AD7691 Analog Devices, AD7691 Datasheet
AD7691
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AD7691 Summary of contents
Page 1
... SDI input, to daisy-chain several ADCs on a single 3-wire bus and provides an optional busy indicator compatible with 1 logic, using the separate VIO supply. The AD7691 is housed in a 10-lead MSOP or a 10-lead QFN (LFCSP) with operation specified from −40°C to +85°C. 196608 262144 One Technology Way, P ...
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... CS Mode, 3-Wire with Busy Indicator .................................... 19 CS Mode, 4-Wire Without Busy Indicator ............................. 20 CS Mode, 4-Wire with Busy Indicator .................................... 21 Chain Mode Without Busy Indicator ...................................... 22 Chain Mode with Busy Indicator ............................................. 23 Application Hints ........................................................................... 24 Layout .......................................................................................... 24 Evaluating the AD7691 Performance ...................................... 24 Outline Dimensions ....................................................................... 25 Ordering Guide .......................................................................... 25 Rev Page ...
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... V IN REF kHz 100 IN REF kHz 2 REF of 250 kSPS, followed by postdigital filtering with an output word rate f S Rev Page AD7691 , unless otherwise noted. Typ Max Unit Bits +V V REF REF V + 0.1 V REF /2 − 0 ...
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... AD7691 VDD = 2 5.25 V, VIO = 2 VDD, V Table 3. Parameter Conditions/Comments REFERENCE Voltage Range Load Current 250 kSPS, REF = 5 V SAMPLING DYNAMICS −3 dB Input Bandwidth Aperture Delay VDD = 5 V DIGITAL INPUTS Logic Levels DIGITAL OUTPUTS Data Format Serial 18-bit, twos complement ...
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... CYC t CNVH t SCK t SCK t SCKL t SCKH t HSDO t DSDO DIS t SSDICNV t HSDICNV t SSCKCNV t HSCKCNV t SSDISCK t HSDISCK t DSDOSDI Rev Page AD7691 1 , unless otherwise noted. Min Typ Max 0.5 2.2 1 Unit μ ...
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... AD7691 VDD = 2 4.5 V, VIO = 2 VDD, V Table 5. Parameter Conversion Time: CNV Rising Edge to Data Available Acquisition Time Time Between Conversions CNV Pulse Width (CS Mode) SCK Period (CS Mode) SCK Period (Chain Mode) VIO Above 3 V VIO Above 2.7 V VIO Above 2.3 V SCK Low Time ...
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... THERMAL RESISTANCE θ is specified for the worst-case conditions, that is, a device JA soldered in a circuit board for surface-mount packages. Table 7. Thermal Resistance Package Type 10-Lead MSOP 10-Lead QFN (LFCSP) ESD CAUTION Rev Page AD7691 θ θ Unit JA JC 200 44 °C/W 43.4 6.5 °C/W ...
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... SDO CNV /2 and must be driven 180° out of phase with IN−. REF /2 and must be driven 180° out of phase with IN+. REF Rev Page REF 1 10 VIO VDD 2 9 SDI AD7691 IN SCK TOP VIEW IN– SDO (Not to Scale) GND 5 6 ...
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... VDD = REF = 2.5V – 180kSPS 2kHz IN –40 SNR = 96.4dB THD = –120.3dB 2ND HARMONIC = –132.5dB –60 3RD HARMONIC = –121.2dB –80 –100 –120 –140 –160 –180 FREQUENCY (kHz) Figure 12. 2 kHz FFT Plot, 2.5 V AD7691 262144 910 ...
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... AD7691 104 102 100 2.3 2.6 2.9 3.2 3.5 3.8 4.1 REFERENCE VOLTAGE (V) Figure 13. SNR, SINAD, and ENOB vs. Reference Voltage 105 REF 100 V = 2.5V REF –55 –35 – TEMPERATURE (°C) Figure 14. SNR vs. Temperature 105 V = 5V, –10dB REF 100 2.5V, –1dB REF 85 80 ...
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... Figure 22. Zero Error, Gain Error vs. Temperature VDD + VIO –35 – TEMPERATURE (°C) Figure 23. Power-Down Current vs. Temperature VDD = 5V, 85°C VDD = 5V, 25° 100 SDO CAPACITIVE LOAD (pF) Delay vs. Capacitance Load and Supply DSDO AD7691 125 105 125 120 ...
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... AD7691 100 FREQUENCY (kHz) Figure 25. PSSR vs. Frequency 1000 10000 Rev Page REF 1 10 100 1000 FREQUENCY (kHz) Figure 26. Analog Input CMRR vs. Frequency = VDD = 5V 10000 ...
