Circuit Note

CN-0274

Circuits from the Lab™ reference circuits are engineered and

tested for quick and easysystemintegrationto helpsolve today’s

analog, mixed-signal, and RF design challenges. For more

informationand/orsupport,visitwww.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

Rev. A

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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.

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.

ADXL362

GND

INT1

INT2

CS

SCLK

MISO

MOSI

SPI

INTERFACE

3.3V

3.3V

INTERRUPT

CONTROL

AWAKE

GND

EN

VIN

VS

LOAD

VOUT

ADP195

LEVEL SHIFT

AND SLEW

RATE CONTROL

REVERSE

POLARITY

PROTECTION

Figure 1. Ultralow Power Standalone Motion Switch (Simplified Schematic: Decoupling and All Connections Not Shown)