AD7153 Analog Devices, AD7153 Datasheet - Page 18

• Manufacturer Part Number: AD7153
• Description: 12-Bit Capacitance-to-Digital Converter (1 Capacitance Input Channel)
• Manufacturer: Analog Devices

Specifications of AD7153

• Resolution (bits): 12bit
• # Chan: 1
• Sample Rate: 200SPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: Capacitive
• Ain Range: ±0.25 pF to ±2 pF Diff,0.5 pF to 4 pF SE
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

AD7152/AD7153
CIRCUIT DESCRIPTION
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 I
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 parts.
CIN1(+)
CIN1(–)
CIN2(+)
CIN2(–)
CIN1(+)
CIN1(–)
EXC1
EXC2
EXC1
MUX
MUX
Figure 25. AD7152 Block Diagram
Figure 26. AD7153 Block Diagram
CAP+
CAP–
EXCITATION
CAP+
CAP–
EXCITATION
GENERATOR
GENERATOR
CLOCK
CLOCK
MODULATOR
MODULATOR
12-BIT Σ-Δ
12-BIT Σ-Δ
DIGITAL
DIGITAL
FILTER
FILTER
GND
GND
VDD
VDD
2
REFERENCE
REFERENCE
C-compatible serial
VOLTAGE
VOLTAGE
CONTROL LOGIC
CONTROL LOGIC
CALIBRATION
CALIBRATION
INTERFACE
INTERFACE
SERIAL
SERIAL
AD7152
I
AD7153
I
2
2
C
C
SDA
SCL
SDA
SCL
Rev. 0 | Page 18 of 24
CAPACITANCE-TO-DIGITAL CONVERTER (CDC)
Figure 27 shows the CDC simplified functional diagram. The
measured capacitance C
source and the Σ-Δ modulator input. A square-wave excitation
signal is applied on the C
ulator continuously samples the charge going through the C
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 C
be isolated from ground.
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.
C
X
EXC
CIN
Figure 27. CDC Simplified Block Diagram
CAPACITANCE-TO-DIGITAL CONVERTER
MODULATOR
X
GENERATOR
12-BIT Σ-Δ
EXCITATION
X
is connected between the excitation
CLOCK
during the conversion and the mod-
(CDC)
DIGITAL
FILTER
X
DATA
plates have to
X
.