Datasheet AD7701 (Analog Devices)

LC2MOS 16-Bit A/D Converter AD7701 FEATURES FUNCTIONAL BLOCK DIAGRAM Monolithic 16-Bit ADC 0.0015% Linearity Error AVDD DVDD AVSS DVSS SC1 SC2 On-Chip Self-Calibration Circuitry 14 15 7 6 4 17 Programmable Low-Pass Filter AD7701 0.1 Hz to 10 Hz Corner Frequency 0 V to +2.5 V or 2.5 V Analog Input Range CALIBRATION CALIBRATION 13 CAL SRAM MICROCONTROLLER 4 kSPS Output Data Rate Flexible Serial Interface Ultralow Power 16-BIT A/D CONVERTER AIN 9 12 BP/UP APPLICATIONS 6-POLE GAUSSIAN ANALOG Industrial Process Control LOW-PASS MODULATOR V 10 DIGITAL FILTER REF Weigh Scales 11 SLEEP Portable Instrumentation Remote Data Acquisition AGND 8 20 CLOCK SERIAL INTERFACE SDATA GENERATOR LOGIC 19 SCLK DGND 5 3 2 1 16 18 CLKIN CLKOUT MODE CS DRDY GENERAL DESCRIPTION PRODUCT HIGHLIGHTS
The AD7701 is a 16-bit ADC that uses a sigma-delta conversion 1. The AD7701 offers 16-bit resolution coupled with outstand- technique. The analog input is continuously sampled by an analog ing 0.0015% accuracy. modulator whose mean output duty cycle is proportional to the 2. No missing codes ensures true, usable, 16-bit dynamic range, input signal. The modulator output is processed by an on-chip removing the need for programmable gain and level-setting digital filter with a six-pole Gaussian response, which updates circuitry. the output data register with 16-bit binary words at word rates up 3. The effects of temperature drift are eliminated by on-chip to 4 kHz. The sampling rate, filter corner frequency, and output self-calibration, which removes zero and gain error. External word rate are set by a master clock input that may be supplied circuits can also be included in the calibration loop to remove externally, or by a crystal controlled on-chip clock oscillator. system offsets and gain errors. The inherent linearity of the ADC is excellent and endpoint 4. A flexible synchronous/asynchronous interface allows the accuracy is ensured by self-calibration of zero and full scale, AD7701 to interface directly to UARTs or to the serial ports which may be initiated at any time. The self-calibration scheme of industry-standard microcontrollers. can also be extended to null system offset and gain errors in the 5. Low operating power consumption and an ultralow power input channel. standby mode make the AD7701 ideal for loop-powered remote sensing applications, or battery-powered portable The output data is accessed through a flexible serial port, which instruments. has an asynchronous mode compatible with UARTs and two synchronous modes suitable for interfacing to shift registers or the serial ports of industry-standard microcontrollers. CMOS construction ensures low power dissipation, and a power- down mode reduces the idle power consumption to only 10 µW. REV. E 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. No license is granted by implication or otherwise
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Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE PIN CONFIGURATIONS PIN FUNCTION DESCRIPTIONS TIMING CHARACTERISTICS DEFINITION OF TERMS Linearity Error Differential Linearity Error Positive Full-Scale Error Unipolar Offset Error Bipolar Zero Error Bipolar Negative Full-Scale Error Positive Full-Scale Overrange Negative Full-Scale Overrange Offset Calibration Range Full-Scale Calibration Range Input Span GENERAL DESCRIPTION THEORY OF OPERATION DIGITAL FILTERING FILTER CHARACTERISTICS USING THE AD7701 SYSTEM DESIGN CONSIDERATIONS CLOCKING ANALOG INPUT RANGES INPUT SIGNAL CONDITIONING Source Resistance Antialias Considerations VOLTAGE REFERENCE CONNECTIONS GROUNDING AND SUPPLY DECOUPLING ACCURACY AND AUTOCALIBRATION CALIBRATION RANGE POWER-UP AND CALIBRATION POWER SUPPLY SEQUENCING GROUNDING SINGLE-SUPPLY OPERATION SLEEP MODE DIGITAL INTERFACE Synchronous Self-Clocking Mode (SSC) Synchronous External Clock Mode (SEC) Asynchronous Communications (AC) Mode DIGITAL NOISE AND OUTPUT LOADING OUTLINE DIMENSIONS Revision History