AD7796 Analog Devices, AD7796 Datasheet
AD7796
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AD7796 Summary of contents
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... The devices can be operated with the internal clock or an external clock. The output data rate from the parts is software- programmable and can be varied from 4. 123 Hz. The AD7796/AD7797 operate with a power supply from 2 5.25 V. Each part consumes a current of 250 μA typical and is housed in a 16-lead TSSOP. ...
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... AD7796/AD7797 TABLE OF CONTENTS Features .............................................................................................. 1 Interface ............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Functional Block Diagram .............................................................. 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Characteristics..................................................................... 5 Timing Diagrams.......................................................................... 6 Absolute Maximum Ratings............................................................ 7 Thermal Resistance ...................................................................... 7 ESD Caution.................................................................................. 7 Pin Configuration and Function Descriptions............................. 8 RMS Noise and Resolution Specifications .................................... 9 Typical Performance Characteristics ........................................... 10 On-Chip Registers .......................................................................... 11 Communication Register .......................................................... 11 Status Register ...
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... Rev Page AD7796/AD7797 , unless otherwise noted. MAX Test Conditions/Comments AD7797 only AD7796 only AIN = 1 V/128 V = REFIN(+) – REFIN(–) REF V = (AIN(+) + AIN(–))/2 CM Update rate < 100 typ, 50 ± 1 Hz, 60 ± 1 Hz, FS[3:0] = 1010 90 dB typ, 50 ± 1 Hz, FS[3:0] = 1001 ...
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... Full-scale error applies to both positive and negative full-scale and applies at the factory calibration conditions (AV 6 FS[3:0] are the four bits used in the mode register to select the output word rate. 7 Digital inputs equal GND AD7796B/AD7797B Unit 64 ± 3% kHz min/max 50:50 % typ 64 kHz nom ...
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... OUTPUT 1.6V PIN 50pF I (200µA WITH DV SOURCE 100µA WITH DV = 3V) DD Figure 2. Load Circuit for Timing Characterization Rev Page AD7796/AD7797 , unless otherwise noted (10 and timed from a voltage level of 1 limits ...
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... AD7796/AD7797 TIMING DIAGRAMS DOUT/RDY (O) SCLK ( MSB SCLK ( INPUT OUTPUT Figure 3. Read Cycle Timing Diagram CS ( DIN (I) MSB I = INPUT Figure 4. Write Cycle Timing Diagram Rev Page LSB LSB ...
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... Package Type −0 0 TSSOP −0 0 −0 0 −0 0.3 V ESD CAUTION −40°C to +85°C −65°C to +150°C 150°C 215°C 220°C Rev Page AD7796/AD7797 θ θ Unit JA JC 128 14 °C/W ...
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... Serial Data Input. This serial data input accesses the input shift register on the ADC. Data in this shift register is transferred to the control registers within the ADC; the register selection bits of the communication register identify the appropriate register. SCLK 16 DIN 1 CLK 2 DOUT/RDY 15 AD7796 AD7797 TOP VIEW ...
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... RMS NOISE AND RESOLUTION SPECIFICATIONS Table 6 shows the rms noise of the AD7796/AD7797 for some of the update rates. The numbers given are for the bipolar input range with an external 2.5 V reference. These numbers are typical and are generated with a differential input voltage ...
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... AD7796/AD7797 TYPICAL PERFORMANCE CHARACTERISTICS –20 –40 0 100 200 300 400 500 600 SAMPLES Figure 6. AD7797 Noise ( Update Rate = 16.7 Hz) REF DD 17.5 15.0 12.5 10.0 7.5 5.0 2.5 0 8388485 8388550 8388600 8388650 CODE Figure 7. AD7797 Noise Distribution Histogram ( Update Rate = 16.7 Hz) REF DD 2.0 1.5 1.0 0.5 –0.5 –1.0 –1.5 –2.0 ...
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... CR4 CR3 CR2 RS1(0) RS0(0) CREAD(0) Rev Page AD7796/AD7797 LSB CR1 CR0 0(0) 0(0) Register Size 8 bits 8 bits 16 bits 16 bits 16 bits (AD7796), 24 bits (AD7797) 8 bits 8 bits 16 bits (AD7796), 24 bits (AD7797) 16 bits (AD7796), 24 bits (AD7797) ...
