8-Channel, 625 kSPS, 12-Bit Parallel ADCs with a Sequencer Data Sheet AD7938-6 FEATURES FUNCTIONAL BLOCK DIAGRAM V AGND DD Throughput rate: 625 kSPS Specified for V of 2.7 V to 5.25 V DD AD7938-6 V / REFIN V REFOUT Power consumption 2.5V 3.6 mW maximum at 625 kSPS with 3 V supplies V REF V 0 IN 7.5 mW maximum at 625 kSPS with 5 V supplies CLKIN 12-BIT SAR ADC 8 analog input channels with a sequencer I/P CONVST T/H AND MUX CONTROL Software-configurable analog inputs BUSY V 7 IN 8-channel single-ended inputs 4-channel fully differential inputs 4-channel pseudo differential inputs SEQUENCER 7-channel pseudo differential inputs Accurate on-chip 2.5 V reference PARALLEL INTERFACE/CONTROL REGISTER V DRIVE 0.2% maximum at 25C, 25 ppm/C maximum 69 dB SINAD at 50 kHz input frequency No pipeline delays DB0 DB11 CS RD WR W/B DGND High speed parallel interface with word/byte modes Full shutdown mode: 2 A maximum Figure 1. 32-lead LFCSP and TQFP packages GENERAL DESCRIPTION control register allows the user to set up different operating The AD7938-6 is a 12-bit, high speed, low power, successive conditions, including analog input range and configuration, approximation (SAR) analog-to-digital converter (ADC). The output coding, power management, and channel sequencing. part operates from a single 2.7 V to 5.25 V power supply and features throughput rates up to 625 kSPS. The part contains a PRODUCT HIGHLIGHTS low noise, wide bandwidth, differential track-and-hold 1. High throughput with low power consumption. amplifier that can handle input frequencies up to 50 MHz. 2. Eight analog inputs with a channel sequencer. The AD7938-6 features eight analog input channels with a 3. Accurate on-chip 2.5 V reference. channel sequencer that allows a preprogrammed selection of 4. Single-ended, pseudo differential, or fully differential channels to be converted sequentially. The part can operate analog inputs that are software selectable. with either single-ended, fully differential, or pseudo differential 5. Single-supply operation with VDRIVE function. The VDRIVE analog inputs. function allows the parallel interface to connect directly to The conversion process and data acquisition are controlled 3 V or 5 V processor systems independent of VDD. using standard control inputs that allow easy interfacing with 6. No pipeline delay. CONVST microprocessors and DSPs. The input signal is sampled on the 7. Accurate control of the sampling instant via a falling edge of CONVST and the conversion is initiated at input and once-off conversion control. this point. Table 1. The AD7938-6 has an accurate on-chip 2.5 V reference that Similar Device No. of Bits No. of Channels Speed can be used as the reference source for the analog-to-digital AD7938/AD7939 12/10 8 1.5 MSPS conversion. Alternatively, this pin can be overdriven to provide AD7933/AD7934 10/12 4 1.5 MSPS an external reference. AD7934-6 12 4 625 kSPS The AD7938-6 uses advanced design techniques to achieve very low power dissipation at high throughput rates. The part also features flexible power management options. An on-chip Rev. F 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. Tel: 781.329.4700 20042020 Analog Devices, Inc. All rights reserved. No license is granted by implication or otherwise under any patent or patent rights of Analog Technical Support www.analog.com Devices. Trademarks and registered trademarks are the property of their respective owners. 04751-001AD7938-6 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 ADC Transfer Function ............................................................ 16 Functional Block Diagram .............................................................. 1 Typical Connection Diagram ................................................... 17 General Description ......................................................................... 1 Analog Input Structure ............................................................. 17 Product Highlights ....................................................................... 1 Analog Inputs ............................................................................. 18 Revision History ............................................................................... 2 Analog Input Selection .............................................................. 20 Specifications .................................................................................... 3 Reference ..................................................................................... 21 Timing Specifications .................................................................. 5 Parallel Interface ......................................................................... 23 Absolute Maximum Ratings ........................................................... 6 Power Modes of Operation ....................................................... 26 ESD Caution.................................................................................. 6 Power vs. Throughput Rate ...................................................... 27 Pin Configurations and Function Descriptions ........................... 7 Microprocessor Interfacing ...................................................... 27 Typical Performance Characteristics ............................................. 9 Application Hints ........................................................................... 29 Terminology .................................................................................... 11 Grounding and Layout .............................................................. 29 On-Chip Registers .......................................................................... 13 PCB Design Guidelines for Chip Scale Package .................... 29 Control Register ......................................................................... 13 Evaluating the AD7938-6 Performance .................................. 29 Sequencer Operation ................................................................. 14 Outline Dimensions ....................................................................... 30 Shadow Register ......................................................................... 14 Ordering Guide .......................................................................... 30 Circuit Information ........................................................................ 16 Converter Operation .................................................................. 16 REVISION HISTORY 10/2011Rev. B to Rev. C 11/2020Rev. E to Rev. F Change to Features Section .............................................................. 1 Changed CP-32-2 to CP-32-7 ...................................... Throughout Updated Outline Dimensions ....................................................... 30 10/2011Rev. A to Rev. B Changes to Ordering Guide .......................................................... 30 Changes to Table 2 ............................................................................ 3 Changes to Figure 2 and Table 5 ..................................................... 7 4/2018Rev. D to Rev. E Added Exposed Pad Notation to Outline Dimensions ............. 30 Updated Outline Dimensions ....................................................... 30 Changes to Ordering Guide .......................................................... 31 Changes to Ordering Guide .......................................................... 30 2/2007Rev. 0 to Rev. A 1/2017Rev. C to Rev. D Changes to Specifications ................................................................. 3 Changed CP-32-2 to CP-32-7 ...................................... Throughout Changes to Figure 13 ..................................................................... 10 Changes to Figure 2 .......................................................................... 7 Changes to Sequencer Operation Section ................................... 14 Added Figure 3 Renumbered Sequentially .................................. 7 Changes to Analog Inputs Section ............................................... 18 Updated Outline Dimensions ....................................................... 30 Updated Outline Dimensions ...................................................... 30 Changes to Ordering Guide .......................................................... 31 10/2004Revision 0: Initial Version Rev. F Page 2 of 30