8-Channel, 1 MSPS, 12-Bit SAR ADC with Temperature Sensor AD7298 FEATURES FUNCTIONAL BLOCK DIAGRAM V DD GND 12-bit SAR ADC 8 single-ended inputs V Channel sequencer functionality REF Fast throughput of 1 MSPS REF BUF Analog input range: 0 V to 2.5 V 12-bit temperature-to-digital converter 12-BIT V IN0 SUCCESSIVE T/H Temperature sensor accuracy of 1C APPROXIMATION ADC Temperature range: 40C to +125C INPUT Specified for V : 2.8 V to 3.6 V DD AD7298 V MUX IN7 Logic voltage VDRIVE : 1.65 V to 3.6 V Power-down current: <10 A SEQUENCER SCLK Internal 2.5 V reference DOUT CONTROL DIN Internal power-on reset LOGIC TEMP CS SENSOR High speed serial interface SPI V DRIVE 20-lead LFCSP T BUSY PD/RST SENSE Figure 1. PRODUCT HIGHLIGHTS GENERAL DESCRIPTION 1. Ideally Suited to Monitoring System Variables in a Variety The AD7298 is a 12-bit, high speed, low power, 8-channel, of Systems. This includes telecommunications, and process successive approximation ADC with an internal temperature and industrial control. sensor. The part operates from a single 3.3 V power supply and features throughput rates up to 1 MSPS. The device contains a 2. High Throughput Rate of 1 MSPS with Low Power low noise, wide bandwidth track-and-hold amplifier that can Consumption. handle input frequencies in excess of 30 MHz. 3. Eight Single-Ended Inputs with a Channel Sequencer. The AD7298 offers a programmable sequencer, which enables A consecutive sequence of channels can be selected on the selection of a preprogrammable sequence of channels for which the ADC cycles and converts. conversion. The device has an on-chip, 2.5 V reference that can 4. Integrated Temperature Sensor with 0.25C Resolution. be disabled to allow the use of an external reference. The AD7298 includes a high accuracy band gap temperature sensor, which is monitored and digitized by the 12-bit ADC to give a resolution of 0.25C. The device offers a 4-wire serial interface compatible with SPI and DSP interface standards. The AD7298 uses advanced design techniques to achieve very low power dissipation at high throughput rates. The part also offers flexible power/throughput rate management options. The part is offered in a 20-lead LFCSP package. Rev. B 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. 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Trademarks and registered trademarks are the property of their respective owners. 08754-001AD7298 TABLE OF CONTENTS Features .............................................................................................. 1 Temperature Sensor Averaging ................................................ 14 General Description ......................................................................... 1 VDRIVE............................................................................................ 15 Functional Block Diagram .............................................................. 1 The Internal or External Reference.......................................... 15 Product Highlights ........................................................................... 1 Control Register.............................................................................. 16 Revision History ............................................................................... 2 Modes of Operation ....................................................................... 17 Specifications..................................................................................... 3 Traditional Multichannel Mode of Operation........................ 17 Timing Specifications .................................................................. 5 Repeat Operation ....................................................................... 18 Absolute Maximum Ratings............................................................ 6 Power-Down Modes .................................................................. 19 ESD Caution.................................................................................. 6 Powering Up the AD7298 ......................................................... 20 Thermal Resistance ...................................................................... 6 Reset ............................................................................................. 20 Pin Configuration and Function Description .............................. 7 Serial Interface ................................................................................ 21 Typical Performance Characteristics ............................................. 9 Temperature Sensor Read ......................................................... 22 Terminology .................................................................................... 12 Layout and Configuration............................................................. 23 Circuit Information........................................................................ 13 Power Supply Bypassing and Grounding................................ 23 Converter Operation.................................................................. 13 Temperature Monitoring........................................................... 23 Analog Input ............................................................................... 13 Outline Dimensions....................................................................... 24 Temperature Sensor Operation ................................................ 14 Ordering Guide .......................................................................... 24 REVISION HISTORY 6/11Rev. A to Rev. B Changes to Internal Temperature Sensor, Accuracy Parameter in Table 1............................................................................................ 3 1/11Rev. 0 to Rev. A Removed Input Impedance Parameter .......................................... 3 Added Input Capacitance Parameter of 8 pF................................ 3 Changes to Figure 11...................................................................... 10 Changed C1 Value to 8 pF in Analog Input Section.................. 13 Changes to Figure 23...................................................................... 14 Changes to Ordering Guide .......................................................... 24 9/10Revision 0: Initial Version Rev. B Page 2 of 24