AD7747 Analog Devices, AD7747 Datasheet
AD7747
Specifications of AD7747
Available stocks
Related parts for AD7747
AD7747 Summary of contents
Page 1
... The architecture features inherent high resolution (24-bit no missing codes 19.5-bit effective resolution), high linearity (±0.01%), and high accuracy (±10 fF factory calibrated). The AD7747 capacitance input range is ±8 pF (changing), and it can accept common-mode capacitance (not changing), which can be balanced by a program- mable on-chip digital-to-capacitance converter (CAPDAC) ...
Page 2
... ESD Caution.................................................................................. 6 Pin Configuration and Function Descriptions............................. 7 Typical Performance Characteristics ............................................. 8 Output Noise and Resolution Specifications .............................. 11 Serial Interface ................................................................................ 12 Read Operation........................................................................... 12 Write Operation.......................................................................... 12 AD7747 Reset.............................................................................. 13 General Call................................................................................. 13 Register Descriptions ..................................................................... 14 Status Register ............................................................................. 15 Cap Data Register....................................................................... 15 VT Data Register ........................................................................ 15 Cap Setup Register ..................................................................... 16 VT Setup Register....................................................................... 16 EXC Setup Register ...
Page 3
... Conversion time = 62 ms, see Table 6 and Table 7 μV rms Conversion time = 62 ms, see Table 6 and Table 7 μV nV/° ppm of FS/°C Internal reference ppm of FS/°C External reference nA/V pA/V/°C dB Internal reference External reference AD7747 4 /2 REF /2 REF ...
Page 4
... AD7747 Parameter 5 Normal Mode Rejection 2 Common-Mode Rejection INTERNAL VOLTAGE REFERENCE Voltage Drift vs. Temperature EXTERNAL VOLTAGE REFERENCE INPUT 2 Differential REFIN Voltage 2 Absolute REFIN Voltage Average REFIN Input Current Average REFIN Input Current Drift Common-Mode Rejection SERIAL INTERFACE LOGIC INPUTS (SCL, SDA) V Input High Voltage ...
Page 5
... Rev Page −40°C to +125°C, unless otherwise noted. DD Unit Test Conditions/Comments See Figure 2 kHz μs μs μs μs μs After this period, the first clock is generated μs Relevant for repeated start condition μs μs μs μs t HD;STA t t SU;STA SU;STO S AD7747 P ...
Page 6
... AD7747 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 3. Parameter Positive Supply Voltage V to GND DD Voltage on any Input or Output Pin to GND ESD Rating (ESD Association Human Body Model, S5.1) Operating Temperature Range Storage Temperature Range Junction Temperature TSSOP Package θ JA (Thermal Impedance-to-Air) TSSOP Package θ ...
Page 7
... SCL SDA 1 16 RDY SHLD VDD 3 14 AD7747 TST GND 4 13 TOP VIEW REFIN(+) VIN(– (Not to Scale) REFIN(–) VIN(+) 6 11 CIN1(– CIN1(+) CONNECT Figure 3. Pin Configuration Rev Page AD7747 ...
Page 8
... AD7747 TYPICAL PERFORMANCE CHARACTERISTICS –20 –40 –60 –80 –8 –7 –6 –5 –4 –3 –2 – INPUT CAPACITANCE (pF) Figure 4. Capacitance Input Integral Nonlinearity CAPDAC = 0x3F DD 2000 1000 0 –1000 –2000 –3000 –50 – TEMPERATURE (ºC) Figure 5. Capacitance Input Gain Drift vs. Temperature; ...
Page 9
... SERIAL RESISTANCE (kΩ) Figure 14. Capacitance Input Error vs. Serial Resistance; CIN(+) to GND = 8 pF and 25pF 0.2 0 –0.2 –0.4 –0.6 2.5 3.0 3.5 4.0 4.5 VDD (V) Figure 15. Capacitance Input Power Supply Rejection (PSR); CIN(+) to GND = 8 pF AD7747 100 8 pF 100 5.0 5.5 ...
Page 10
... AD7747 200 150 100 50 0 –50 –100 –150 –200 CAPDAC CODE Figure 16. CAPDAC Differential Nonlinearity (DNL) 2.0 1.5 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –50 – TEMPERATURE (°C) Figure 17. Internal Temperature Sensor Error vs. Temperature 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –2.5 –3.0 –50 –25 ...
Page 11
... OUTPUT NOISE AND RESOLUTION SPECIFICATIONS The AD7747 resolution is limited by noise. The noise performance varies with the selected conversion time. Table 5 shows typical noise performance and resolution for the capacitive channel. These numbers were generated from 1000 data samples acquired in continuous conversion mode excitation of 16 kHz, ± ...
Page 12
... In this case, the AD7747 becomes a slave transmitter. In all instances, the AD7747 acts as a standard slave device on the I The start byte address for the AD7747 is 0x90 for a write and 0x91 for a read. READ OPERATION When a read is selected in the start byte, the register that is currently addressed by the address pointer is transmitted on to the SDA line by the AD7747 ...
Page 13
... To reset the AD7747 without having to reset the entire I an explicit reset command is provided. This uses a particular address pointer word as a command word to reset the part and upload all default settings. The AD7747 does not respond to the bus commands (do not acknowledge) during the default values upload for approximately 150 μ ...
