ADC08134 National Semiconductor, ADC08134 Datasheet - Page 16

• Manufacturer Part Number: ADC08134
• Description: 8-Bit High-Speed Serial I/O A/D Converters with Multiplexer Options/ Voltage Reference/ and Track/Hold Function
• Manufacturer: National Semiconductor

www.national.com
Functional Description
Adjusting for an Arbitrary Analog Input
Voltage Range
If the analog zero voltage of the A/D is shifted away from
ground (for example, to accommodate an analog input signal
which does not go to ground), this new zero reference
should be properly adjusted first. A V
equals this desired zero reference plus
LSB is calculated for the desired analog span, using 1 LSB =
analog span/256) is applied to selected “+” input and the
zero reference voltage at the corresponding “−” input should
then be adjusted to just obtain the 00
sition.
The full-scale adjustment should be made [with the proper
V
put which is given by:
Applications
*Pinouts shown for ADC08138.
For all other products tie to pin functions as shown.
IN
(−) voltage applied] by forcing a voltage to the V
A “Stand-Alone” Hook-Up for ADC08138 Evaluation
HEX
IN
(Continued)
to 01
1
⁄
(+) voltage which
2
LSB (where the
HEX
code tran-
IN
(+) in-
16
where:
and
(Both are ground referenced.)
The V
code change from FE
justment procedure.
V
V
MAX
MIN
REF
= the low end (the offset zero) of the analog range.
= the high end of the analog input range
IN (or V
CC
) voltage is then adjusted to provide a
HEX
to FF
HEX
. This completes the ad-
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