AD7152/AD7153 Data Sheet
Rev. A | Page 22 of 24
The offset register of the AD7152/AD7153 allows for offset
calibration over the full capacitive input range. However, the
user must ensure that the offset to be removed is within 40% of
the full scale range; this can be achieved by using the CAPCAC
to perform a coarse offset calibration and use the system offset
calibration then to compensate for an offset within the 40% of
full-scale range pF of the CAPDAC.
The offset calibration register is reloaded by the default value
0x8000 at power-on or after reset. Therefore, if the offset
calibration is not repeated after each system power-up, the
calibration coefficient value should be stored by the host
controller and reloaded as part of the AD7152/AD7153 setup.
Note that the AD7152/AD7153 zero scale for differential mode
is around 0x8000; therefore, the offset register also needs a
value of around 0x8000, where the zero scale in single-ended
mode is 0x0000, with a required offset register value of 0x3000.
For more detailed information, see the Data Registers section.
TYPICAL APPLICATION DIAGRAM
SCL
VDD
GND
AD7153
SDA
3.3V
V
SUPPLY
1kΩ1kΩ
1kΩ
0.1µF
10µF 1µF 1µF
CIN1(+)
C
SENS1
C
SENS2
CIN1(–)
EXC1
C1
R1
C2
R2
C3
R3
C4
R4
47pF
10kΩ
ADP1720-3.3
HOST
SYSTEM
GND
07450-061
Figure 41. Basic Application Diagram for a Differential Capacitive Sensor