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... CLK1 to CLK0 These bits are used to select the clock source for the AD7796/AD7797. Either an on-chip 64 kHz clock or an external clock can be used. The ability to override using an external clock allows several AD7796/ AD7797 devices to be synchronized. In addition, 50 Hz/60 Hz rejection is improved when an accurate external clock drives the AD7796/AD7797 ...
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... Idle Mode. In idle mode, the ADC filter and modulator are held in a reset state although the modulator clocks are still provided Power-Down Mode. In power-down mode, all the AD7796/AD7797 circuitry is powered down, including the burnout currents and CLKOUT circuitry Internal Zero-Scale Calibration. An internal short is automatically connected to the channel. A calibration takes two conversion cycles to complete ...
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... The conversion result from the ADC is stored in this data register. This is a read-only register. On completion of a read operation from this register, the RDY bit/pin is set. ID REGISTER RS2, RS1, RS0 = Power-On/Reset = 0x5A (AD7796)/0x5B (AD7797) The identification number for the AD7796/AD7797 is stored in the ID register. This is a read-only register. CON10 CON9 CON8 ...
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... The analog input channel has an offset register that holds the offset calibration coefficient for the channel. This register is 16 bits wide on the AD7796 and 24 bits wide on the AD7797, and its power-on/reset value is 0x8000(00). The offset register is used in conjunction with the full-scale register to form a register pair. The power-on/reset value is automatically overwritten if an internal or system zero-scale calibration is initiated by the user ...
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... AD7796/AD7797 ADC CIRCUIT INFORMATION OVERVIEW The AD7796/AD7797 are low power ADCs that incorporate a Σ-Δ modulator, in-amp, and an on-chip digital filter intended for measuring wide dynamic range, low frequency signals, such as those in pressure transducers and weigh scales. Each part has one differential input that is buffered. Figure 10 shows the basic connections required to operate the part ...
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... The serial interface can be reset by writing a series the DIN input Logic 1 is written to the AD7796/AD7797 DIN line for at least 32 serial clock cycles, the serial interface is reset. This ensures that the interface can be reset to a known state if the interface gets lost due to a software error or glitch in the system ...
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... AD7796/AD7797 Single Conversion Mode In single conversion mode, the AD7796/AD7797 are placed in shutdown mode between conversions. When a single conver- sion is initiated by setting MD2, MD1, and MD0 in the mode register and 1, respectively, the part powers up, performs a single conversion, and then returns to shutdown mode. The on-chip oscillator requires power-up ...
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... Continuous Read Mode Rather than write to the communication register each time a conversion is complete to access the data, the AD7796/AD7797 can be configured to automatically place the conversions on the DOUT/ RDY line. By writing 01011100 to the communication register, the user need only apply the appropriate number of SCLK cycles to the ADC ...
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... DD therefore, excessive R-C source impedances introduce gain errors. The reference voltage REFIN (REFIN(+) − REFIN(−)) is 2.5 V nominal, but the AD7796/AD7797 are functional with reference voltages 0 excitation (voltage or current) for the transducer on the analog input also drives the reference voltage for the part, the effect of the low frequency noise in the excitation source is removed because the application is ratiometric ...
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... RDY bit in the status register is set, the DOUT/ RDY pin goes low ( low), and the AD7796/AD7797 revert to idle mode. During an internal zero-scale calibration, the zero input is automatically connected internally to the ADC input pins. A ...
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... AD7796/AD7797 are more immune to noise interference than conventional high resolution converters. However, because the resolution of the AD7796/AD7797 is so high, and the noise levels from the AD7796/AD7797 are so low, care must be taken with regard to grounding and layout. The printed circuit board that houses the AD7796/AD7797 should be designed such that the analog and digital sections are separated and confined to certain areas of the board ...
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... WEIGH SCALES Figure 17 shows the AD7796/AD7797 being used in a weigh scale application. The load cell is arranged in a bridge network and gives a differential output voltage between its OUT+ and OUT– ...
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... AD7796BRUZ-REEL –40°C to +85°C 1 AD7797BRUZ –40°C to +85°C 1 AD7797BRUZ-REEL –40°C to +85°C EVAL-AD7796EB EVAL-AD7797EB Pb-free part. ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 5.10 5.00 4. ...