AD7874 Analog Devices, AD7874 Datasheet
AD7874
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AD7874 Summary of contents
Page 1
... Additionally, the aperture delay specification has upper and lower limits allowing multiple AD7874s to sample more than four channels. 3. Fast Microprocessor Interface. The high speed digital interface of the AD7874 allows direct connection to all modern 16-bit microprocessors and digital signal processors. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. ...
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... AD7874–SPECIFICATIONS Parameter A Version B Version S Version Units SAMPLE-AND-HOLD 2 Acquisition Time to 0.01 Droop Rate 1 3 –3 dB Small Signal Bandwidth 500 2 Aperture Delay Aperture Jitter 200 2 Aperture Delay Matching 4 SAMPLE-AND-HOLD AND ADC DYNAMIC PERFORMANCE Signal-to-Noise Ratio 70 Total Harmonic Distortion – ...
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... ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7874 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality ...
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... TOP VIEW CLK 8 (Not to Scale DB11 (MSB) 10 DB10 11 11 DB9 12 DB8 13 DGND 14 LCCC CONVST AD7874 CS 7 TOP VIEW 8 CLK (Not to Scale DB11 (MSB) 11 DB10 –4– IN4 27 V IN3 REF OUT ...
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... A. The nominal reference voltage for correct operation of the AD7874 Voltage Reference Output. The internal 3 V analog reference is provided at this pin. To oper- ate the AD7874 with internal reference, REF OUT is connected to REF IN. The external load capability of the reference is 500 A. Negative Supply Voltage, – ...
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... REF OUT channel digitized. ANALOG INPUT The analog input of Channel 1 of the AD7874 is as shown in Figure 4. The analog input range into an input resis- tance of typically The designed code transitions occur midway between successive integer LSB values (i.e., 1/2 LSB, 3/2 LSBs, 5/2 LSBs – ...
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... The sequence in which the channel conversions takes place is automatically taken care of by the AD7874. This means that the user does not have to provide address lines to the AD7874 or worry about selecting which channel digitized. Reading data from the device consists of four read operations to the same microprocessor address ...
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... SNR data can be ob- tained. Figure 8 shows a typical 2048 point FFT plot of the AD7874BN with an input signal of 10 kHz and a sampling frequency of 29 kHz. The SNR obtained from this graph is 73.2 dB. It should be noted that the harmonics are taken into account when calculating the SNR ...
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... Fig- ure 11. This shows very good integral linearity performance nfb where from the AD7874 at an input frequency of 10 kHz. The absence of large spikes in the plot shows good differential linearity. Sim- plified versions of the formulae used are outlined below. ...
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... CS initiated with a timer and the processor is interrupted when the conversion sequence is completed. The TMS320C25 does not have a separate RD output to drive the AD7874 RD input di- AD7874* rectly. This has to be generated from the processor STRB and R/W outputs with the addition of some logic gates. The RD sig- ...
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... Unlike the previous interface examples, the microprocessor initiates conversion. This is achieved by gating the 8086 WR signal with a decoded address output (different to the AD7874 CS address). The AD7874 INT line is used to in- terrupt the microprocessor when the conversion sequence is completed. Data is read from the AD7874 using the following ...
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... AD7874. Rotor information is obtained by measuring the voltage from two of the inputs to the motor. Channel 3 and Channel 4 of the AD7874 are used to obtain this information. Once again the relative phase of the two channels is important. A DSP microprocessor is used to perform the mathematical transformations and control loop calculations on the information fed back by the AD7874 ...
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... The analog supplies are labeled V+ and V– and the range for both supplies (see silkscreen in Figure 23). Connection to the 5 V digital supply is made via SKT8. The +5 V supply and the –5 V supply required by the AD7874 are generated from voltage regulators (IC3 and IC4) on the V+ and V– supplies. ...
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... AD7874 LK1 SKT1 LK2 SKT2 LK3 SKT3 LK4 SKT4 V– Figure 20. Data Acquisition Circuit Using the AD7874 IC3 CONVST 78L05 SKT6 IC1 V AD713 CONVST IN1 DB11 DB0 V INT IN2 CS V IC2 IN3 AD7874 ...
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... Figure 22. PCB Component Side Layout for the Circuit of Figure 20 Figure 23. PCB Solder Side Layout for the Circuit of Figure 20 REV. C –15– AD7874 ...
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... Connects the analog inputs to the buffer amplifi- ers. The analog inputs may also be connected to a component grid for signal conditioning. LK5 Selects either the AD7874 internal clock or an ex- ternal clock source. LK6 Selects either the AD7874 internal reference or an external reference source. ...