AD7643 Analog Devices, AD7643 Datasheet
AD7643
Specifications of AD7643
Available stocks
Related parts for AD7643
AD7643 Summary of contents
Page 1
... SAR ADC. 2. Superior Linearity. The AD7643 has no missing 18-bit code. 3. Internal Reference. The AD7643 has a 2.048 V internal reference with a typical drift of ±8 ppm/°C and an on-chip TEMP sensor. 4. Single-Supply Operation. The AD7643 operates from a 2.5 V single supply. 5. Serial or Parallel Interface. ...
Page 2
... Multiplexed Inputs ..................................................................... 17 Driver Amplifier Choice ........................................................... 18 Voltage Reference Input ............................................................ 18 Power Supply............................................................................... 20 Conversion Control ................................................................... 20 Interfaces.......................................................................................... 21 Digital Interface.......................................................................... 21 Parallel Interface......................................................................... 21 Serial interface ............................................................................ 22 Master Serial Interface............................................................... 22 Slave Serial Interface .................................................................. 24 Microprocessor Interfacing....................................................... 26 Application Hints ........................................................................... 27 Layout .......................................................................................... 27 Evaluating the AD7643 Performance ...................................... 27 Outline Dimensions ....................................................................... 28 Ordering Guide .......................................................................... 28 Rev Page ...
Page 3
... AD7643 Unit Bits μA ns MSPS 4 LSB Bits LSB LSB LSB LSB ppm/°C LSB ppm/°C LSB ...
Page 4
... AD7643 Parameter Turn-On Settling Time REFBUFIN Output Voltage REFBUFIN Output Resistance EXTERNAL REFERENCE Voltage Range Current Drain REFERENCE BUFFER REFBUFIN Input Voltage Range REFBUFIN Input Current TEMPERATURE PIN Voltage Output Temperature Sensitivity Output Resistance DIGITAL INPUTS Logic Levels ...
Page 5
... L Rev Page AD7643 , unless otherwise noted. MAX Min Typ Max 800 23 550 1 10 550 250 15 10 500 550 ...
Page 6
... AD7643 Table 4. Serial Clock Timings in Master Read After Convert Mode DIVSCLK[1] DIVSCLK[0] SYNC to SCLK First Edge Delay Minimum Internal SCLK Period Minimum Internal SCLK Period Maximum Internal SCLK High Minimum Internal SCLK Low Minimum SDOUT Valid Setup Time Minimum SDOUT Valid Hold Time Minimum ...
Page 7
... AGND − 0.3 V section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect ±0.3 V device reliability. −0 +2.7 V −0 +3.8 V ±2.8 V −3 +2.8 V −0 +5.5 V ±20 mA 700 mW 2.5 W 125°C –65°C to +125°C Rev Page AD7643 ...
Page 8
... When EXT/INT = high, slave mode. The output data is synchronized to an external clock signal, gated by CS, connected to the SCLK input AGND 1 PIN 1 AVDD IDENTIFIER 2 MODE0 3 MODE1 4 D0/OB/2C 5 AD7643 DGND 6 TOP VIEW DGND 7 (Not to Scale) D1/A0 8 D2/ D4/DIVSCLK[0] 11 D5/DIVSCLK[1] 12 ...
Page 9
... When MODE[1: (serial mode), serial data output. In serial mode, this pin is used as the serial data output synchronized to SCLK. Conversion results are stored in an on-chip register. The AD7643 provides the conversion result, MSB first, from its internal shift register. The data format is determined by the logic level of OB/2C ...
Page 10
... AI Differential Positive Analog Input. 45 TEMP AO Temperature Sensor Analog Output. Normally, 278 mV @ 25°C with a temperature coefficient of 1 mV/°C. This pin can be used to measure the temperature of the AD7643. See the Temperature Sensor section. 46 REFBUFIN AI/O Internal Reference Output/Reference Buffer Input. When PDREF/PDBUF = low, the internal reference and buffer are enabled producing the 1.2 V (typical) band gap output on this pin, which needs external decoupling ...
Page 11
... CNVST input to when the input signal is held for a conversion. Transient Response The time required for the AD7643 to achieve its rated accuracy after a full-scale step function is applied to its input. Reference Voltage Temperature Coefficient It is derived from the typical shift of output voltage at 25° ...
Page 12
... AD7643 TYPICAL PERFORMANCE CHARACTERISTICS 3.0 2.5 2.0 1.5 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –2.5 –3.0 0 65536 131072 CODE Figure 5. Integral Nonlinearity vs. Code 40000 35000 33606 30000 25000 23521 20000 17320 15000 10000 4848 5000 3062 228 0 CODE IN HEX Figure 6. Histogram of 131,072 Conversions Input at the Code Center (External Reference) 2 ...
Page 13
... SNR SINAD ENOB –35 – TEMPERATURE (°C) Figure 15. SNR, SINAD, and ENOB vs. Temperature THD THIRD HARMONIC SECOND HARMONIC –35 – TEMPERATURE (°C) AD7643 600 105 125 120 SFDR 110 100 105 125 ...
