EVAL-AD7152EBZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-AD7152EBZ' PDF : 24 Pages View PDF
AD7152/AD7153
CIRCUIT DESCRIPTION
VDD
CIN1(+)
CIN1(–)
EXC1
CIN2(+)
CIN2(–)
EXC2
CAP+
CAP–
AD7152
CLOCK
VOLTAGE
GENERATOR REFERENCE
MUX
12-BIT Σ-∆
MODULATOR
I2C
SERIAL
INTERFACE
SDA
SCL
EXCITATION
DIGITAL
FILTER
CONTROL LOGIC
CALIBRATION
GND
Figure 25. AD7152 Block Diagram
VDD
CAP+
CAP–
AD7153
CLOCK
VOLTAGE
GENERATOR REFERENCE
CIN1(+)
CIN1(–)
EXC1
MUX
12-BIT Σ-∆
MODULATOR
I2C
SERIAL
INTERFACE
SDA
SCL
EXCITATION
DIGITAL
FILTER
CONTROL LOGIC
CALIBRATION
GND
Figure 26. AD7153 Block Diagram
The core of the AD7152/AD7153 is a precision converter
consisting of a second-order modulator (Σ-Δ or charge-
balancing) and a third-order digital filter.
In addition to the converter, the AD7152/AD7153 integrate a
multiplexer, an excitation source, and CAPDACs for the capaci-
tive inputs, a voltage reference, a complete clock generator, a
control and calibration logic, and an I2C-compatible serial
interface.
The AD7153 has one capacitive input, while the AD7152 has
two capacitive inputs. For the AD7152, the modulator input and
the excitation source are multiplexed between the converting
channel. All other features and specifications are identical for
both devices.
Data Sheet
CAPACITANCE-TO-DIGITAL CONVERTER (CDC)
Figure 27 shows the CDC simplified functional diagram. The
measured capacitance CX is connected between the excitation
source and the Σ-Δ modulator input. A square-wave excitation
signal is applied on the CX during the conversion and the mod-
ulator continuously samples the charge going through the CX.
The digital filter processes the modulator output, which is a
stream of 0s and 1s containing the information in 0 and 1
density. The data from the digital filter is scaled, applying the
calibration coefficients, and the final result can be read through
the serial interface. The AD7152/AD7153 are designed for
floating capacitive sensors. Therefore, both CX plates have to
be isolated from ground.
CAPACITANCE-TO-DIGITAL CONVERTER
(CDC)
CLOCK
GENERATOR
CIN
CX
EXC
12-BIT Σ-∆
MODULATOR
DATA
DIGITAL
FILTER
EXCITATION
Figure 27. CDC Simplified Block Diagram
EXCITATION SOURCE
The AD7152/AD7153 have one excitation source. For the
AD7152, the excitation source is switched between the
excitation pins, EXC1 and EXC2, depending on which
channel performs a conversion.
Rev. A | Page 18 of 24
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