8-Channel, High Throughput, a 24-Bit - ADC AD7738 FUNCTIONAL BLOCK DIAGRAM FEATURES High Resolution ADC MUXOUT ADCIN REFIN REFIN+ 24 Bits No Missing Codes 0.0015% Nonlinearity REFERENCE DETECT Optimized for Fast Channel Switching AIN0 18-Bits p-p Resolution (21 Bits Effective) at 500 Hz AIN1 16-Bits p-p Resolution (19 Bits Effective) at 8.5 kHz AIN2 BUFFER 15-Bits p-p Resolution (18 Bits Effective) at 15 kHz AIN3 On-Chip Per Channel System Calibration 24-BIT MUX - ADC Configurable Inputs AIN4 8 Single-Ended or 4 Fully Differential AIN5 Input Ranges AIN6 +625 mV, +1.25 V, +2.5 V, 625 mV, 1.25 V, 2.5 V AD7738 3-Wire Serial Interface AIN7 SCLK SPI, QSPI, MICROWIRE and DSP Compatible DOUT CALIBRATION SERIAL Schmitt Trigger on Logic Inputs AINCOM/P0 CIRCUITRY INTERFACE DIN Single-Supply Operation CS 5 V Analog Supply 3 V or 5 V Digital Supply RDY Package: 28-Lead TSSOP CLOCK CONTROL I/O PORT GENERATOR LOGIC SYNC/P1 RESET APPLICATIONS PLCs/DCS AGND AV MCLKOUT MCLKIN DGND DV Multiplexing Applications 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 s (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 40 C to +105 C. 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 The AD7734 analog front end features four single-ended input input voltage from 200 mV above AGND to AV 300 mV. DD channels with unipolar or true bipolar input ranges to 10 V The multiplexer output is pinned out externally, allowing the while operating from a single 5 V analog supply. The AD7734 user to implement programmable gain or signal conditioning accepts an analog input overvoltage to 16.5 V while not before applying the input to the ADC. 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. use, nor for any infringements of patents or other rights of third parties that Tel: 781/329-4700 www.analog.com may result from its use. No license is granted by implication or otherwise Fax: 781/326-8703 Analog Devices, Inc., 2002 under any patent or patent rights of Analog Devices.AD7738SPECIFICATIONS (40 C to +105 C, AV = 5 V 5%, DV = 2.7 V to 3.6 V or 5 V 5%, DD DD REFIN(+) = 2.5 V, REFIN() = 0 V, AINCOM = 2.5 V, MUXOUT(+) = ADCIN(+), MUXOUT() = ADCIN(), Internal Buffer ON, AIN Range = 1.25 V, f = 6.144 MHz unless otherwise noted.) MCLK Parameter Min Typ Max Unit Test Conditions/Comment ADC PERFORMANCE CHOPPING ENABLED Conversion Time Rate 372 12190 Hz Configure via Conversion Time Register 1 No Missing Codes 24 Bits FW 6 (Conversion Time 165 s) See Typical Performance Characteristics Output Noise See Table I Resolution See Tables II and III Integral Nonlinearity (INL) 0.0015 % of FSR AIN Range = 2.5 V 0.0015 % of FSR AIN Range = 1.25 V 2 Offset Error (Unipolar, Bipolar) 10 V Before Calibration 1 Offset Drift vs. Temperature 280 nV/C 2 Gain Error 0.2 % Before Calibration 1 Gain Drift vs. Temperature 2.5 ppm of FS/ C 2 Positive Full-Scale Error 0.2 % of FSR Before Calibration 1 Positive Full-Scale Drift vs. Temperature 2.5 ppm of FS/ C 3 3 Bipolar Negative Full-Scale Error 0.0030 % of FSR After Calibration Common-Mode Rejection 80 100 dB At DC, AIN = 1 V Power Supply Rejection 70 80 dB At DC, AIN = 1 V ADC PERFORMANCE CHOPPING DISABLED Conversion Time Rate 737 15437 Hz Configure via Conversion Time Register 1 No Missing Codes 24 Bits FW 8 (Conversion Time 117 s) See Typical Perfomance Charateristics Output Noise See Table IV Resolution See Tables V and VI Integral Nonlinearity (INL) 0.0015 % of FSR 4 Offset Error (Unipolar, Bipolar) 1mV Before Calibration Offset Drift vs. Temperature 1.5 V/ C 2 Gain Error 0.2 % Before Calibration Gain Drift vs. Temperature 2.5 ppm of FS/ C 2 Positive Full-Scale Error 0.2 % of FSR Before Calibration Positive Full-Scale Drift vs. Temperature 2.5 ppm of FS/ C 3 3 Bipolar Negative Full-Scale Error 0.0030 % of FSR After Calibration Common-Mode Rejection 75 dB At DC, AIN = 1 V Power Supply Rejection 65 dB At DC, AIN = 1 V ANALOG INPUTS 1, 5 Analog Input Voltage Ranges 2.5 V Range 2.9 2.5 +2.9 V +2.5 V Range 0 0 to 2.5 2.9 V 1.25 V Range 1.45 1.25 +1.45 V +1.25 V Range 0 0 to 1.25 1.45 V 0.625 V Range 725 625 +725 mV +0.625 V Range 0 0 to 625 725 mV 1 AIN, AINCOM Common-Mode Voltage 0.2 AV 0.3 V DD 6 AIN, AINCOM Input Current 200 nA Only One Channel, Chop Disabled 1 AIN to MUXOUT On Resistance 200 REFERENCE INPUT 1, 7 REFIN(+) to REFIN() Voltage 2.475 2.5 2.525 V NOREF Trigger Voltage 0.5 V NOREF Bit in Channel Status Register REFIN(+), REFIN() 1 Common-Mode Voltage 0AV V DD 8 Reference Input Current 400 A 1, 9 SYSTEM CALIBRATION Full Scale Calibration Limit +1.05 FS V Zero Scale Calibration Limit 1.05 FS V Input Span 0.8 FS 2.1 FS V 2 REV. 0