive-
approximation routine.
The actual voltage converted is always the difference be-
tween an assigned “+” input terminal and a “−” input terminal.
The polarity of each input terminal of the pair indicates which
line the converter expects to be the most positive. If the as-
signed “+” input voltage is less than the “−” input voltage the
converter responds with an all zeros output code.
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A unique input multiplexing scheme has been utilized to pro-
vide multiple analog channels with software-configurable
single-ended, differential, or pseudo-differential (which will
convert the difference between the voltage at any analog in-
put and a common terminal) operation. The analog signal
conditioning required in transducer-based data acquisition
systems is significantly simplified with this type of input flex-
ibility. One converter package can now handle ground refer-
enced inputs and true differential inputs as well as signals
with some arbitrary reference voltage.
A particular input configuration is assigned during the MUX
addressing sequence, prior to the start of a conversion. The
MUX address selects which of the analog inputs are to be