2 LC MOS 16-Bit A/D Converter AD7701 FEATURES FUNCTIONAL BLOCK DIAGRAM Monolithic 16-Bit ADC AV DV AV DV SC1 SC2 DD DD SS SS 0.0015% Linearity Error 14 15 7 64 17 On-Chip Self-Calibration Circuitry Programmable Low-Pass Filter AD7701 0.1 Hz to 10 Hz Corner Frequency CALIBRATION CALIBRATION 0 V to +2.5 V or 2.5 V Analog Input Range 13 CAL SRAM MICROCONTROLLER 4 kSPS Output Data Rate Flexible Serial Interface Ultralow Power 16-BIT A/D CONVERTER A IN 9 12 BP/UP 6-POLE GAUSSIAN APPLICATIONS ANALOG LOW-PASS Industrial Process Control MODULATOR V DIGITAL FILTER 10 REF 11 SLEEP Weigh Scales Portable Instrumentation Remote Data Acquisition AGND 8 20 SDATA CLOCK SERIAL INTERFACE 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. 4. A flexible synchronous/asynchronous interface allows the The inherent linearity of the ADC is excellent and endpoint AD7701 to interface directly to UARTs or to the serial ports accuracy is ensured by self-calibration of zero and full scale, of industry-standard microcontrollers. which may be initiated at any time. The self-calibration scheme 5. Low operating power consumption and an ultralow power can also be extended to null system offset and gain errors in the standby mode make the AD7701 ideal for loop-powered input channel. 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 W. 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. may result from its use. No license is granted by implication or otherwise Tel: 781/329-4700 www.analog.com under any patent or patent rights of Analog Devices. Trademarks and Fax: 781/326-8703 2003 Analog Devices, Inc. All rights reserved. registered trademarks are the property of their respective companies.AD7701SPECIFICATIONS (T = 25 C AV = DV = +5 V AV = DV = 5 V V = +2.5 V f = 4.096 MHz A DD DD SS SS REF CLKIN 1 Bipolar Mode: MODE = +5 V A Source Resistance = 1k with 1 nF to AGND at A unless otherwise noted.) IN IN 2 2 Parameter A, S Version B, T Version Unit Test Conditions/Comments STATIC PERFORMANCE Resolution 16 16 Bits Integral Nonlinearity T to T 0.0007 % FSR typ MIN MAX 0.003 0.0015 % FSR max Differential Nonlinearity T to T 0.125 0.125 LSB typ Guaranteed No Missing Codes MIN MAX 0.5 0.5 LSB max 3 Positive Full-Scale Error 0.13 0.13 LSB typ 0.5 0.5 LSB max 4 Full-Scale Drift 1.2 (2.3 S Version) 1.2 (2.3 T Version) LSB typ 3 Unipolar Offset Error 0.25 0.25 LSB typ 1 1 LSB max 4 Unipolar Offset Drift 1.6 (+3/25 S Version) 1.6 (+3/25 T Version) LSB typ 3 Bipolar Zero Error 0.25 0.25 LSB typ 1 1 LSB max 4 Bipolar Zero Drift 0.8 (+1.5/12.5 S Version) 0.8 (+1.5/12.5 T Version) LSB typ 3 Bipolar Negative Full-Scale Error 0.5 0.5 LSB typ 2 2 LSB max 4 Bipolar Negative Full-Scale Drift 0.6 (1.2 S Version) 0.6 (1.2 T Version) LSB typ Noise (Referred to Output) 0.1 0.1 LSB rms typ DYNAMIC PERFORMANCE Sampling Frequency, f f /256 f /256 Hz S CLKIN CLKIN Output Update Rate, f f /1024 f /1024 Hz OUT CLKIN CLKIN Filter Corner Frequency, f f /409,600 f /409,600 Hz 3 dB CLKIN CLKIN Settling Time to 0.0007% FS 507904/f 507904/f sec For Full-Scale Input Step CLKIN CLKIN SYSTEM CALIBRATION Applies to unipolar and Positive Full-Scale Overrange V + 0.1 V + 0.1 V max bipolar ranges. After cali- REF REF Positive Full-Scale Overrange V + 0.1 V + 0.1 V max bration, if A > V , the REF REF IN REF Negative Full-Scale Overrange (V + 0.1) (V + 0.1) V max device will output all 1s. REF REF 5, 6 Maximum Offset Calibration Range If A < 0 (unipolar) or IN Unipolar Input Range (V + 0.1) (V + 0.1) V max V (bipolar), the device REF REF REF Bipolar Input Range 0.4 V to +0.4 V 0.4 V to +0.4 V V max will output all 0s. REF REF REF REF 7 Input Span 0.8 V 0.8 V V min REF REF 2 V + 0.2 2 V + 0.2 V max REF REF ANALOG INPUT Unipolar Input Range 0 to 2.5 0 to 2.5 V Bipolar Input Range 2.5 2.5 V Input Capacitance 10 10 pF typ 1 Input Bias Current 11 nA typ LOGIC INPUTS All Inputs Except CLKIN V , Input Low Voltage 0.8 0.8 V max INL V , Input High Voltage 2.0 2.0 V min INH CLKIN V , Input Low Voltage 0.8 0.8 V max INL V , Input High Voltage 3.5 3.5 V min INH I , Input Current 10 10 A max IN LOGIC OUTPUTS V , Output Low Voltage 0.4 0.4 V max I = 1.6 mA OL SINK V , Output High Voltage DV 1 DV 1 V min I = 100 A OH DD DD SOURCE Floating State Leakage Current 10 10 A max Floating State Output Capacitance 9 9 pF typ 2 REV. E