2 LC MOS 20-Bit A/D Converter AD7703 FEATURES FUNCTIONAL BLOCK DIAGRAM Monolithic 16-Bit ADC AV DV SC1 SC2 SS SS 0.0015% Linearity Error On-Chip Self-Calibration Circuitry 7 6 4 17 Programmable Low-Pass Filter AD7703 0.1 Hz to 10 Hz Corner Frequency DV 15 DD CALIBRATION CALIBRATION 0 V to +2.5 V or 2.5 V Analog Input Range 13 CAL MICROCONTROLLER SRAM AV 4 kSPS Output Data Rate DD 14 Flexible Serial Interface Ultralow Power 20-BIT CHARGE BALANCE A/D A 9 IN 12 BP/UP CONVERTER APPLICATIONS Industrial Process Control 6-POLE GAUSSIAN ANALOG V REF 10 LOW-PASS MODULATOR 11 SLEEP Weigh Scales DIGITAL FILTER Portable Instrumentation Remote Data Acquisition AGND 8 SDATA 20 CLOCK SERIAL INTERFACE GENERATOR LOGIC 19 SCLK DGND 5 3 2 1 16 18 CLKIN CLKOUT MODE CS DRDY GENERAL DESCRIPTION PRODUCT HIGHLIGHTS The AD7703 is a 20-bit ADC that uses a S-D conversion tech- 1. The AD7703 offers 20-bit resolution coupled with outstanding nique. The analog input is continuously sampled by an analog 0.0003% accuracy. modulator whose mean output duty cycle is proportional to the 2. No missing codes ensures true, usable, 20-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 the circuitry. output data register with 16-bit binary words at word rates up to 3. The effects of temperature drift are eliminated by on-chip 4kHz. 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 accu- 4. Flexible synchronous/asynchronous interface allows the racy is ensured by self-calibration of zero and full scale, which AD7703 to interface directly to the serial ports of industry- may be initiated at any time. The self-calibration scheme can standard microcontrollers and DSP processors. also be extended to null system offset and gain errors in the input channel. 5. Low operating power consumption and an ultralow power standby mode make the AD7703 ideal for loop-powered The output data is accessed through a flexible serial port, which remote sensing applications, or battery-powered portable has an asynchronous mode compatible with UARTs and two instruments. 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.(T = 25 C AV = DV = +5 V AV = DV = 5 V V = +2.5 V f = 4.096 MHz AD7703SPECIFICATIONS A DD DD SS SS REF CLKIN 1 BP/UP = +5 V MODE = +5 V A Source Resistance = 1 k with 1 nF to AGND at A unless otherwise noted.) IN IN 2 2 2 Parameter A/S Version B Version C Version Unit Test Conditions/Comments STATIC PERFORMANCE Resolution 20 20 20 Bits Integral Nonlinearity, T to T 0.0015 0.0007 0.0003 % FSR typ MIN MAX 25C 0.003 0.0015 0.0008 % FSR max T to T 0.003 0.0015 0.0012 % FSR max MIN MAX Differential Nonlinearity, T to T 0.5 0.5 0.5 LSB typ Guaranteed No Missing Codes MIN MAX 3 Positive Full-Scale Error 4 4 4 LSB typ 16 16 16 LSB max 4 Full-Scale Drift 19/37 19 19 LSB typ 3 Unipolar Offset Error 4 4 4 LSB typ 16 16 16 LSB max 4 Unipolar Offset Drift 26 26 26 LSB typ Temp Range: 0C to +70C 67 +48/400 67 67 LSB typ Specified Temp Range 3 Bipolar Zero Error 4 4 4 LSB typ 16 16 16 LSB max 4 Bipolar Zero Drift 13 13 13 LSB typ Temp Range: 0C to +70C 34 +24/200 34 34 LSB typ Specified Temp Range 3 Bipolar Negative Full-Scale Errors 8 8 8 LSB typ 32 32 32 LSB max 4 Bipolar Negative Full-Scale Drift 10/20 10 10 LSB typ Noise (Referred to Output) 1.6 1.6 1.6 LSB rms typ DYNAMIC PERFORMANCE Sampling Frequency, f f /256 f /256 f /256 Hz S CLKIN CLKIN CLKIN Output Update Rate, f f /1024 f /1024 f /1024 Hz OUT CLKIN CLKIN CLKIN Filter Corner Frequency, f f /409,600 f /409,600 f /409,600 Hz 3 dB CLKIN CLKIN CLKIN Settling Time to 0.0007% FS 507904/f 507904/f 507904/f sec For Full-Scale Input Step CLKIN CLKIN CLKIN SYSTEM CALIBRATION Positive Full-Scale Calibration Range V + 0.1 V + 0.1 V + 0.1 V max System calibration applies to REF REF REF Positive Full-Scale Overrange V + 0.1 V + 0.1 V + 0.1 V max unipolar and bipolar ranges. REF REF REF Negative Full-Scale Overrange (V + 0.1) (V + 0.1) (V + 0.1) V max After calibration, if A > V , REF REF REF IN REF 5, 6 Maximum Offset Calibration Ranges the device will output all 1s. Unipolar Input Range (V + 0.1) (V + 0.1) (V + 0.1) V max If A < 0 (unipolar) or V REF REF REF IN REF Bipolar Input Range 0.4 V to +0.4 V 0.4 V to +0.4 V 0.4 V to +0.4 V V max (bipolar), the device will REF REF REF REF REF REF 7 Input Span 0.8 V 0.8 V 0.8 V V min output all 0s. REF REF REF 2 V + 0.2 2 V + 0.2 2 V + 0.2 V max REF REF REF ANALOG INPUT Unipolar Input Range 0 to 2.5 0 to 2.5 0 to 2.5 V Bipolar Input Range 2.5 2.5 2.5 V Input Capacitance 20 20 20 pF typ 1 Input Bias Current 111nA typ LOGIC INPUTS All Inputs Except CLKIN V , Input Low Voltage 0.8 0.8 0.8 V max INL V , Input High Voltage 2.0 2.0 2.0 V min INH CLKIN V , Input Low Voltage 0.8 0.8 0.8 V max INL V , Input High Voltage 3.5 3.5 3.5 V min INH I , Input Current 10 10 10 A max IN LOGIC OUTPUTS V , Output Low Voltage 0.4 0.4 0.4 V max I = 1.6 mA OL SINK V , Output High Voltage DV 1DV 1DV 1V min I = 100 A OH DD DD DD SOURCE Floating State Leakage Current 10 10 10 A max Floating State Output Capacitance999pF typ POWER REQUIREMENTS Power Supply Voltages Analog Positive Supply (AV ) 4.5/5.5 4.5/5.5 4.5/5.5 V min/V max For Specified Performance DD Digital Positive Supply (DV ) 4.5/AV 4.5/AV 4.5/AV V min/V max DD DD DD DD Analog Negative Supply (AV ) 4.5/5.5 4.5/5.5 4.5/5.5 V min/V max SS Digital Negative Supply (DV ) 4.5/5.5 4.5/5.5 4.5/5.5 V min/V max SS Calibration Memory Retention Power Supply Voltage 2.0 2.0 2.0 V min 2 REV. 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