Low Power, Buffered 24-Bit Sigma-Delta ADC Data Sheet AD7791 FUNCTIONAL BLOCK DIAGRAM FEATURES Power GND V REFIN(+) REFIN() DD Supply: 2.5 V to 5.25 V operation Normal: 75 A max V DD CLOCK Power-down: 1 A max RMS noise: 1.1 V at 9.5 Hz update rate AIN(+) DOUT/RDY - 19.5-bit p-p resolution (22 bits effective resolution) BUF ADC DIN AIN() SERIAL Integral nonlinearity: 3.5 ppm typical INTERFACE SCLK Simultaneous 50 Hz and 60 Hz rejection CS AD7791 GND Internal clock oscillator 04227-0-001 Rail-to-rail input buffer Figure 1. VDD monitor channel Temperature range: 40C to +105C 10-lead MSOP GENERAL DESCRIPTION The AD7791 is a low power, complete analog front end for INTERFACE low frequency measurement applications. It contains a low 3-wire serial noise 24-bit - ADC with one differential input that can be SPI, QSPI, MICROWIRE, and DSP compatible buffered or unbuffered. Schmitt trigger on SCLK The device operates from an internal clock. Therefore, the user APPLICATIONS does not have to supply a clock source to the device. The output Smart transmitters data rate from the part is software programmable and can be Battery applications varied from 9.5 Hz to 120 Hz, with the rms noise equal to Portable instrumentation 1.1 V at the lower update rate. The internal clock frequency Sensor measurement can be divided by a factor of 2, 4, or 8, which leads to a reduc- Temperature measurement tion in the current consumption. The update rate, cutoff fre- frequency, and settling time will scale with the clock frequency. Pressure measurement Weigh scales The part operates with a power supply from 2.5 V to 5.25 V. 4 to 20 mA loops When operating from a 3 V supply, the power dissipation for the part is 225 W maximum. It is housed in a 10-lead MSOP. Rev. A Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no re- sponsibility 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 20042013 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. AD7791 Data Sheet TABLE OF CONTENTS AD7791Specifications .................................................................. 3 Noise Performance ..................................................................... 14 , Timing Characteristics ................................................................... 5 Reduced Current Modes ........................................................... 14 Absolute Maximum Ratings ............................................................ 7 Digital Interface .......................................................................... 15 ESD Caution .................................................................................. 7 Single Conversion Mode ....................................................... 16 Pin Configuration and Function Descriptions ............................. 8 Continuous Conversion Mode ............................................. 16 Typical Performance Characteristics ............................................. 9 Continuous Read Mode ........................................................ 17 On-chip Registers ........................................................................... 10 Circuit Description......................................................................... 18 Communications Register (RS1, RS0 = 0, 0) .......................... 10 Analog Input Channel ............................................................... 18 Status Register (RS1, RS0 = 0, 0 Bipolar/Unipolar Configuration .............................................. 18 Power-on/Reset = 0x8C) ........................................................... 11 Data Output Coding .................................................................. 18 Mode Register (RS1, RS0 = 0, 1 Reference Input ........................................................................... 18 Power-on/Reset = 0x02) ............................................................ 11 V Monitor ................................................................................ 19 DD Filter Register (RS1, RS0 = 1, 0 Power-on/Reset = 0x04) ............................................................ 12 Grounding and Layout .............................................................. 19 Data Register (RS1, RS0 = 1, 1 Outline Dimensions ....................................................................... 20 Power-on/Reset = 0x000000) .................................................... 13 Ordering Guide .......................................................................... 20 ADC Circuit Information .............................................................. 14 Overview ...................................................................................... 14 REVISION HISTORY 3/13Rev. 0 to Rev. A Moved ESD Caution Section ............................................................ 7 Changes to Figure 13 ....................................................................... 15 Changes to Reference Input Section ............................................. 18 Updated Outline Dimensions ........................................................ 20 Changes to Ordering Guide ........................................................... 20 8/03Revision 0: Initial Version Rev. A Page 2 of 20