Page 14
... AD7747 REGISTER DESCRIPTIONS The master can write to or read from all of the AD7747 registers except the address pointer register, which is a write-only register. The address pointer register determines which register the next read or write operation accesses. All communications with the part through the bus start with an access to the address pointer register ...
Page 15
... For the temperature sensor, the temperature can be calculated from code using the following equation: Temperature (°C) = (Code/2048) − 4096 Rev Page Bit 3 Bit 2 Bit 1 – RDY RDYVT REF AD7747 Bit 0 RDYCAP 1 ), REF ). ...
Page 16
... AD7747 CAP SETUP REGISTER Address Pointer 0x07, Default Value 0x00 Capacitive channel setup. Table 11. Cap Setup Register Bit Map Bit Bit 7 Mnemonic CAPEN Default 0 Table 12. Bit Mnemonic Description 7 CAPEN CAPEN = 1 enables capacitive channel for single conversion, continuous conversion, or calibration. 6 – This bit must be 0 for proper operation. ...
Page 17
... EXCLVL0 Voltage on Cap 0 ± ± ±V × 3 ± Rev Page Bit 3 Bit 2 Bit 1 EXCDAC EXCEN EXCLVL1 EXC Low Level EXC High Level V × 3/8 V × 5 × 1/4 V × 3 × 1/8 V × 7 AD7747 Bit 0 EXCLVL0 1 ...
Page 18
... AD7747 CONFIGURATION REGISTER Address Pointer 0x0A, Default Value 0xA0 Converter update rate and mode of operation setup. Table 17. Configuration Register Bit Map Bit Bit 7 Mnemonic VTFS1 Default 0 Table 18. Bit Mnemonic Description 7 VTFS1 Voltage/temperature channel digital filter setup—conversion time/update rate setup. 6 VTFS0 ...
Page 19
... DACB value, Code 0x00 ≈ 0 pF, Code 0x3F ≈ full range DACB Bit 6 Bit 5 Bit 4 – 0 Bit 6 Bit 5 Bit 4 – 0 Rev Page Bit 3 Bit 2 Bit 1 DACA—6-Bit Value 0x00 Bit 3 Bit 2 Bit 1 DACB—6-Bit Value 0x00 AD7747 Bit 0 Bit 0 ...
Page 20
... AD7747 CAP OFFSET CALIBRATION REGISTER 16 Bits, Address Pointer 0x0D, 0x0E, Default Value 0x8000 The capacitive offset calibration register holds the capacitive channel zero-scale calibration coefficient. The coefficient is used to digitally remove the capacitive channel offset. The register value is updated automatically following the execution of a capacitance offset calibration. The capacitive offset calibra- tion resolution (cap offset register LSB) is less than 32 aF ...
Page 21
... SHLD pins, and any capacitance between these pins does not affect the CIN charge transfer. Ideally, the CIN to SHLD capacitance does not have any contribution to the AD7747 result. To get the best result, locate the AD7747 as close as possible to 2 C-compatible serial the capacitive sensor ...
Page 22
... The AD7747 can be used for interfacing to a single-ended capacitive sensor. In this configuration the sensor should be connected to one of the AD7747 CIN pins, for example CIN(+) and the other pin should be left open circuit. Note that the CAPDIFF bit in the Cap Setup register must be set all times for the correct operation ...
Page 23
... See Figure 14 in the Typical Performance Characteristics section. between active shield CAPACITIVE GAIN CALIBRATION The AD7747 gain is factory calibrated for the full scale of ±8.192 pF in the production for each part individually. The factory gain coefficient is stored in a one-time programmable /C ...
Page 24
... The Σ-Δ ADC converts the ΔV factory calibration coefficients. Thus, the output code is proportional to temperature. The AD7747 has a low power consumption resulting in only a small effect due to the part self-heating (less than 0.5° V). ...
Page 25
... REF REFIN(–) Figure 38. Resistive Temperature Sensor Connected to the Voltage Input The AD7747 Σ-Δ core can work as a high resolution ( ENOB) classic ADC with a fully differential voltage input. The ADC can be used either with the on-chip high precision, low drift, 1.17 V voltage reference, or with an external reference connected to the fully differential reference input pins ...
Page 26
... TYPICAL APPLICATION DIAGRAM TEMP SENSOR VIN (+) VIN (–) CIN1(+) CIN1(–) SHLD EXCITATION Figure 39. Basic Application Diagram for a Differential Capacitive Sensor 0.1µF VDD CLOCK AD7747 GENERATOR 24-BIT Σ-Δ DIGITAL MUX GENERATOR FILTER INTERFACE CONTROL LOGIC CALIBRATION VOLTAGE CAP DAC 1 REFERENCE ...
Page 27
... BSC 4. PIN 1 1.20 MAX 0.20 0.09 8° 0.30 0.65 0° 0.19 SEATING BSC PLANE COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-153-AB Figure 40. 16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16) Dimensions shown in millimeters Package Description 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP Evaluation Board Rev Page AD7747 0.75 0.60 0.45 Package Option RU-16 RU-16 RU-16 ...
Page 28
... AD7747 NOTES Purchase of licensed components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I Rights to use these components system, provided that the system conforms to the I ©2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners ...