AD7156 Datasheet, PDF (1/28 Pages) Analog Devices – Ultralow Power, 1.8 V, 3 mm × 3 mm, 2-Channel Capacitance Converter

Ultralow Power, 1.8 V, 3 mm × 3 mm,
2-Channel Capacitance Converter
AD7156
FEATURES
Ultralow power
Power supply voltage: 1.8 V to 3.6 V
Operation power supply current: 70 μA typical
Power-down current: 2 μA typical
Fast response time
Conversion time: 10 ms per channel
Wake-up time from serial interface: 300 μs
Adaptive environmental compensation
2 capacitance input channels
Sensor capacitance (CSENS): 0 pF up to 13 pF
Sensitivity up to 3 fF
2 modes of operation
Standalone with fixed settings
Interfaced to a microcontroller for user-defined settings
2 detection output flags
2-wire serial interface (I²C-compatible)
Operating temperature: −40°C to +85°C
10-lead LFCSP package (3 mm × 3 mm × 0.8 mm)
APPLICATIONS
Buttons and switches
Proximity sensing
Contactless switching
Position detection
Level detection
Portable products
GENERAL DESCRIPTION
The AD7156 delivers a complete signal processing solution for
capacitive sensors, featuring an ultralow power converter with
fast response time.
The AD7156 uses an Analog Devices, Inc., capacitance-to-
digital converter (CDC) technology, which combines features
important for interfacing to real sensors, such as high input
sensitivity and high tolerance of both input parasitic ground
capacitance and leakage current.
The integrated adaptive threshold algorithm compensates for
any variations in the sensor capacitance due to environmental
factors like humidity and temperature or due to changes in the
dielectric material over time.
By default, the AD7156 operates in standalone mode using the
fixed power-up settings and indicates detection on two digital
outputs. Alternatively, the AD7156 can be interfaced to a micro-
controller via the serial interface, the internal registers can be
programmed with user-defined settings, and the data and status
can be read from the part.
The AD7156 operates with a 1.8 V to 3.6 V power supply. It is
specified over the temperature range of −40°C to +85°C.
FUNCTIONAL BLOCK DIAGRAM
VDD
C_SENS1
C_SENS2
CIN1
EXC1
CIN2
EXC2
MUX
Σ-Δ CDC
AD7156
EXCITATION
DIGITAL
FILTER
THRESHOLD
THRESHOLD
SERIAL
INTERFACE
SCL
SDA
OUT1
OUT2
GND
Figure 1.
Rev. 0
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