AD7785BRUZ Analog Devices Inc, AD7785BRUZ Datasheet
AD7785BRUZ
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AD7785BRUZ Summary of contents
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FEATURES bits effective resolution RMS noise 4. 16.7 Hz Current: 400 μA typical Power-down: 1 μA maximum Low noise programmable gain instrumentation amp Band gap reference with 4 ppm/°C drift ...
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AD7785 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Characteristics..................................................................... 6 Timing Diagrams.......................................................................... 7 Absolute Maximum Ratings............................................................ 8 ESD Caution.................................................................................. 8 Pin Configuration and ...
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SPECIFICATIONS 5.25 V; GND = 0 V; all specifications Table 1. Parameter ADC CHANNEL Output Update Rate 2 No Missing Codes Resolution Output Noise and ...
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AD7785 Parameter REFERENCE Internal Reference Internal Reference Initial Accuracy 2 Internal Reference Drift Power Supply Rejection External Reference External REFIN Voltage 2 Reference Voltage Range 2 Absolute REFIN Voltage Limits Average Reference Input Current Average Reference Input Current Drift Normal ...
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Parameter SCLK, CLK, and DIN (Schmitt- Triggered Input (+) T V (– (+) − V (− (+) T V (– (+) − V (− Input Currents Input Capacitance LOGIC ...
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AD7785 TIMING CHARACTERISTICS 5.25 V, GND = 0 V, Input Logic Input Logic Table Parameter Limit ...
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TIMING DIAGRAMS DOUT/RDY ( MSB SCLK ( NOTES INPUT OUTPUT Figure 3. Read Cycle Timing Diagram CS ( SCLK ( ...
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AD7785 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 3. Parameter AV to GND GND DD Analog Input Voltage to GND Reference Input Voltage to GND Digital Input Voltage to GND Digital Output Voltage ...
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PIN CONFIGURATION AND FUNCTION DESCRIPTIONS Table 4. Pin Function Descriptions Pin No. Mnemonic Description 1 SCLK Serial Clock Input. This serial clock input is for data transfers to and from the ADC. The SCLK has a Schmitt- triggered input, making ...
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AD7785 Pin No. Mnemonic Description 15 DOUT/RDY Serial Data Output/Data Ready Output. DOUT/RDY serves a dual purpose. It functions as a serial data output pin to access the output shift register of the ADC. The output shift register can contain ...
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OUTPUT NOISE AND RESOLUTION SPECIFICATIONS EXTERNAL REFERENCE Table 5 shows the output rms noise of the AD7785 for some of the update rates and gain settings. The numbers given are for the bipolar input range with an external 2.5 V ...
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AD7785 INTERNAL REFERENCE Table 7 shows the output rms noise of the AD7785 for some of the update rates and gain settings. The numbers given are for the bipolar input range with the internal 1.17 V reference. These numbers are ...
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TYPICAL PERFORMANCE CHARACTERISTICS 8388800 8388750 8388700 8388650 8388600 8388550 8388500 8388450 0 200 400 READING NUMBER Figure 6. Typical Noise Plot (Internal Reference, Gain = 64, Update Rate = 16.7 Hz ...
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AD7785 ON-CHIP REGISTERS The ADC is controlled and configured via a number of on-chip registers, which are described on the following pages. In the following descriptions, set implies a Logic 1 state and cleared implies a Logic 0 state, unless ...
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STATUS REGISTER RS2, RS1, RS0 = Power-On/Reset = 0x88 The status register is an 8-bit read-only register. To access the ADC status register, the user must write to the communications register, select the next operation to be ...
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AD7785 Table 13. Operating Modes MD2 MD1 MD0 Mode Continuous Conversion Mode (Default). In continuous conversion mode, the ADC continuously performs conversions and places the result in the data register. RDY goes low when a conversion is ...
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FS3 FS2 FS1 FS0 CONFIGURATION REGISTER RS2, RS1, RS0 = 0, 1, ...
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AD7785 Bit Location Bit Name Description CON7 REFSEL Reference Select Bit. The reference source for the ADC is selected using this bit. REFSEL 0 1 CON6 to 0 These bits must be programmed with a Logic 0 for correct operation. ...
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Table 16. IO Register Bit Designations Bit Location Bit Name Description IO7 to IO4 0 These bits must be programmed with a Logic 0 for correct operation. IO3 to IO2 IEXCDIR1 to Direction of current sources select bits. IEXCDIR0 IEXCDIR1 ...
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AD7785 ADC CIRCUIT INFORMATION OVERVIEW The AD7785 is a low power ADC that incorporates a ∑-Δ modulator, a buffer, reference, in-amp, and an on-chip digital filter intended for the measurement of wide dynamic range, low frequency signals such as those ...
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FREQUENCY (Hz) Figure 14. Filter Profile with Update Rate = 16 –20 –40 –60 –80 –100 0 500 1000 1500 2000 FREQUENCY (Hz) Figure ...
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AD7785 Figure 3 and Figure 4 show timing diagrams for interfacing to the AD7785 with CS being used to decode the part. Figure 3 shows the timing for a read operation from the AD7785 output shift register, and Figure 4 ...
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CS 0x08 DIN DOUT/RDY SCLK CS DIN DOUT/RDY SCLK 0x200A Figure 17. Single Conversion 0x58 DATA Figure 18. Continuous Conversion Rev Page 0x58 DATA 0x58 AD7785 DATA ...
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AD7785 Continuous Read Rather than write to the communications register to access the data each time a conversion is complete, the AD7785 can be configured so that the conversions are placed on the DOUT/ RDY line automatically. By writing 01011100 ...
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CIRCUIT DESCRIPTION ANALOG INPUT CHANNEL The AD7785 has three differential analog input channels. These are connected to the on-chip buffer amplifier when the device is operated in buffered mode and directly to the modulator when the device is operated in ...
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AD7785 BURNOUT CURRENTS Burnout currents are available on Channels AIN1 and AIN2. The burnout currents are 100 nA constant current generators, one sourcing current from AV to AIN(+) and one sinking DD current from AIN(–) to GND. The currents are ...
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AV MONITOR DD Along with converting external voltages, the ADC can be used to monitor the voltage on the AV DD Bit CH0 equal 1, the voltage on the AV DD attenuated by 6, and the resultant voltage is applied ...
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AD7785 The ground planes of the AD7785 should be allowed to run under the device to prevent noise coupling. The power supply lines to the AD7785 should use as wide a trace as possible to provide low impedance paths and ...
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APPLICATIONS INFORMATION The AD7785 provides a low cost, high resolution analog-to- digital function. Because the analog-to-digital function is provided by a ∑-Δ architecture, the part is more immune to noisy environments, making it ideal for use in sensor measurement and ...
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AD7785 TEMPERATURE MEASUREMENT USING AN RTD To optimize a 3-wire RTD configuration, two identically matched current sources are required. The AD7785, which contains two well-matched current sources, is ideally suited to these applications. One possible 3-wire configuration is shown in ...
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... OUTLINE DIMENSIONS 0.15 0.05 ORDERING GUIDE Model Temperature Range 1 AD7785BRUZ –40°C to +105°C 1 AD7785BRUZ-REEL –40°C to +105°C 1 EVAL-AD7785EBZ RoHS Compliant Part. 5.10 5.00 4. 4.50 6.40 4.40 BSC 4. PIN 1 1.20 MAX 0.20 0.09 8° 0.30 0.65 0° 0.19 SEATING BSC ...
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AD7785 NOTES ©2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06721-0-4/07(0) Rev Page ...