AD7142 Analog Devices, AD7142 Datasheet - Page 19

• Manufacturer Part Number: AD7142
• Description: Programmable Controller for Capacitance Touch Sensors
• Manufacturer: Analog Devices

Specifications of AD7142

• Resolution (bits): 16bit
• # Chan: 14
• Sample Rate: 250kSPS
• Interface: I²C/Ser 2-Wire,Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: ± 2 pF (Delta C)
• Adc Architecture: Sigma-Delta
• Pkg Type: CSP

CDC CONVERSION SEQUENCE
RECALIBRATION COUNTER
PROXIMITY DETECTION
CDC CONVERSION SEQUENCE
CDC CONVERSION SEQUENCE
Figure 30. Full Power Mode Proximity Detection with Forced Recalibration Example with FP_PROXIMITY_CNT = 1 and FP_PROXIMITY_RECAL = 40
PROXIMITY DETECTION
CALIBRATION
PROXIMITY DETECTION
(INTERNAL)
(INTERNAL)
(INTERNAL)
(INTERNAL)
CALIBRATION
CALIBRATION
(INTERNAL)
(INTERNAL)
(INTERNAL)
(INTERNAL)
(INTERNAL)
(INTERNAL)
NOTES
1. SEQUENCE CONVERSION TIME
2.
3.
4.
t
t
t
CALDIS
RECAL_TIMEOUT
RECAL
USER APPROACHES
SENSOR HERE
NOTES
1. SEQUENCE CONVERSION TIME
2. PROXIMITY IS SET WHEN USER APPROACHES THE SENSOR AT WHICH TIME THE INTERNAL CALIBRATION IS DISABLED.
3.
= 2 ×
=
t
Figure 28. Full Power Mode Proximity Detection Example with FP_PROXIMITY_CNT = 1
CALDIS
t
CONV_FP
t
USER APPROACHES
CONV_FP
Figure 29. Low Power Mode Proximity Detection with LP_PROXIMITY_CNT = 4
SENSOR HERE
APPROACHES
SENSOR HERE
= (
=
t
CONV_FP
t
× FP_PROXIMITY_CNT ×16
USER
CONV_LP
USER LEAVES SENSOR
CALIBRATION DISABLED
1 2 3 4 5 6 7 8 9 10 11 1213 14 15 16
1 2 3 4 5 6 7 8 9 10 11 1213 14 15 16
AREA HERE
× FP_PROXIMITY_RECAL
× LP_PROXIMITY_CNT × 4)
t
CONV_FP
16
USER LEAVES
t
USER LEAVES SENSOR
CALDIS
AREA HERE
DETERMINED FROM TABLE 10
t
SENSOR
CONV_LP
CALIBRATION DISABLED
Rev. A | Page 19 of 72
AREA HERE
CALIBRATION DISABLED
=
t
CONV_FP
30
MEASURED CDC VALUE > STORED AMBIENT
+ LP_CONV_DELAY
BY PROXIMITY_RECAL _LVL
RECALIBRATION TIME-OUT
t
CALDIS
t
CALDIS
1718 19 20 21 22 23 24
t
RECAL_TIMEOUT
CALIBRATION ENABLED
CALIBRATION ENABLED
t
RECAL
70
CALIBRATION ENABLED
t
CONV_LP
t
CONV_FP
AD7142
t
CONV_FP