Page 14
... AD7643 96.0 95.5 95.0 SNR 94.5 SINAD 94.0 93.5 93.0 –60 –50 –40 –30 INPUT LEVEL (dB) Figure 17. SNR and SINAD vs. Input Level (Referred to Full Scale –55 –35 – TEMPERATURE (°C) Figure 18. Power-Down Operating Currents vs. Temperature –20 –10 0 DVDD OVDD, 3.3V OVDD, 2.5V AVDD 65 85 105 125 Rev ...
Page 15
... V, 3 2.5 V digital logic housed in a Pb-free, 48-lead LQFP package or a tiny 48-lead LFCSP package, which combines space savings with flexibility and allows the AD7643 to be configured as either a serial or a parallel interface. The AD7643 is pin-to-pin compatible with AD7641 ...
Page 16
... AD7643 TRANSFER FUNCTIONS Using the OB/ 2C digital input, except in 18-bit interface mode, the AD7643 offers two output codings: straight binary and twos complement. The LSB size with V = 2.048 × V REF 262,144, which is 15.623 μV. Refer to Figure 22 and Table 8 for the ideal transfer characteristic. ...
Page 17
... MHz, thereby reducing an undesirable aliasing effect and limiting the noise coming from the inputs. Because the input impedance of the AD7643 is very high, the AD7643 can be driven directly by a low impedance source without gain error. To further improve the noise filtering achieved by the AD7643’ ...
Page 18
... SNR by only 0.25 dB when using the RC filter in Figure 23, and by 2.5 dB without it. • The driver needs to have a THD performance suitable to that of the AD7643. Figure 13 gives the THD vs. frequency that the driver should exceed. The AD8021 almost all applications. The compensation capacitor that should have good linearity as an NPO ceramic or mica type ...
Page 19
... V increase the range 2.8 V with an AVDD = 2.7 V. Temperature Sensor The TEMP pin measures the temperature of the AD7643. To improve the calibration accuracy over the temperature range, the output of the TEMP pin is applied to one of the inputs of the analog switch (such as, ADG779), and the ADC itself is used to measure its own temperature ...
Page 20
... OVDD and OGND). CONVERSION CONTROL The AD7643 is controlled by the CNVST input. A falling edge on CNVST is all that is necessary to initiate a conversion. Detailed timing diagrams of the conversion process are shown in Figure 30. Once initiated, it cannot be restarted or aborted, even by the power-down input, PD, until the conversion is complete ...
Page 21
... INTERFACES DIGITAL INTERFACE The AD7643 has a versatile digital interface that can be set up as either a serial or a parallel interface with the host system. The serial interface is multiplexed on the parallel data bus. The AD7643 digital interface also accommodates 2 logic with either OVDD at 2 3.3 V. OVDD defines the logic high output voltage ...
Page 22
... Figure 35. 8-Bit and 16-Bit Parallel Interface SERIAL INTERFACE The AD7643 is configured to use the serial interface when MODE[1: The AD7643 outputs 18 bits of data, MSB first, on the SDOUT pin. This data is synchronized with the 18 clock pulses provided on the SCLK pin. The output data is valid on both the rising and falling edge of the data clock ...
Page 23
... Figure 37. Master Serial Data Timing for Reading (Read Previous Conversion During Convert) INVSCLK = INVSYNC = 0 DIVSCLK[1: RDC/SDIN = D16 RDC/SDIN = 1 INVSCLK = INVSYNC = D16 Rev Page AD7643 ...
Page 24
... Figure 39 and Figure 40 show the detailed timing diagrams of these methods. While the AD7643 is performing a bit decision important that voltage transients be avoided on digital input/output pins or degradation of the conversion result could occur. This is ...
Page 25
... SDOUT X D17 D16 t 16 Figure 40. Slave Serial Data Timing for Reading (Read Previous Conversion During Convert INVSCLK = D15 D1 D0 X15 INVSCLK = D15 D2 D1 Rev Page AD7643 19 20 X17 X16 Y17 Y16 D0 ...
Page 26
... Figure 41 shows an interface diagram between the AD7643 and an SPI-equipped DSP, the ADSP-219x. To accommodate the slower speed of the DSP, the AD7643 acts as a slave device and data must be read after conversion. This mode also allows the daisy-chain feature. The convert command can be initiated in response to an internal timer interrupt ...
Page 27
... Digital and analog ground planes should be joined in only one place, preferably underneath the AD7643 close as possible to the AD7643. If the AD7643 system where multiple devices require analog-to-digital ground connections, the connections should still be made at one point only, a star ground point, established as close as possible to the AD7643 ...
Page 28
... AD7643BCPZ −40°C to +85°C 1 AD7643BCPZRL −40°C to +85°C 1 AD7643BSTZ −40°C to +85°C 1 AD7643BSTZRL −40°C to +85°C 2 EVAL-AD7643CB 3 EVAL-CONTROL BRD3 Pb-free part. 2 This board can be used as a standalone evaluation board or in conjunction with the EVAL-CONTROL BRD3 for evaluation/demonstration purposes. ...