2 8-Channel, I C, 12-Bit SAR ADC with Temperature Sensor Data Sheet AD7291 FEATURES FUNCTIONAL BLOCK DIAGRAM V DD GND 12-bit SAR ADC 8 single-ended analog input channels V Analog input range: 0 V to 2.5 V REF 12-bit temperature-to-digital converter REF BUF Temperature sensor accuracy of 1C typical 12-BIT Channel sequencer operation V IN0 SUCCESSIVE T/H Specified for V of 2.8 V to 3.6 V APPROXIMATION DD ADC Logic voltage V = 1.65 V to 3.6 V DRIVE INPUT Internal 2.5 V reference AD7291 V MUX IN7 2 I C-compatible serial interface supports standard and SEQUENCER fast speed modes SCL SDA CONTROL LOGIC Out of range indicator/alert function 2 I C INTERFACE AS1 Autocycle mode TEMP AS0 SENSOR Power-down current: 12 A maximum V DRIVE Temperature range: 40C to +125C ALERT PD/RST 20-lead LFCSP package Figure 1. On-chip limit registers can be programmed with high and low GENERAL DESCRIPTION limits for the conversion results an out-of-range indicator The AD7291 is a 12-bit, low power, 8-channel, successive output (ALERT) becomes active when the programmed high approximation analog-to-digital converter (ADC) with an or low limits are violated by the conversion result. This output internal temperature sensor. can be used as an interrupt. The device operates from a single 3.3 V power supply and 2 PRODUCT HIGHLIGHTS features an I C-compatible interface. The device contains a 9- channel multiplexer and a track-and-hold amplifier than can 1. Ideally suited to monitoring system variables in a variety handle frequencies up to 30 MHz. The device has an on-chip of systems including telecommunications, process control, 2.5 V reference that can be disabled to allow the use of an and industrial control. 2 external reference. 2. I C-compatible serial interface, which supports standard and fast modes. The AD7291 provides a 2-wire serial interface compatible with 3. Automatic partial power-down while not converting to 2 2 2 I C interfaces. The I C interface supports standard and fast I C maximize power efficiency. interface modes. The AD7291 normally remains in a partial 4. Channel sequencer operation. power-down state while not converting and powers up for 5. Integrated temperature sensor with 0.25C resolution. conversions. The conversion process can be controlled by a 2 6. Out of range indicator that can be software disabled or command mode where conversions occur across I C write enabled. operations or an autocycle mode selected through software control. Table 1. AD7291 and Related Products The AD7291 includes a high accuracy band gap temperature Device Resolution Interface Features 2 2 sensor, which is monitored and digitized by the 12-bit ADC to AD7291 12-bit IC 8-channel, I C, 12-bit SAR ADC with temperature sensor give a resolution of 0.25C. AD7298 12-bit SPI 8-channel, 1 MSPS, 12-bit SAR The AD7291 offers a programmable sequencer, which enables ADC with temperature sensor the selection of a preprogrammable sequence of channels for conversion. Rev. C 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 20112016 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. 08711-001AD7291 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Address Pointer Register ........................................................... 15 Functional Block Diagram .............................................................. 1 Command Register (0x00) ........................................................ 17 General Description ......................................................................... 1 Voltage Conversion Result Register (0x01) ............................ 18 Product Highlights ........................................................................... 1 TSENSE Conversion Result Register (0x02) ................................ 18 Revision History ............................................................................... 2 TSENSE Average Result Register (0x03) ...................................... 19 Specif icat ions ..................................................................................... 3 Limit Registers (0x04 to 0x1E) ................................................. 19 2 I C Timing Specifications ............................................................ 5 Hysteresis Register ..................................................................... 20 Absolute Maximum Ratings ............................................................ 6 Alert Status Register A and Alert Status Register B (0x1F and 0x20) ............................................................................................. 20 Thermal Resistance ...................................................................... 6 2 I C Interface .................................................................................... 21 ESD Caution .................................................................................. 6 Serial Bus Address Byte ............................................................. 21 Pin Configuration and Function Descriptions ............................. 7 2 General I C Timing .................................................................... 21 Typical Performance Characteristics ............................................. 8 Writing to the AD7291 .................................................................. 22 Terminology .................................................................................... 11 Writing Two Bytes of Data to a 16-Bit Register ..................... 22 Circuit Information ........................................................................ 12 Writing to Multiple Registers .................................................... 22 Converter Operation .................................................................. 12 Reading Data From the AD7291 .................................................. 23 Analog Input ............................................................................... 12 Reading Two Bytes of Data from a 16-Bit Register ............... 23 ADC Transfer Function ............................................................. 13 Modes of Operation ....................................................................... 24 Temperature Sensor Operation ................................................ 13 Command Mode ........................................................................ 24 Temperature Sensor Averaging ................................................. 13 Autocycle Mode .......................................................................... 26 VDRIVE ............................................................................................ 14 Outline Dimensions ....................................................................... 27 The Internal or External Reference .......................................... 14 Ordering Guide .......................................................................... 27 Reset ............................................................................................. 14 Internal Register Structure ............................................................ 15 REVISION HISTORY 10/2016Rev. B to Rev. C Changes to Command Mode Section .......................................... 25 10/2011Rev. A to Rev. B Changes to Table 9 .......................................................................... 16 8/2011Rev. 0 to Rev. A Changes to Temperature SensorInternal, Accuracy Parameter, Table 2 ................................................................................................ 3 1/2011Revision 0: Initial Version Rev. C Page 2 of 28