2-Channel, 2.35 V to 5.25 V, 1 MSPS, 10-/12-Bit ADCs AD7912/AD7922 FUNCTIONAL BLOCK DIAGRAM FEATURES V DD Fast throughput rate: 1 MSPS Specified for VDD of 2.35 V to 5.25 V Low power: V IN0 10-/12-BIT 4.8 mW typ at 1 MSPS with 3 V supplies SUCCESSIVE MUX T/H APPROXIMATION V 15.5mW typ at 1 MSPS with 5 V supplies IN1 ADC Wide input bandwidth: 71 dB minimum SNR at 100 kHz input frequency Flexible power/serial clock speed management SCLK No pipeline delays High speed serial interface: CS AD7912/AD7922 CONTROL LOGIC SPI/QSPI/MICROWIRE/DSP compatible DOUT Standby mode: 1 A maximum DIN Daisy-chain mode 8-lead TSOT package GND 8-lead MSOP package Figure 1. APPLICATIONS Several AD7912/AD7922 can be connected together in a daisy Battery-powered systems: chain. The AD7912/AD7922 feature a daisy-chain mode that Personal digital assistants allows the user to read the conversion results from the ADCs Medical instruments contained in the chain. The AD7912/AD7922 use advanced Mobile communications design techniques to achieve very low power dissipation at high Instrumentation and control systems throughput rates. The reference for the part is taken internally Data acquisition systems from VDD, thereby allowing the widest dynamic input range to High speed modems the ADC. Optical sensors PRODUCT HIGHLIGHTS GENERAL DESCRIPTION 1. 2-channel, 1 MSPS, 10-/12-bit ADCs in TSOT package. 1 2. High throughput with low power consumption. The AD7912/AD7922 are 10-bit and 12-bit, high speed, low 3. Flexible power/serial clock speed management. power, 2-channel successive approximation ADCs, respectively. The conversion rate is determined by the serial clock. The The parts operate from a single 2.35 V to 5.25 V power supply parts also feature a power-down mode to maximize power and feature throughput rates of up to 1 MSPS. The parts contain efficiency at lower throughput rates. Average power a low noise, wide bandwidth track-and-hold amplifier, which consumption is reduced when the power-down mode is can handle input frequencies in excess of 6 MHz. used while not converting. Current consumption is 1 A The conversion process and data acquisition are controlled maximum and 50 nA typically when in power-down mode. using CS and the serial clock, allowing the devices to interface 4. Daisy-chain mode. with microprocessors or DSPs. The conversion rate is 5. No pipeline delay. determined by the SCLK signal. The input signal is sampled on The parts feature a standard successive approximation ADC CS the falling edge of and the conversion is also initiated at this CS with accurate control of the sampling instant via a input point. The channel to be converted is selected through the DIN and once-off conversion control. pin, and the mode of operation is controlled by CS. The serial data stream from the DOUT pin has a channel identifier bit and mode identifier bit, which provide information about the 1 Protected by U.S. Patent Number 6,681,332. converted channel and the current mode of operation. 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 rights of third parties that may result from its use. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Specifications subject to change without notice. No license is granted by implication Tel: 781.329.4700 www.analog.com or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Fax: 781.326.8703 2004 Analog Devices, Inc. All rights reserved. 04351-0-001AD7912/AD7922 TABLE OF CONTENTS Specifications..................................................................................... 3 DIN Input.................................................................................... 17 AD7912 Specifications................................................................. 3 DOUT Output ............................................................................ 17 AD7922 Specifications................................................................. 5 Modes of Operation ....................................................................... 18 Timing Specifications .................................................................. 7 Normal Mode.............................................................................. 18 Timing Diagrams.......................................................................... 7 Power-Down Mode.................................................................... 18 Timing Examples.......................................................................... 8 Power-Up Time .......................................................................... 20 Absolute Maximum Ratings............................................................ 9 Daisy-Chain Mode..................................................................... 20 ESD Caution.................................................................................. 9 Daisy-Chain Example................................................................ 22 Pin Configurations and Function Descriptions ......................... 10 Power vs. Throughput Rate ........................................................... 24 Terminology .................................................................................... 11 Serial Interface ................................................................................ 25 Typical Performance Characteristics ........................................... 13 Microprocessor Interfacing....................................................... 26 Circuit Information........................................................................ 15 Application Hints ........................................................................... 28 Converter Operation.................................................................. 15 Grounding and Layout .............................................................. 28 ADC Transfer Function............................................................. 15 Evaluating AD7912/AD7922 Performance................................. 29 Typical Connection Diagram ................................................... 16 Outline Dimensions ....................................................................... 30 Analog Input ............................................................................... 16 Ordering Guide .......................................................................... 30 Digital Inputs .............................................................................. 17 REVISION HISTORY Revision 0: Initial Version Rev. 0 Page 2 of 32