Datasheet

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SLAS370C − APRIL 2002 − REVISED OCTOBER 2004
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14
A/D Converter
The 14-bit A/D converter in the ADS7871 is a successive approximation type. The output of the converter is
2s complement format and can be read through the serial interface MSB first or LSB first. A plot of output codes
vs input voltage is shown in Figure 16. With the input multiplexer configured for differential input, the A/D
transfer function is:
* 8192 v Code v 8191 for
* V
REF
G
v V
IN
v
V
REF
* 1LSB
G
With the input multiplexer configured for single-ended inputs, the A/D transfer function is:
0 v Code v 8191 for 0 v V
IN
v
V
REF
* 1LSB
G
–V
REF
+V
REF
10 0000 0000 0001 (–8191)
10 0000 0000 0000 (–8192)
Zero Transition
Output Code is 2s Complement
00 0000 0000 0010 (2)
00 0000 0000 0001 (1)
00 0000 0000 0000 (0)
INPUT VOLTAGE
OUTPUT CODE
Negative Full Scale Transition
Positive Full Scale Transition
01 1111 1111 1111 (8191)
01 1111 1111 1110 (8190)
11 1111 1111 1111 (–1)
11 1111 1111 1110 (–2)
Figure 16. Output Codes Versus Input Voltage
(1)
(2)