AD7795 Analog Devices, AD7795 Datasheet
AD7795
Specifications of AD7795
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AD7795 Summary of contents
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... The output data rate from each part can vary from 4. 470 Hz. Both parts operate with a power supply from 2 5.25 V. The B-grade parts (AD7794 and AD7795) are specified for a temperature range of −40°C to +105°C while the C-grade part (AD7794) is specified for a temperature range of −40°C to +125° ...
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... B to Rev. C Updated Format..................................................................Universal Added AD7794 C-Grade Part...........................................Universal Changes to Specifications ................................................................ 3 Changes to Ordering Guide .......................................................... 36 6/06—Rev Rev. B Added AD7795 ...................................................................Universal Changes to Features.......................................................................... 1 Changes to Table 1............................................................................ 3 Changes to RMS Noise and Resolution Specifications Section..................................................................... 12 Changes to Table 19........................................................................ 20 Changes to ADC Circuit Information Section ........................... 25 Changes to Ordering Guide ...
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... Rev Page AD7794/AD7795 unless otherwise noted. MIN MAX Test Conditions/Comments Settling time = 2/output update rate f ≤ 242 Hz ADC See the RMS Noise and Resolution Specifications section See the RMS Noise and Resolution Specifications section ...
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... Common-Mode Voltage Analog Input Current Buffered Mode or In-Amp Active 2 Average Input Current AD7794B/AD7795B AD7794C Average Input Current Drift Unbuffered Mode Average Input Current Average Input Current Drift AD7794/AD7795 Unit 100 dB min 100 dB min 100 dB min 97 dB min 97 dB min 97 dB min 4 ...
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... V max DD GND − min Rev Page AD7794/AD7795 Test Conditions/Comments 70 dB typ, 50 ± 1 Hz, 60 ± 1 Hz, FS[3:0] = 1010 90 dB typ, 50 ± 1 Hz, FS[3:0] = 1001 100 dB typ, 60 ± 1 Hz, FS[3:0] = 1000 70 dB typ, 50 ± 1 Hz, 60 ± 1 Hz, FS[3:0] = 1010 100 dB typ, 50 ± 1 Hz, FS[3:0] = 1001 100 dB typ, 60 ± ...
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... T T AD7794C V (+) T V (− (+) to V (− (+) T V (− (+) to V (− Input Currents Input Capacitance AD7794/AD7795 Unit nom DD ms/nF typ ±2 °C typ 0.81 mV/°C typ 7 Ω max 9 Ω max 30 mA max AV − 0.6 V min DD 0.4 V max 4 V min 0.4 V max 64 ± ...
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... 350 μA typ @ AV DD gain = 4 to 128, external reference 400 μA typ @ 450 μA typ @ AV DD gain = 4 to 128, internal reference AD7794B, AD7795B AD7794C = 4 V, gain = 25°C ...
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... AD7794/AD7795 TIMING CHARACTERISTICS 5.25 V, GND = 0 V, Input Logic Input Logic Table 2. Parameter 1, 2 Limit MIN MAX t 100 3 t 100 4 Read Operation Write Operation ...
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... TIMING DIAGRAMS DOUT/RDY ( MSB SCLK ( INPUT OUTPUT Figure 3. Read Cycle Timing Diagram CS ( SCLK ( DIN (I) MSB I = INPUT OUTPUT Figure 4. Write Cycle Timing Diagram Rev Page AD7794/AD7795 LSB LSB ...
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... AD7794/AD7795 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 to GND AIN/Digital Input Current Operating Temperature Range B Grade C Grade Storage Temperature Range ...
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... CONNECT Figure 5. Pin Configuration and GND + 0.1 V. The nominal reference voltage, (REFIN1(+) − REFIN1(−)), is DD and GND + 0.1 V. The nominal reference voltage (REFIN2(+) to REFIN2(−)) is 2.5 V, but the part Rev Page AD7794/AD7795 and GND. DD and GND − 0 ...
