AD7798 Analog Devices, AD7798 Datasheet
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AD7798
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AD7798 Summary of contents
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... Hz to 470 Hz. The part operates with a power supply from 2 5.25 V. The AD7798 consumes a current of 300 μA typical, whereas the AD7799 consumes 380 μA typical. Both devices are housed in a 16-lead TSSOP package. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. ...
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... Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Timing Characteristics..................................................................... 6 Absolute Maximum Ratings............................................................ 8 ESD Caution.................................................................................. 8 Pin Configuration and Function Descriptions............................. 9 Output Noise and Resolution Specifications .............................. 10 AD7798 ........................................................................................ 10 AD7799 ........................................................................................ 11 Typical Performance Characteristics ........................................... 12 On-Chip Registers .......................................................................... 13 Communication Register .......................................................... 13 Status Register ............................................................................. 14 Mode Register ............................................................................. 14 Configuration Register .............................................................. 16 Data Register ............................................................................... 17 ID Register ...
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... Rev Page AD7798/AD7799 to T MIN MAX Test Conditions/Comments AD7799: f < 242 Hz ADC AD7798 See Table 5 to Table 8 See Table 5 to Table 8 AIN = 1 V/gain, gain ≥ REFIN(+) – REFIN(–), gain = 1 to 128 REF Gain = Gain = Gain = 4 to 128 V = (AIN(+) + AIN(− ...
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... Output High Voltage Output Low Voltage Output High Voltage Output Low Voltage Floating-State Leakage Current Floating-State Output Capacitance Data Output Coding 1 AD7798B/AD7799B Unit 2.5 V nom 0.1 V min AV V max DD GND − min max DD 400 nA/V typ ± ...
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... Buffered mode, gain = 130 μA typ @ AV 165 μA typ @ AD7798: gain = 4 to 128, 300 μA typ @ AV 350 μA typ @ AD7799: gain = 4 to 128, 380 μA typ @ AV 440 μA typ @ − ...
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... AD7798/AD7799 TIMING CHARACTERISTICS 5.25 V, GND = 0 V, Input Logic Input Logic Table Parameter Limit MIN MAX t 100 3 t 100 4 Read Operation Write Operation ...
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... CS ( MSB DOUT/RDY ( 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 AD7798/AD7799 LSB LSB ...
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... AD7798/AD7799 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 3. Parameter Rating AV to GND −0 GND −0 Analog Input Voltage to GND −0 Reference Input Voltage to GND −0 Digital Input Voltage to GND −0 Digital Output Voltage to GND − ...
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... AIN2(– REFIN(+) Figure 5. Pin Configuration and GND + 0.1 V. The nominal reference voltage (REFIN(+) – REFIN(−)) is 2.5 V, but the part − 0 voltage is independent of the voltage Rev Page AD7798/AD7799 and GND DD and GND DD ; therefore, AV can equal ...
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... V. Table 6 shows the effective resolution, and the output peak-to-peak resolution is shown in parentheses important to note that Table 5. Output RMS Noise (μV) vs. Gain and Output Update Rate for the AD7798 Using a 2.5 V Reference Update Rate Gain of 1 Gain ...
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... Rev Page AD7798/AD7799 Gain of 32 Gain of 64 Gain of 128 0.035 0.027 0.027 0.048 0.037 0.040 0.085 0.065 0.065 0.118 0.097 0.094 0.178 0.133 0.134 0.265 0.192 0.192 0.476 0.326 ...
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... AD7798/AD7799 TYPICAL PERFORMANCE CHARACTERISTICS 8388640 8388630 8388620 8388610 8388600 8388590 8388580 0 200 400 SAMPLES Figure 6. AD7799 Noise ( /2, Gain = 64, Update Rate = 4.17 Hz) REF CODE Figure 7. AD7799 Noise Distribution Histogram (V Gain = 64, Update Rate = 4.17 Hz) 8388680 8388660 8388640 8388620 8388600 8388580 8388560 ...
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... IO register Offset register Full-scale register CR4 CR3 CR2 RS1(0) RS0(0) CREAD(0) Rev Page AD7798/AD7799 CR1 CR0 0(0) 0(0) Register Size 8 bits 8 bits 16 bits 16 bits 16 bits (AD7798)/24 bits (AD7799) 8 bits 8 bits 16 bits (AD7798)/24 bits (AD7799) 16 bits (AD7798)/24 bits (AD7799) ...
