Datasheet AD7738 (Analog Devices)

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8-Channel, High Throughput, 24-Bit - ADC AD7738 FEATURES FUNCTIONAL BLOCK DIAGRAM High Resolution ADC 24 Bits No Missing Codes MUXOUT ADCIN REFIN– REFIN+ 0.0015% Nonlinearity REFERENCE Optimized for Fast Channel Switching AIN0 DETECT 18-Bits p-p Resolution (21 Bits Effective) at 500 Hz AIN1 16-Bits p-p Resolution (19 Bits Effective) at 8.5 kHz 15-Bits p-p Resolution (18 Bits Effective) at 15 kHz AIN2 BUFFER On-Chip Per Channel System Calibration AIN3 24-BIT Configurable Inputs MUX - ADC AIN4 8 Single-Ended or 4 Fully Differential AIN5 Input Ranges +625 mV, +1.25 V, +2.5 V, 625 mV, 1.25 V, 2.5 V AIN6 AD7738 3-Wire Serial Interface AIN7 SCLK SPI™, QSPI™, MICROWIRE™ and DSP Compatible DOUT Schmitt Trigger on Logic Inputs CALIBRATION SERIAL AINCOM/P0 CIRCUITRY INTERFACE DIN Single-Supply Operation CS 5 V Analog Supply 3 V or 5 V Digital Supply Package: 28-Lead TSSOP RDY CLOCK CONTROL I/O PORT GENERATOR LOGIC SYNC/P1 RESET APPLICATIONS PLCs/DCS Multiplexing Applications AGND AV MCLKOUT MCLKIN DGND DV DD DD Process Control Industrial Instrumentation GENERAL DESCRIPTION
The differential reference input features “No-Reference” detect The AD7738 is a high precision, high throughput analog front capability. The ADC also supports per channel system calibra- end. True 16-bit p-p resolution is achievable with a total con- tion options. version time of 117 µs (8.5 kHz channel switching), making it The digital serial interface can be configured for 3-wire opera- ideally suitable for high resolution multiplexing applications. tion and is compatible with microcontrollers and digital signal The part can be configured via a simple digital interface, which processors. All interface inputs are Schmitt triggered. allows users to balance the noise performance against data The part is specified for operation over the extended industrial throughput up to a 15.4 kHz. temperature range of –40C to +105C. The analog front end features eight single-ended or four fully Other parts in the AD7738 family are the AD7734 and the differential input channels with unipolar or bipolar 625 mV, AD7732. 1.25 V, and 2.5 V input ranges and accepts a common-mode input voltage from 200 mV above AGND to AV The AD7734 analog front end features four single-ended input DD – 300 mV. The multiplexer output is pinned out externally, allowing the channels with unipolar or true bipolar input ranges to ± 10 V user to implement programmable gain or signal conditioning while operating from a single 5 V analog supply. The AD7734 before applying the input to the ADC. accepts an analog input overvoltage to ± 16.5 V while not degrading the performance of the adjacent channels. The AD7732 is similar to AD7734, but its analog front end features two fully differential input channels. SPI and QSPI are trademarks of Motorola, Inc. MICROWIRE is a trademark of National Semiconductor Corporation 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
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Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE PIN CONFIGURATION PIN FUNCTION DESCRIPTION PIN FUNCTION DESCRIPTION (continued) OUTPUT NOISE AND RESOLUTION SPECIFICATION CHOPPING ENABLED CHOPPING DISABLED Typical Performance Characteristics REGISTER DESCRIPTION Communications Register I/O Port Register Revision Register Test Register ADC Status Register Checksum Register ADC Zero Scale Calibration Register ADC Full-Scale Register Channel Data Registers Channel Zero-Scale Calibration Registers Channel Full-Scale Calibration Registers Channel Status Registers Channel Setup Registers Channel Conversion Time Registers Mode Register DIGITAL INTERFACE DESCRIPTION Hardware Reset Access the AD7738 Registers Single Conversion and Reading Data Dump Mode Continuous Conversion Mode Continuous Read (Continuous Conversion) Mode CIRCUIT DESCRIPTION Analog Front End Sigma-Delta ADC Chopping Multiplexer, Conversion, and Data Output Timing Frequency Response Analog Inputs Voltage Range Analog Inputs Extended Voltage Range Voltage Reference Inputs Reference Detect I/O Port CALIBRATION ADC Zero-Scale Self-Calibration Per Channel System Calibration OUTLINE DIMENSIONS