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... AD7794/AD7795 Pin No. Mnemonic Description 18 AIN4(−)/REFIN2(−) Analog Input/Negative Reference Input. AIN4(−) is the negative terminal of the differential analog input pair AIN4(+)/AIN4(−). This pin also functions as the negative reference input for REFIN2. This reference input can lie anywhere between GND and AV ...
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... Table 7. Effective Resolution (Bits) vs. Gain and Output Update Rate for the AD7795 Using an External 2.5 V Reference with Chop Enabled Update Rate (Hz) Gain of 1 Gain of 2 4.17 16 (16) 16 (16) 8.33 16 (16) 16 (16) 16.7 16 (16) 16 (16) 33.2 16 (16) 16 (16) 62 ...
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... Table 10. Effective Resolution (Bits) vs. Gain and Output Update Rate for the AD7795 Using an Internal 1.17 V Reference with Chop Enabled Update Rate (Hz) Gain of 1 Gain of 2 4.17 16 (16) 16 (16) 8.33 16 (16) 16 (16) 16.7 16 (16) 16 (16) 33.2 16 (16) 16 (16) ...
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... Table 13. Effective Resolution (Bits) vs. Gain and Output Update Rate for the AD7795 Using an Internal 1.17 V Reference with Chop Disabled Update Rate (Hz) Gain of 1 Gain of 2 4.17 16 (16) 16 (16) 8.33 16 (16) 16 (16) 16.7 16 (16) 16 (16) 33.2 16 (16) 16 (16 (16) 16 (15 ...
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... AD7794/AD7795 TYPICAL PERFORMANCE CHARACTERISTICS 8388800 8388750 8388700 8388650 8388600 8388550 8388500 8388450 0 200 400 600 READING NUMBER Figure 6. Typical Noise Plot for the AD7794 (Internal Reference, Gain = 64, Update Rate = 16.7 Hz, Chop Enabled 8388482 8388520 8388560 8388600 8388640 CODE Figure 7 ...
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... The number in brackets indicates the power-on/reset default status of that bit. CR4 CR3 CR2 RS1(0) RS0(0) CREAD(0) Rev Page AD7794/AD7795 CR1 CR0 0(0) 0(0) Register Size 8-bit 8-bit 16-bit 16-bit 24-bit (AD7794)/16-Bit (AD7795) 8-bit 8-bit 24-bit (AD7794)/16-Bit (AD7795) 24-bit (AD7794)/16-Bit (AD7795) ...
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... The ERR bit is also set if the voltage applied to the selected reference input is invalid. SR4 0 This bit is automatically cleared. SR3 0/1 This bit is automatically cleared on the AD7795 and is automatically set on the AD7794. SR2 to CH2 to CH0 These bits indicate which channel is being converted by the ADC. SR0 Table 16 outlines the bit designations for the status register. SR0 through SR7 indicate the bit locations, with SR denoting that the bits are in the status register ...
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... MR7 to MR6 CLK1 to CLK0 These bits are used to select the clock source for the AD7794/AD7795. Either the on-chip 64 kHz clock can be used or an external clock can be used. The ability to use an external clock allows several AD7794/AD7795 devices to be synchronized. Also, 50 Hz/60 Hz rejection is improved when an accurate external clock drives the AD7794/AD7795 ...
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... 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 AD7794/AD7795 circuitry is powered down including the current sources, power switch, burnout currents, bias voltage generator, and clock circuitry Internal Zero-Scale Calibration. ...
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... Hz only) 120 80 dB (50 Hz only) 120 65 dB (50 Hz and 60 Hz) 160 66 dB (50 Hz and 60 Hz) 200 69 dB (50 Hz and 60 Hz) 240 70 dB (50 Hz and 60 Hz) 320 72 dB (50 Hz and 60 Hz) 480 74 dB (50 Hz and 60 Hz) Rev Page AD7794/AD7795 ...
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... AD7794/AD7795 CONFIGURATION REGISTER RS2, RS1, RS0 = Power-On/Reset = 0x0710 The configuration register is a 16-bit read/write register that is used to configure the ADC for unipolar or bipolar mode, enable or disable the buffer, enable or disable the burnout currents, select the gain, and select the analog input channel. ...