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... Bit Name Description MR15 to MR13 MD2 to MD0 Mode Select Bits. These bits select the operational mode of the AD7798/AD7799 (see Table 13). MR12 PSW Power Switch Control Bit. Set by user to close the power switch PSW to GND. The power switch can sink mA. Cleared by user to open the power switch. When the ADC is placed in power-down mode, the power switch is opened ...
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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 this mode, all AD7798/AD7799 circuitry is powered down, including the burnout currents Internal Zero-Scale Calibration. An internal short is automatically connected to the enabled channel. A calibration takes two conversion cycles to complete ...
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... AD7798/AD7799 CONFIGURATION REGISTER RS2, RS1, RS0 = Power-On/Reset = 0x0710 The configuration register is a 16-bit register from which data can be read or to which data can be written. This register is used to configure the ADC for unipolar or bipolar mode, to enable or disable the buffer, to enable or disable the burnout currents, to select the gain, and to select the analog input channel ...
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... Each analog input channel has a dedicated offset register that holds the offset calibration coefficient for the channel. This register is 16 bits wide on the AD7798 and 24 bits wide on the AD7799, and its power-on/reset value is 8000(00) hex. The offset register is used in conjunction with its associated 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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... IN+ OUT– OUT+ IN– OVERVIEW The AD7798/AD7799 are low power ADCs that each incorporate a ∑-Δ modulator, a buffer, an in-amp, and on-chip digital filtering intended for the measurement of wide dynamic range, low frequency signals, such as those in pressure transducers and weigh scales. Each part has three differential inputs that can be buffered or unbuffered ...
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... The serial interface can be reset by writing a series the DIN input Logic 1 is written to the AD7798/AD7799 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 is lost due to a software error or a glitch in the system ...
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... DIN DOUT/RDY SCLK Continuous-Conversion Mode This is the default power-up mode. The AD7798/AD7799 continuously converts, with the RDY bit in the status register going low each time a conversion is complete low, the DOUT/ RDY line also goes low when a conversion is complete. To read a conversion, the user can write to the communication register, indicating that the next operation is a read of the data ...
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... If the user does not read the conversion before the completion of the next conversion insufficient serial clocks are applied to the AD7798/AD7799 to read the word, the serial output register is reset when the next conversion is complete, and the new conversion is placed in the output serial register ...
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... AD7799, which is equivalent to 25.5 bits effective resolution bits peak-to-peak resolution when V The AD7798/AD7799 can be programmed to have a gain 16, 32, 64, or 128 using Bit G2 to Bit G0 in the configuration register. Therefore, with a 2.5 V reference, the unipolar ranges are from ( 19.53 mV 2.5 V), and the bipolar ranges are from ± ...
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... REFIN(–) inputs are open circuit, the AD7798/AD7799 detect that there is no longer a valid reference. In this case, the NOREF bit of the status register is set the AD7798/AD7799 are performing normal conversions and the NOREF bit becomes active, the conversion results revert to all 1s. Therefore not necessary to continuously monitor the status of the NOREF bit when performing conversions ...
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... MD0 bits in the mode register. After the calibration is complete, the contents of the corresponding calibration registers are updated, the RDY bit in the status register is set, the DOUT/ RDY pin goes low ( low), and the AD7798/AD7799 revert to idle mode. During an internal zero-scale or full-scale calibration, the respective zero-scale and full-scale input are automatically connected internally to the ADC input pins ...
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... AD7798/AD7799 are more immune to noise interference than conventional high resolution converters. However, because the resolution of the AD7798/AD7799 is so high and the noise levels from the AD7798/AD7799 are so low, care must be taken with regard to grounding and layout. The printed circuit board that houses the AD7798/AD7799 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 19 shows the AD7798/AD7799 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– terminals. Assuming excitation voltage, the full- scale output range from the transducer when the sensitivity is 2 mV/V ...
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... PLANE COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-153-AB Figure 20. 16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16) Dimensions shown in millimeters Package Description 16-Lead TSSOP 16-Lead TSSOP Evaluation Board 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP Evaluation Board Rev Page AD7798/AD7799 0.75 0.60 0.45 Package Option RU-16 RU-16 RU-16 RU-16 RU-16 RU-16 ...
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... AD7798/AD7799 NOTES ©2005–2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04856-0-3/07(A) Rev Page ...