Read-Only, Pin Configured 24-Bit - ADC with Excitation Current Sources AD7783 FEATURES FUNCTIONAL BLOCK DIAGRAM Single-Channel, 24-Bit - ADC V REFIN() XTAL1 XTAL2 DD GND REFIN(+) Pin Configurable (No Programmable Registers) ISOURCE Select V DD IEXC1 IEXC2 Pin Programmable Input Ranges (2.56 V or 160 mV) 200 A 200 A IOUT1 Fixed 19.79 Hz Update Rate OSCILLATOR AND Simultaneous 50 Hz and 60 Hz Rejection PLL IOUT2 24-Bit No Missing Codes IPIN 18.5-Bit p-p Resolution (2.56 V Range) DOUT/RDY SERIAL 16.5-Bit p-p Resolution (160 mV Range) INTERFACE AIN(+) 24-BIT - AND MUX BUF PGA SCLK ADC AIN() CONTROL INTERFACE LOGIC MODE Master or Slave Mode of Operation Slave Mode CS AD7783 3-Wire Serial SPI , QSPI, MICROWIRE, and DSP-Compatible Schmitt Trigger on SCLK RANGE POWER Specified for Single 3 V and 5 V Operation BASIC CONNECTION DIAGRAM Normal: 1.3 mA 3 V Power-Down: 9 A POWER SUPPLY ON-CHIP FUNCTIONS V DD Rail-to-Rail Input Buffer and PGA AD7783 APPLICATIONS ANALOG AIN(+) CS INPUT AIN() Sensor Measurement DIGITAL DOUT/RDY INTERFACE Industrial Process Control IOUT1 CURRENT SCLK IOUT2 Temperature Measurement SOURCES XTAL1 Pressure Measurement 32.768kHz REFIN(+) REFERENCE CRYSTAL Weigh Scales XTAL2 INPUT REFIN() Portable Instrumentation GND GENERAL DESCRIPTION The device operates from a 32.768 kHz crystal with an on-chip The AD7783 is a complete analog front end for low frequency PLL generating the required internal operating frequency. The measurement applications. The 24-bit sigma-delta ADC con- output data rate from the part is fixed via the master clock at tains one fully differential input channel that can be configured 19.79 Hz and provides simultaneous 50 Hz and 60 Hz rejection with a gain of 1 or 16 allowing full-scale input signal ranges of at this update rate. At this update rate, 18-bit p-p resolution can 2.56 V or 160 mV from a +2.5 V differential reference input. be obtained. It also contains two 200 mA integrated current sources. The part operates from a single 3 V or 5 V supply. When oper- The AD7783 has an extremely simple, read-only digital inter- ating from 3 V supplies, the power dissipation for the part is face that can be operated in master mode or slave mode. 3.9 mW. The AD7783 is available in a 16-lead TSSOP. There are no on-chip registers to be programmed. The input Another part in the AD778x family is the AD7782. It is similar signal range and current source selection are configured using to the AD7783 except it has no integrated current sources and two external pins. two differential input channels. REV. C 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 registered trademarks are the property of their respective owners. Fax: Analog Devices, Inc. All rights reserved.1 AD7783SPECIFICATIONS (V = 2.7 V to 3.6 V or 4.75 V to 5.25 V, REFIN(+) = 2.5 V REFIN() = GND DD GND = 0 V XTAL1/XTAL2 = 32.768 kHz Crystal all specifications T to T , unless otherwise noted.) MIN MAX Parameter AD7783B Unit Test Conditions ADC CHANNEL SPECIFICATION Output Update Rate 19.79 Hz nom ADC CHANNEL 2 No Missing Codes 24 Bits min Resolution 16 Bits p-p 160 mV Range, RANGE = 0 18 Bits p-p 2.56 V Range, RANGE = 1 Output Noise See Table I 21 .024 REFIN FSR = Integral Nonlinearity 10 ppm of FSR max Typically 2 ppm, Gain Offset Error 3 mV typ AIN(+) = AIN() = 2.5 V Offset Error Drift versus Temperature 10 nV/ C typ Full-Scale Error 10 mV typ V = 3 V DD Gain Drift versus Temperature 0.5 ppm/ C typ Power Supply Rejection (PSR) 100 dB typ Input Range = 160 mV, V = 1/16 V IN 85 dB typ Input Range = 2.56 V, V = 1 V IN ANALOG INPUTS Differential Input Voltage Ranges 160 mV nom Range = 0 2.56 V nom Range = 1 ADC Range Matching 2 mV typ Input Voltage = 159 mV on Both Ranges Absolute AIN Voltage Limits GND + 100 mV V min V 100 mV V max DD 2 Analog Input Current DC Input Current 1nA max DC Input Current Drift 5pA/ C typ 2, 3 Normal-Mode Rejection 50 Hz 60 dB min 50 Hz 1 Hz 60 Hz 94 dB min 60 Hz 1 Hz Common-Mode Rejection Input Range = 160 mV, V = 1/16 V IN DC 105 dB min 125 dB typ, 110 dB typ when Input Range = 2.56 V 2 50 Hz 100 dB min 50 Hz 1 Hz 2 60 Hz 100 dB min 60 Hz 1 Hz REFERENCE INPUT REFIN Voltage 2.5 V nom REFIN = REFIN(+) REFIN() 2 REFIN Voltage Range 1V min V V max DD 2 Absolute REFIN Voltage Limits GND 30 mV V min V + 30 mV V max DD Average Reference Input Current 0.5 mA/V typ Average Reference Input Current Drift 0.01 nA/V/ C typ 2, 3 Normal-Mode Rejection 50 Hz 60 dB min 50 Hz 1 Hz 60 Hz 94 dB min 60 Hz 1 Hz Common-Mode Rejection Input Range = 160 mV, V = 1/16 V IN DC 100 dB typ 50 Hz 110 dB typ 50 Hz 1 Hz 60 Hz 110 dB typ 60 Hz 1 Hz EXCITATION CURRENT SOURCES (IEXC1, IEXC2) Output Current 200 mA Initial Tolerance at 25C 10 % typ Drift 200 ppm/ C typ Initial Current Matching at 25C 2.5 % max No Load Drift Matching 20 ppm/ C typ Line Regulation 2.5 mA/V max V = 5 V 5%. Typically 1.25 mA/V. DD Load Regulation 300 nA/V typ Output Compliance V 0.6 V max DD GND 30 mV V min 2 REV. C