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... AIN1(−)/AIN1(− Reserved Reserved Reserved Reserved Reserved Reserved Rev Page AD7794/AD7795 Calibration Pair Automatically selects the internal 1.17 V reference and sets the gain to 1 Automatically selects the internal 1.17 V reference and sets the gain to 1/6 0 ...
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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 = 0xXF The identification number for the AD7794/AD7795 is stored in the ID register. This is a read-only register. IO7 IO6 IO5 ...
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... OFFSET REGISTER RS2, RS1, RS0 = Power-On/Reset = 0x8000 (AD7795), 0x800000 (AD7794)) The offset register is a 16-bit register on the AD7795 and a 24-bit register on the AD7794. The offset register holds the offset calibration coefficient for the ADC and its power-on reset value is 0x8000/0x800000, for the AD7794/AD7795, respectively ...
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... AD7794/AD7795 ADC CIRCUIT INFORMATION OVERVIEW The AD7794/AD7795 are low power ADCs that incorporate a ∑-Δ modulator, buffer, reference, in-amp, and on-chip digital filtering, which are intended for the measurement of wide dynamic range, low frequency signals (such as those in pressure transducers), weigh scales, and temperature measurement applications ...
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... Figure 17. Filter Response with Update Rate = 4.17 Hz (Chop Disabled) 0 –20 –40 –60 –80 –100 2500 3000 0 Figure 18. Filter Response with Update Rate = 16.7 Hz (Chop Disabled) Rev Page AD7794/AD7795 1000 2000 3000 4000 5000 6000 7000 8000 9000 FREQUENCY (Hz ...
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... The serial interface can be reset by writing a series the DIN input Logic 1 is written to the AD7794/AD7795 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 some glitch in the system ...
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... CS 0x08 DIN DOUT/RDY SCLK CS DIN DOUT/RDY SCLK CS 0x5C DIN DOUT/RDY SCLK 0x200A Figure 21. Single Conversion 0x58 DATA Figure 22. Continuous Conversion DATA Figure 23. Continuous Read Rev Page AD7794/AD7795 0x58 DATA 0x58 DATA DATA DATA ...
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... If the user has not read the conversion before the completion of the next conversion insufficient serial clocks are applied to the AD7794/AD7795 to read the word, the serial output register is reset when the next conversion is complete. The new conversion is then placed in the output serial register. ...
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... Each AD7794/AD7795 can be programmed to have a gain 16, 32, 64, and 128 using Bit G2 to Bit G0 in the configuration register. Therefore, with an external 2.5 V reference, the unipolar ranges are from 2.5 V and the bipolar ranges are from ± ...
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... IOUT1 or IOUT2, along with selecting the value of the current. These current sources can be used to excite external resistive bridge or RTD sensors. BIAS VOLTAGE GENERATOR A bias voltage generator is included on the AD7794/AD7795. It biases the negative terminal of the selected input channel to AV /2. This function is available on inputs AIN1(− AIN3(− ...
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... NOXREF bit when performing conversions only necessary to verify its status if the conversion result read from the ADC data register is all 1s. If the AD7794/AD7795 are performing either offset or full-scale calibrations and the NOXREF bit becomes active, the updating of the respective ...
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... AGND sections of the layout. The ground plane of the AD7794/AD7795 should be allowed to run under the AD7794/AD7795 to prevent noise coupling. The power supply lines to the AD7794/AD7795 should use as wide a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. Fast switching signals, such as clocks, should be shielded with digital ground to avoid radiating noise to other sections of the board ...
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... OUT+ IN– second advantage of using the AD7794/AD7795 in transducer- based applications is that the low-side power switch can be fully utilized in low power applications. The low-side power switch is connected in series with the cold side of the bridges. In normal operation, the switch is closed and measurements can be taken. ...
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... AD7794CRUZ-REEL –40°C to +125°C 1 AD7795BRUZ –40°C to +105°C 1 AD7795BRUZ-REEL –40°C to +105°C EVAL-AD7794EB EVAL-AD7795EB RoHS Compliant Part. ©2004-2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 7.90 7.80 7. 4.50 4 ...