MAX1400_02 Datasheet, PDF (20/34 Pages) Maxim Integrated Products – +5V, 18-Bit, Low-Power, Multichannel, Oversampling (Sigma-Delta) ADC

+5V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
Table 11. Channel ID Tag Codes
CID2
0
0
0
0
1
1
1
1
CID1
0
0
1
1
0
0
1
1
CID0
0
1
0
1
0
1
0
1
CHANNEL
AIN1–AIN6
AIN2–AIN6
AIN3–AIN6
AIN4–AIN6
AIN1–AIN2
AIN3–AIN4
AIN5–AIN6
Calibration
Switching Network
A switching network provides selection between three
fully differential input channels or five pseudo-differen-
tial channels, using AIN6 as a shared common. The
switching network provides two additional fully differen-
tial input channels intended for system calibration,
which may be used as extra fully differential signal
channels. Table 12 shows the channel configurations
available for both operating modes.
Scanning (SCAN-mode)
To sample and convert the available input channels
sequentially, set the SCAN control bit in the global
setup register. The sequence is determined by DIFF
(fully differential or pseudo-differential) and by the
mode control bits M1 and M0 (Tables 8, 9, 10). With
SCAN set, the part automatically sequences through
each available channel, transmitting a single conver-
sion result before proceeding to the next channel. The
MAX1400 automatically allows sufficient time for each
conversion to fully settle, to ensure optimum resolution
before asserting the data-ready signal and moving to
the next available channel. The scan rate is, therefore,
dependent on the clock bit (CLK), the filter control bits
(FS1, FS0), and the modulator frequency selection bits
(MF1, MF0).
Burnout Currents
The input circuitry also provides two “burnout” currents.
These small currents may be used to test the integrity
of the selected transducer. They can be selectively
enabled or disabled by the BOUT bit in the global
setup register.
Table 12. Input Channel Configuration in Fully and Pseudo-Differential Modes
(SCAN = 0)
M1
M0
DIFF
A1
A0
MODE
HIGH INPUT
0
0
0
0
0
AIN1
0
0
0
0
1
AIN2
0
0
0
1
0
0
0
0
1
1
Pseudo-
Differential
0
0
X
X
X
AIN3
AIN4
AIN5*
0
1
X
X
X
CALOFF+**
1
0
X
X
X
CALGAIN+**
0
0
1
0
0
AIN1
0
0
1
0
1
AIN3
0
0
1
1
0
Fully
Differential
AIN5
0
1
X
X
X
CALOFF+**
1
0
X
X
X
CALGAIN+**
X = Don’t Care.
* This combination is available only in pseudo-differential mode when using the internal scanning logic
** These combinations are only available in the calibration modes.
LOW INPUT
AIN6
AIN6
AIN6
AIN6
AIN6*
CALOFF-**
CALGAIN-**
AIN2
AIN4
AIN6
CALOFF-**
CALGAIN-**
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