EVAL-AD7143-1EBZ Analog Devices Inc, EVAL-AD7143-1EBZ Datasheet - Page 15

• Manufacturer Part Number: EVAL-AD7143-1EBZ
• Description: BOARD EVALUATION FOR AD7143-1
• Manufacturer: Analog Devices Inc
• Type: Capacitive Touch and Proximity Sensorr

Specifications of EVAL-AD7143-1EBZ

• Contents: *
• For Use With/related Products: AD7143-1
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The number of required conversion stages depends completely
on the number of sensors attached to the AD7143. Figure 24
shows how many conversion stages are required for each sensor,
and how many inputs each sensor requires to the AD7143.
SRC
A button sensor generally requires one sequencer stage.
However, it is possible to configure two button sensors to
operate differentially for special applications where the user
should not press both buttons simultaneously, such as a with
rocker zoom switch on a digital camera.
8-ELEMENT
SLIDER
CIN0
CIN1
CIN2
CIN3
CIN4
CIN5
CIN6
CIN7
Figure 24. Sequencer Setup for Sensors
Figure 23. CDC Conversion Stages
SEQUENCER
AD7143
STAGE0
STAGE1
STAGE2
STAGE3
STAGE4
STAGE5
STAGE6
STAGE7
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
– CDC
STAGE0
CDC
CDC
CDC
CDC
CDC
CDC
CDC
STAGE1
STAGE2
STAGE3
STAGE4
STAGE5
STAGE6
16-BIT
STAGE7
ADC
Σ-Δ
SRC
BUTTONS
S1
S2
S3
SEQUENCER
AD7143
STAGE0
STAGE1
+
–
+
–
CDC
CDC
Rev. 0 | Page 15 of 56
In this case, only one button from the pair is activated at a time;
pressing both buttons together activates neither button. This
example is shown in Figure 24 for sensor buttons S2 and S3.
A scroll bar or slider requires eight stages. The result from each
stage is used by the host software to determine the user’s
position on the scroll bar. The algorithm that performs this
process is available from Analog Devices free of charge, upon
signing a software license. Scroll wheels also require eight stages.
CDC CONVERSION SEQUENCE TIME
The time required for one complete measurement for all eight
stages by the CDC is defined as the CDC conversion sequence
time. The SEQUENCE_STAGE_NUM register and
DECIMATION register determine the conversion time as listed
in Table 8.
Table 8. CDC Conversion Times for Full Power Mode
SEQUENCE_STAGE_NUM
0
1
2
3
4
5
6
7
For example, while operating with a decimation rate of 128,
if the SEQUENCE_STAGE_NUM register is set to 5 for the
conversion of six stages in a sequence, the conversion sequence
time is 9.216 ms.
Full Power Mode CDC Conversion Sequence Time
The full power mode CDC conversion sequence time for all
eight stages is set by configuring the SEQUENCE_STAGE_NUM
register and the DECIMATION register as outlined in Table 8.
Figure 25 shows a simplified timing diagram of the full power
CDC conversion time. The full power mode CDC conversion
time t
CONVERSION
CONV_FP
Figure 25. Full Power Mode CDC Conversion Sequence Time
CDC
is set using Table 8.
CONVERSION
SEQUENCE N
t
CONV_FP
Decimation = 128
1.525
3.072
4.608
6.144
7.68
9.216
10.752
12.288
SEQUENCE N + 1
CONVERSION
Conversion Time (ms)
SEQUENCE N + 2
CONVERSION
Decimation = 256
3.072
6.144
9.216
12.288
15.25
18.432
21.504
24.576
AD7143