Read Only, Pin Configured a 24-Bit - ADC AD7782 FEATURES FUNCTIONAL BLOCK DIAGRAM 2-Channel, 24-Bit - ADC V GND REFIN(+) REFIN() XTAL1 XTAL2 DD Pin Configurable (No Programmable Registers) Pin Selectable Input Channels Pin Programmable Input Ranges ( 2.56 V or 160 mV) OSCILLATOR Fixed 19.79 Hz Update Rate AD7782 AND PLL Simultaneous 50 Hz and 60 Hz Rejection 24-Bit No Missing Codes 18.5-Bit p-p Resolution ( 2.56 V Range) AIN1(+) SERIAL DOUT/RDY INTERFACE 24-BIT - AIN1() 16.5-Bit p-p Resolution ( 160 mV Range) MUX BUF PGA AND SCLK ADC CONTROL AIN2(+) LOGIC MODE INTERFACE AIN2() Master or Slave Mode of Operation Slave Mode CS 3-Wire Serial SPI, QSPI, MICROWIRE, and DSP-Compatible CH1/CH2 RANGE Schmitt Trigger on SCLK POWER Specified for Single 3 V and 5 V Operation BASIC CONNECTION DIAGRAM Normal: 1.3 mA 3 V POWER SUPPLY Power-Down: 9 A ON-CHIP FUNCTIONS V DD Rail-Rail Input Buffer and PGA AD7782 AIN1(+) ANALOG CS APPLICATIONS INPUT AIN1() DIGITAL DOUT/RDY Sensor Measurement INTERFACE ANALOG AIN2(+) SCLK Industrial Process Control INPUT AIN2() XTAL1 Temperature Measurement 32.768kHz REFIN(+) REFERENCE Pressure Measurements CRYSTAL XTAL2 INPUT REFIN() Weigh Scales GND Portable Instrumentation GENERAL DESCRIPTION The device operates from a 32.768 kHz crystal with an on-chip PLL The AD7782 is a complete analog front end for low-frequency generating the required internal operating frequency. The output measurement applications. The 24-bit sigma-delta ADC contains data rate from the part is fixed via the master clock at 19.79 Hz and two fully differential analog input channels that can be config- provides simultaneous 50 Hz and 60 Hz rejection at this update ured with a gain of 1 or 16 allowing full-scale input signal ranges rate. Eighteen-bit p-p resolution can be obtained at this update rate. of 2.56 V or 160 mV from a +2.5 V differential reference The part operates from a single 3 V or 5 V supply. When operating input. from 3 V supplies, the power dissipation for the part is 3.9 mW. The AD7782 has an extremely simple, read-only digital interface The AD7782 is available in a 16-lead TSSOP package. which can be operated in master mode or slave mode. There are Another part in the AD778x family is the AD7783. It is similar no on-chip registers to be programmed. The input signal range to the AD7782 except it has two integrated current sources and and input channel selection are configured using two external pins. only one differential input channel. SPI and QSPI are trademarks of Motorola Inc. MICROWIRE is a trademark of National Semiconductor Corporation. REV. A 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 under any patent or patent rights of Analog Devices. Fax: 781/326-8703 Analog Devices, Inc., 2012(V = 2.7 V to 3.6 V or 4.75 V to 5.25 V, REFIN(+) = 2.5 V REFIN() = GND GND = 0 V DD AD7782SPECIFICATIONS XTAL1/XTAL2 = 32.768 kHz Crystal all specifications T to T unless otherwise noted.) MIN MAX Parameter AD7782B 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 2 1.024 REFIN Integral Nonlinearity 10 ppm of FSR max Typically 2 ppm FSR = Gain Offset Error 3 V typ AIN(+) = AIN() = 2.5 V Offset Error Drift vs. Temperature 10 nV/C typ Full-Scale Error 10 V typ V = 3 V DD Gain Drift vs. 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 V 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 1 nA max DC Input Current Drift 5 pA /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 1V min REFIN Voltage Range V V max DD 2 Absolute REFIN Voltage Limits GND 30 mV V min + 30 mV V max V DD Average Reference Input Current 0.5 A/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 = 1/16 V Common-Mode Rejection Input Range = 160 mV, V IN DC 100 dB typ 50 Hz 110 dB typ 50 Hz 1 Hz 60 Hz 110 dB typ 60 Hz 1 Hz LOGIC INPUTS 2 All Inputs Except SCLK and XTAL1 V , Input Low Voltage 0.8 V max V = 5 V INL DD 0.4 V max V = 3 V DD V , Input High Voltage 2.0 V min V = 3 V or 5 V INH DD 2 SCLK Only (Schmitt-Triggered Input) V 1.4/2 V min/V max V = 5 V T(+) DD V 0.8/1.4 V min/V max V = 5 V T() DD V V 0.3/0.85 V min/V max V = 5 V T(+) T() DD V 0.95/2 V min/V max V = 3 V T(+) DD V 0.4/1.1 V min/V max V = 3 V T() DD V V 0.3/0.85 V min/V max V = 3 V T(+) T() DD REV. A 2