Photometric Front End Data Sheet ADPD103 FEATURES GENERAL DESCRIPTION Multifunction photometric front end The ADPD103 is a highly efficient photometric front end with Fully integrated AFE, ADC, LED drivers, and timing core an integrated 14-bit analog-to-digital converter (ADC) and a Usable in a broad range of optical measurement 20-bit burst accumulator that works in concert with flexible applications, including photoplethysmography light emitting diode (LED) drivers. It is designed to stimulate an Enables best-in-class ambient light rejection capability LED and measure the corresponding optical return signal. The without the need for photodiode optical filters 2 data output and functional configuration occur over a 1.8 V I C Three 8 mA to 250 mA LED drivers interface. The control circuitry includes flexible LED signaling and Separate data registers for each LED/photodiode synchronous detection. combination The analog front end (AFE) features best-in-class rejection of signal 1 to 8 optical inputs Flexible, multiple, short LED pulses per optical sample offset and corruption due to modulated interference commonly 20-bit burst accumulator enabling 20 bits per sample period caused by ambient light. On-board sample to sample accumulator, enabling up to Couple the ADPD103 with a low capacitance photodiode of 27 bits per data read <100 pF for optimal performance. The ADPD103 can be used with Low power operation any LED. 2 I C interface and 1.8 V analog/digital core Flexible sampling frequency ranging from 0.122 Hz to 3.820 kHz FIFO data operation APPLICATIONS Body worn health and fitness monitors, for example, heart rate monitoring Clinical measurements, for example, SpO 2 Industrial monitoring Background light measurements Rev. B Document Feedback 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 20152016 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Technical Support www.analog.com ADPD103 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 AFE Integration Offset Adjustment ......................................... 18 2 Applications ....................................................................................... 1 I C Serial Interface ..................................................................... 20 General Description ......................................................................... 1 Typical Connection Diagram ................................................... 21 Revision History ............................................................................... 2 LED Driver Pins and LED Supply Voltage .............................. 23 Functional Block Diagram .............................................................. 3 LED Driver Operation ............................................................... 23 Specifications ..................................................................................... 4 Determining the Average Current ........................................... 23 Temperature and Power Specifications ..................................... 4 Determining C ..................................................................... 23 VLED Performance Specifications ......................................................... 5 LED Inductance Considerations .............................................. 24 Analog Specifications ................................................................... 6 Recommended Start-Up Sequence .......................................... 24 Digital Specifications ................................................................... 7 Reading Data ............................................................................... 24 Timing Specifications .................................................................. 8 Clocks and Timing Calibration ................................................ 26 Absolute Maximum Ratings ............................................................ 9 Calculating Current Consumption .......................................... 27 Thermal Resistance ...................................................................... 9 Optimizing SNR per Watt ......................................................... 27 Recommended Soldering Profile ............................................... 9 Single AFE channel mode ......................................................... 28 ESD Caution .................................................................................. 9 TIA ADC Mode ......................................................................... 28 Pin Configurations and Function Descriptions ......................... 10 Digital Integrate Mode............................................................... 30 Typical Performance Characteristics ........................................... 12 Register Listing ............................................................................... 34 Theory of Operation ...................................................................... 13 LED Control Registers ............................................................... 38 Introduction ................................................................................ 13 AFE Configuration Registers .................................................... 41 Dual Time Slot Operation ......................................................... 13 System Registers ......................................................................... 46 Time Slot Switch ......................................................................... 14 ADC Registers ............................................................................ 50 Adjustable Sampling Frequency ............................................... 15 Data Registers ............................................................................. 51 State Machine Operation ........................................................... 16 Outline Dimensions ....................................................................... 52 Normal Mode Operation and Data Flow ................................ 16 Ordering Guide .......................................................................... 52 AFE Operation ............................................................................ 18 REVISION HISTORY 2/16Revision B: Initial Version Rev. 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