2-Channel, 2.35 V to 5.25 V 250 kSPS, 10-/12-Bit ADCs AD7911/AD7921 FUNCTIONAL BLOCK DIAGRAM FEATURES V DD Fast throughput rate: 250 kSPS Specified for VDD of 2.35 V to 5.25 V Low power: V IN0 10-/12-BIT 4 mW typ at 250 kSPS with 3 V supplies SUCCESSIVE MUX T/H APPROXIMATION V 13.5 mW typ at 250 kSPS 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 AD7911/AD7921 CONTROL LOGIC SPI/QSPI/MICROWIRE/DSP compatible DOUT Standby mode: 1 A maximum DIN 8-lead TSOT package 8-lead MSOP package GND APPLICATIONS Figure 1. Battery-powered systems: Personal digital assistants The AD7911/AD7921 use advanced design techniques to Medical instruments achieve very low power dissipation at high throughput rates. Mobile communications Instrumentation and control systems The reference for the part is taken internally from V , thereby DD Data acquisition systems allowing the widest dynamic input range to the ADC. The High speed modems analog input range for the part, therefore, is 0 to VDD. The Optical sensors conversion rate is determined by the SCLK signal. GENERAL DESCRIPTION PRODUCT HIGHLIGHTS 1 1. 2-channel, 250 kSPS, 10-/12-bit ADCs in TSOT package. The AD7911/AD7921 are 10-bit and 12-bit, high speed, low 2. Low power consumption. power, 2-channel successive approximation ADCs, respectively. 3. Flexible power/serial clock speed management. The parts operate from a single 2.35 V to 5.25 V power supply The conversion rate is determined by the serial clock and feature throughput rates of up to 250 kSPS. The parts conversion time is reduced when the serial clock speed is contain a low noise, wide bandwidth track-and-hold amplifier, increased. The parts also feature a power-down mode to which can handle input frequencies in excess of 6 MHz. The maximize power efficiency at lower throughput rates. conversion process and data acquisition are controlled using CS Average power consumption is reduced when the power- and the serial clock, allowing the devices to interface with down mode is used while not converting. Current microprocessors or DSPs. The input signal is sampled on the consumption is 1 A maximum and 50 nA typically when falling edge of CS, and the conversion is also initiated at this in power-down mode. point. There are no pipeline delays associated with the part. 4. Reference derived from the power supply. 5. No pipeline delay. The channel to be converted is selected through the DIN pin, The parts feature a standard successive approximation CS and the mode of operation is controlled by . The serial data CS ADC with accurate control of the sampling instant via a stream from the DOUT pin has a channel identifier bit, which input and once-off conversion control. provides information about the converted channel. 1 Protected by U.S. Patent Number 6,681,332. Rev. A 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 20042011 Analog Devices, Inc. All rights reserved. 04350-0-001AD7911/AD7921 TABLE OF CONTENTS Specifications..................................................................................... 3 Analog Input ............................................................................... 16 AD7911 Specifications................................................................. 3 Digital Inputs .............................................................................. 17 AD7921 Specifications................................................................. 5 DIN Input.................................................................................... 17 Timing Specifications .................................................................. 7 DOUT Output ............................................................................ 17 Timing Diagrams.......................................................................... 7 Modes of Operation ....................................................................... 18 Timing Examples.......................................................................... 8 Normal Mode.............................................................................. 18 Absolute Maximum Ratings............................................................ 9 Power-Down Mode.................................................................... 18 ESD Caution.................................................................................. 9 Power-Up Time .......................................................................... 19 Pin Configurations and Function Descriptions ......................... 10 Power vs. Throughput Rate....................................................... 20 Terminology .................................................................................... 11 Serial Interface ................................................................................ 21 Typical Performance Characteristics ........................................... 13 Microprocessor Interfacing....................................................... 22 Circuit Information........................................................................ 15 Application Hints ........................................................................... 24 Converter Operation.................................................................. 15 Grounding and Layout .............................................................. 24 ADC Transfer Function............................................................. 15 Outline Dimensions ....................................................................... 25 Typical Connection Diagram ................................................... 16 Ordering Guide .......................................................................... 25 REVISION HISTORY 5/11Rev. 0 to Rev. A Updated Outline Dimensions ....................................................... 25 Changes to Ordering Guide .......................................................... 25 4/04Revision 0: Initial Version Rev. A Page 2 of 28