Switches
2-10
Since the switches for both the negative and positive inputs for each channel
have the same configuration, it is easy to set up the inputs for a variety of
applications. Some examples are given in Table 2−5.
Table 2−5. Common Input Switch Settings
Setting
Number
S1/3
(INP)
S2/4
(INN)
Setting
Ideal Voltage Range
for VRP = 2.5V
Ideal Output Code Range
(Hex 2s complement)
1
EXT
EXT
External Differential
−5V
≤
(INP − INN)
≤
5V
0x800000 < code
< 0x7FFFFF
2
EXT
0V
Single-ended,
ground-referenced
0
≤
INP
≤
5V
0x000000 < code
< 0x7FFFFF
3
EXT
VRP
Single-ended,
midscale-referenced
0
≤
INP
≤
5V
0xC00000 < code
< 0x3FFFFF
4
0V
0V
Inputs shorted to
ground
N/A
N/A (near zero)
5
VRP
VRP
Inputs shorted to
midscale
N/A
N/A (near zero)
To measure external differential signals, use Setting 1. To measure external
0V−5V signals, use either Setting 2 or 3. Note that for single-ended signals,
approximately one bit is lost from full-scale. Note that Setting 3 may provide
better headroom against full-scale clipping.
Settings 4 and 5 are useful for noise tests. When using the buffer, more accu-
rate results may be obtained with Setting 5. Also, internal offset calibration on
the ADS1224 is performed as the device is in Setting 5.
Summary of Contents for ADS1224EVM
Page 1: ... April 2004 User s Guide SBAU095 Data Acquisition Products ...
Page 14: ...Setting Up 1 6 ...
Page 30: ...Clock Circuitry 3 4 ...
