CN-0274 Datasheet, PDF (1/6 Pages) Analog Devices – Ultralow Power, 3-Axis, Motion Activated Switch

Circuit Note
CN-0274
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0274.
Devices Connected/Referenced
ADXL362
Nanopower, 3-Axis, ±2 g, ±4 g, and ±8 g
Digital Output MEMS Accelerometer
ADP195
Logic Controlled, High-Side Power Switch
with Reverse Current Blocking
Ultralow Power, 3-Axis, Motion Activated Switch
EVALUATION AND DESIGN SUPPORT
Circuit Evaluation Boards
CN-0274 Circuit Evaluation Board (EVAL-CN0274-SDPZ)
System Demonstration Platform (EVAL-SDP-CS1Z)
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
The combination of parts shown in Figure 1 provides an ultralow
power, 3-axis, motion activated power switch solution capable of
controlling up to 1.1 A of load current. The circuit is ideal for
applications where extended battery life is critical. When the switch is
off, the battery current is less than 300 nA, and when the switch is on,
it draws less than 3 µA. The circuit provides an industry leading,
low power motion sensing solution suitable for wireless sensors,
metering devices, home healthcare, and other portable applications.
The 3-axis accelerometer controls the high-side switch by
monitoring the acceleration in three axes and closes or opens
the switch depending on the presence or absence of motion.
3.3V
C_S
The ADXL362 is an ultralow power, 3-axis accelerometer
that consumes less than 100 nA in wake-up mode. Unlike
accelerometers that use power duty cycling to achieve low power
consumption, the ADXL362 does not alias input signals by under
sampling; it samples continuously at all data rates. There is also
an on-chip, 12-bit temperature sensor accurate to ±0.5°.
The ADXL362 provides 12-bit output resolution and has three
operating ranges, ±2 g, ±4 g, and ±8 g. It is specified over a
minimum temperature range of −40°C to +85°C. For applications
where a noise level less than 480 µg/√Hz is desired, either of its
two lower noise modes (down to 120 µg/√Hz) can be selected at
a minimal increase in supply current.
The ADP195 is a high-side load switch designed for operation
between 1.1 V and 3.6 V and is protected against reverse current
flow from output to input. The device contains a low on-resistance,
P-channel MOSFET that supports over 1.1 A of continuous load
current and minimizes power losses.
3.3V
C_IO
INTERRUPT
CONTROL
AWAKE
V_S
V_{DD I/O}
INT1
INT2
ADXL362
MOSI
MISO
SCLK
GND
CS
SPI
INTERFACE
VIN
VS
GND
ADP195
REVERSE
POLARITY
PROTECTION
VOUT
EN
LEVEL SHIFT
LOAD
AND SLEW
RATE CONTROL
Figure 1. Ultralow Power Standalone Motion Switch (Simplified Schematic: Decoupling and All Connections Not Shown)
Rev. A
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