Ultra-Low Power, 1-Channel, Capacitance Converter for Proximity Sensing AD7151 FEATURES GENERAL DESCRIPTION Ultra-low power The AD7151 delivers a complete signal processing solution for 2.7 V to 3.6 V, 70 A capacitive proximity sensors, featuring an ultra-low power Response time: 10 ms converter with fast response time. The AD7150 is a 2-channel Adaptive environmental compensation alternative to the AD7151. 1 capacitance input channel The AD7151 uses Analog Devices, Inc., capacitance-to-digital Sensor capacitance (C ) 0 pF up to 13 pF SENS converter (CDC) technology, which combines features Sensitivity to 1 fF important for interfacing to real sensors, such as high input EMC tested sensitivity and high tolerance of both input parasitic ground 2 modes of operation capacitance and leakage current. Standalone with fixed settings The integrated adaptive threshold algorithm compensates for Interfaced to a microcontroller for user-defined settings any variations in the sensor capacitance due to environmental Proximity detection output flag 2 factors like humidity and temperature or due to changes in the 2-wire serial interface (I C compatible) dielectric material over time. Operating temperature 40C to +85C By default, the AD7151 operates in standalone mode using the 10-lead MSOP package fixed power-up settings and indicates detection on a digital output. Alternatively, the AD7151 can be interfaced to a APPLICATIONS microcontroller via the serial interface, the internal registers can Proximity sensing be programmed with user-defined settings, and the data and Contactless switching status can be read from the part. Position detection The AD7151 operates with a 2.7 V to 3.6 V power supply. It is Level detection specified over the temperature range of 40C to +85C. FUNCTIONAL BLOCK DIAGRAM VDD AD7151 CIN SCL DIGITAL SERIAL - CDC FILTER INTERFACE C SENS SDA EXCITATION EXC THRESHOLD OUT GND Figure 1. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 07086-001AD7151 TABLE OF CONTENTS Features .............................................................................................. 1 Fixed Threshold Register........................................................... 16 Applications....................................................................................... 1 Sensitivity Register ..................................................................... 16 General Description ......................................................................... 1 Timeout Register ........................................................................ 17 Functional Block Diagram .............................................................. 1 Setup Register ............................................................................. 18 Revision History ............................................................................... 2 Configuration Register .............................................................. 19 Specifications..................................................................................... 3 Power-Down Timer Register .................................................... 20 Timing Specifications .................................................................. 4 CAPDAC Register...................................................................... 20 Absolute Maximum Ratings............................................................ 5 Serial Number Register.............................................................. 20 ESD Caution.................................................................................. 5 Chip ID Register......................................................................... 20 Pin Configuration and Function Descriptions............................. 6 Serial Interface ................................................................................ 21 Typical Performance Characteristics ............................................. 7 Read Operation........................................................................... 21 Architecture and Main Features ................................................... 10 Write Operation.......................................................................... 21 Capacitance-to-Digital Converter............................................ 10 AD7151 Reset ............................................................................. 22 CAPDAC ..................................................................................... 10 General Call ................................................................................ 22 Comparator and Threshold Modes.......................................... 11 Hardware Design Considerations ................................................ 23 Adaptive Threshold.................................................................... 11 Overview ..................................................................................... 23 Data Average ............................................................................... 11 Parasitic Capacitance to Ground.............................................. 23 Sensitivity..................................................................................... 12 Parasitic Resistance to Ground................................................. 23 Hysteresis..................................................................................... 12 Parasitic Parallel Resistance ...................................................... 23 Timeout........................................................................................ 12 Parasitic Serial Resistance ......................................................... 24 AutoCAPDAC Adjustment....................................................... 13 Input Overvoltage Protection ................................................... 24 Power-Down Timer ................................................................... 13 Input EMC Protection ............................................................... 24 Power Supply Monitor ............................................................... 13 Power Supply Decoupling and Filtering.................................. 24 Register Descriptions ..................................................................... 14 Application Examples ................................................................ 25 Status Register............................................................................. 15 Outline Dimensions....................................................................... 26 Data Register ............................................................................... 16 Ordering Guide .......................................................................... 26 Average Register ......................................................................... 16 REVISION HISTORY 11/07Revision 0: Initial Version Rev. 0 Page 2 of 28