Datasheet AD7908, AD7918, AD7928 (Analog Devices)

8-Channel, 1 MSPS, 8-/10-/12-Bit ADCs with Sequencer in 20-Lead TSSOP Data Sheet AD7908/ AD7918/ AD7928 FEATURES FUNCTIONAL BLOCK DIAGRAM Fast throughput rate: 1 MSPS AVDD Specified for AVDD of 2.7 V to 5.25 V Low power REFIN 6.0 mW max at 1 MSPS with 3 V supply VIN0 T/H 13.5 mW max at 1 MSPS with 5 V supply • • 8-/10-/12-BIT SUCCESSIVE Eight (single-ended) inputs with sequencer • • APPROXIMATION ADC Wide input bandwidth • • I/P AD7928, 70 d B min SINAD at 50 kHz input frequency • MUX • Flexible power/serial clock speed management • • No pipeline delays • • High speed serial interface SPI®/QSPI™/ • VIN7 MICROWIRE™/DSP compatible SCLK Shutdown mode: 0.5 μA max DOUT 20-lead TSSOP package SEQUENCER CONTROL LOGIC DIN Qualified for automotive applications CS AD7908/AD7918/AD7928 GENERAL DESCRIPTION VDRIVE
001
GND
03089- The AD7908/AD7918/AD7928 are, respectively, 8-bit, 10-bit, and Figure 1. 12-bit, high speed, low power, 8-channel, successive approximation ADCs. The parts operate from a single 2.7 V to 5.25 V power
PRODUCT HIGHLIGHTS
supply and feature throughput rates up to 1 MSPS. The parts 1. High Throughput with Low Power Consumption. The AD7908/ contain a low noise, wide bandwidth track-and-hold amplifier that AD7918/AD7928 offer up to 1 MSPS throughput rates. At the can handle input frequencies in excess of 8 MHz. maximum throughput rate with 3 V supplies, the AD7908/ The conversion process and data acquisition are controlled using AD7918/AD7928 dissipate just 6 mW of power maximum. CS and the serial clock signal, allowing the device to easily interface 2. Eight Single-Ended Inputs with a Channel Sequencer. with microprocessors or DSPs. The input signal is sampled on the A sequence of channels can be selected, through which fal ing edge of CS and conversion is also initiated at this point. the ADC cycles and converts on. There are no pipeline delays associated with the part. 3. Single-Supply Operation with VDRIVE Function. The AD7908/ The AD7908/AD7918/AD7928 use advanced design techniques to AD7918/AD7928 operate from a single 2.7 V to 5.25 V supply. achieve very low power dissipation at maximum throughput rates. The VDRIVE function al ows the serial interface to connect directly At maximum throughput rates, the AD7908/AD7918/AD7928 to either 3 V or 5 V processor systems independent of AVDD. consume 2 mA maximum with 3 V supplies; with 5 V supplies, the current consumption is 2.7 mA maximum. 4. Flexible Power/Serial Clock Speed Management. The conversion rate is determined by the serial clock, al owing the conversion Through the configuration of the control register, the analog input time to be reduced through the serial clock speed increase. The range for the part can be selected as 0 V to REFIN or 0 V to 2 × parts also feature various shutdown modes to maximize power REFIN, with either straight binary or twos complement output efficiency at lower throughput rates. Current consumption is coding. The AD7908/AD7918/AD7928 each feature eight single- 0.5 μA max when in ful shutdown. ended analog inputs with a channel sequencer to allow a preprogrammed selection of channels to be converted sequential y. 5. No Pipeline Delay. The parts feature a standard successive approximation ADC with accurate control of the sampling The conversion time for the AD7908/AD7918/AD7928 is instant via a CS input and once off conversion control. determined by the SCLK frequency, which is also used as the master clock to control the conversion.
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Document Outline Features General Description Functional Block Diagram Product Highlights Revision History Specifications AD7908 Specifications AD7918 Specifications AD7928 Specifications Timing Specifications Absolute Maximum Ratings ESD Caution Pin Configuration and Function Descriptions Terminology Typical Performance Characteristics Performance Curves Control Register Sequencer Operation SHADOW Register Circuit Information Converter Operation Analog Input ADC Transfer Function Handling Bipolar Input Signals Typical Connection Diagram Analog Input Selection Digital Inputs VDRIVE Reference Modes of Operation Normal Mode (PM1 = PM0 = 1) Full Shutdown Mode (PM1 = 1, PM0 = 0) Auto Shutdown Mode (PM1 = 0, PM0 = 1) Powering Up the AD7908/AD7918/AD7928 Power vs. Throughput Rate Serial Interface Microprocessor Interfacing AD7908/AD7918/AD7928 to TMS320C541 AD7908/AD7918/AD7928 to ADSP-21xx AD7908/AD7918/AD7928 to DSP563xx Application Hints Grounding and Layout Evaluating the AD7908/AD7918/AD7928 Performance Outline Dimensions Ordering Guide Automotive Products