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... CNV input and when the input signal is held for a conversion. Transient Response Transient response is the time required for the ADC to acquire its input accurately after a full-scale step function is applied. Rev Page AD7691 N (2 /Peak-to-Peak Noise ...
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... The AD7691 provides the user with an on-chip track-and-hold and does not exhibit pipeline delay or latency, making it ideal for multiple multiplexed channel applications. The AD7691 is specified from 2 5.25 V and can be interfaced to any 1 digital logic family housed in a 10-lead MSOP or a tiny 10-lead QFN (LFCSP) that combines space savings and allows flexible configurations ...
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... TYPICAL CONNECTION DIAGRAM Figure 29 shows an example of the recommended connection diagram for the AD7691 when multiple supplies are available REF 3 ADA4841-2 V– REF 3 ADA4841-2 V– 1 SEE VOLTAGE REFERENCE INPUT SECTION FOR REFERENCE SELECTION USUALLY A 10µF CERAMIC CAPACITOR (X5R). ...
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... For ac applications, the driver should have a THD performance commensurate with the AD7691. For multichannel multiplexed applications, the driver amplifier and the AD7691 analog input circuit must settle for a full- scale step onto the capacitor array at an 18-bit level (0.0004%, 4 ppm). In the amplifier’s data sheet, settling at ...
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... POWER SUPPLY The AD7691 uses two power supply pins: a core supply (VDD) and a digital input/output interface supply (VIO). VIO allows direct interface with any logic between 1.8 V and VDD. To reduce the supplies needed, the VIO and VDD pins can be tied together. The AD7691 is independent of power supply sequencing between VIO and VDD ...
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... AD7691 CS MODE, 3-WIRE WITHOUT BUSY INDICATOR This mode is usually used when a single AD7691 is connected to an SPI-compatible digital host. The connection diagram is shown in Figure 35, and the corresponding timing is given in Figure 36. With SDI tied to VIO, a rising edge on CNV initiates a conversion, selects the CS mode, and forces SDO to high impedance ...
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... CS MODE, 3-WIRE WITH BUSY INDICATOR This mode is usually used when a single AD7691 is connected to an SPI-compatible digital host having an interrupt input. The connection diagram is shown in Figure 37, and the corresponding timing is given in Figure 38. With SDI tied to VIO, a rising edge on CNV initiates a conversion, selects the CS mode, and forces SDO to high impedance ...
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... Although the rising edge can be used to capture the data, a digital host using the SCK falling edge allows a faster reading rate, provided it has an acceptable hold time. After the 18 falling edge, or when SDI goes high, whichever occurs first, SDO returns to high impedance and another AD7691 can be read. CNV CNV AD7691 ...
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... CS MODE, 4-WIRE WITH BUSY INDICATOR This mode is normally used when a single AD7691 is connected to an SPI-compatible digital host with an interrupt input, and it is desired to keep CNV, which is used to sample the analog input, independent of the signal used to select the data reading. This requirement is particularly important in applications where low jitter on CNV is desired ...
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... SDO B readback. When the conversion is complete, the MSB is output onto SDO and the AD7691 enters the acquisition phase and powers down. The remaining data bits stored in the internal shift register are clocked by subsequent SCK falling edges. For each ADC, SDI feeds the input of the internal shift register and is clocked by the SCK falling edge. Each ADC in the chain outputs its data MSB first, and 18 × ...
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... D C completed their conversions, the SDO pin of the ADC closest to the digital host (see the AD7691 ADC labeled C in Figure 45) is driven high. This transition on SDO can be used as a busy indicator to trigger the data readback controlled by the digital host. The AD7691 then enters the acquisition phase and powers down ...
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... Avoid running digital lines under the device because this couples noise onto the die unless a ground plane under the AD7691 is used as a shield. Fast switching signals, such as CNV or clocks, should not run near analog signal paths. Crossover of digital and analog signals should be avoided ...
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... AD7691BCPZRL –40°C to +85°C AD7691BCPZRL7 –40°C to +85°C AD7691BRMZ –40°C to +85°C AD7691BRMZ-RL7 –40°C to +85°C EVAL-AD7691CBZ EVAL-CONTROL BRD2Z 2 2 EVAL-CONTROL BRD3Z RoHS Compliant Part. 2 These boards allow control and communicate with all Analog Devices evaluation boards ending in the CB designators. ...
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... AD7691 NOTES Rev Page ...
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... NOTES Rev Page AD7691 ...
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... AD7691 NOTES ©2006–2011 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06146-0-7/11(B) Rev Page ...