AD7745 Analog Devices, AD7745 Datasheet
AD7745
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AD7745 Summary of contents
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... The AD7745 has one capacitance input channel, while the AD7746 has two channels. Each channel can be configured as single-ended or differential. The AD7745/AD7746 are designed for floating capacitive sensors. For capacitive sensors with one plate connected to ground, the AD7747 is recommended ...
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... Absolute Maximum Ratings............................................................ 6 Pin Configurations and Function Descriptions ........................... 7 Typical Performance Characteristics ............................................. 8 Output Noise and Resolution Specifications .............................. 11 Serial Interface ................................................................................ 12 Read Operation........................................................................... 12 Write Operation.......................................................................... 12 AD7745/AD7746 Reset ............................................................. 13 General Call................................................................................. 13 Register Descriptions ..................................................................... 14 Status Register ............................................................................. 15 Cap Data Register....................................................................... 15 VT Data Register ........................................................................ 15 Cap Set-Up Register ................................................................... 16 VT Set-Up Register .................................................................... 16 EXC Set-Up Register ...
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... REF GND − 0. 0.03 DD ±3 ± ±3 15 0.025 0.1 Rev. 0| Page AD7745/AD7746 Unit Test Conditions/Comments 1 pF Factory calibrated % of FSR Bit Conversion time ≥ Bit Conversion time = 62 ms, see Table 5 Bit Conversion time = 62 ms, see Table 5 See Table 5 aF/√Hz ...
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... AD7745/AD7746 Parameter Full-Scale Drift vs. Temperature Average VIN Input Current Analog VIN Input Current Drift Power Supply Rejection Power Supply Rejection Normal Mode Rejection Common-Mode Rejection INTERNAL VOLTAGE REFERENCE Voltage Drift vs. Temperature EXTERNAL VOLTAGE REFERENCE INPUT 2 Differential REFIN Voltage 2 Absolute REFIN Voltage ...
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... BUF HIGH t t HD:DAT SU:DAT Figure 3. Serial Interface Timing Diagram Rev. 0| Page AD7745/AD7746 ; –40°C to +125°C, unless otherwise noted. DD Unit Test Conditions/Comments See Figure 3 kHz µs µs µs µs µs After this period, the first clock is generated µ ...
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... AD7745/AD7746 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 (Thermal Impedance-to-Air) TSSOP Package θ ...
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... REFIN(– CIN1(– CIN1(+) CONNECT Figure 4. AD7745 Pin Configuration (16-Lead TSSOP) Table 4. Pin Function Descriptions Pin No. Mnemonic Description 1 SCL Serial Interface Clock Input. Connects to the master clock line. Requires pull-up resistor if not already provided in the system. 2 RDY Logic Output ...
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... AD7745/AD7746 TYPICAL PERFORMANCE CHARACTERISTICS 100 –5 –4 –3 –2 – INPUT CAPACITANCE (pF) Figure 6. Capacitance Input Integral Nonlinearity the Same Configuration as in Figure 31 DD 2000 1000 0 –1000 –2000 –3000 –50 – TEMPERATURE (°C) Figure 7. Capacitance Input Offset Drift vs. Temperature, ...
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... Figure 16. Capacitance Input Power Supply Rejection (PSR), CIN(+) to EXC = 4 pF, the Same Configuration as in Figure 30 0.20 0.15 0.10 0.05 0 –0.05 –0.10 –0.15 –0.20 10000 100000 0 Figure 17. CAPDAC Differential Nonlinearity (DNL) Rev. 0| Page AD7745/AD7746 SERIAL RESISTANCE (kΩ the Same Configuration as in Figure 34. 3.0 3.5 4.0 4.5 5.0 ...
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... AD7745/AD7746 2.0 1.5 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –50 – TEMPERATURE (°C) Figure 18. Internal Temperature Sensor Error vs. Temperature 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 –2.5 –3.0 –50 – TEMPERATURE (°C) Figure 19. External Temperature Sensor Error vs. Temperature 0 –20 –40 –60 –80 –100 –120 0 100 200 ...
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... OUTPUT NOISE AND RESOLUTION SPECIFICATIONS The AD7745/AD7746 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 32 kHz, ± ...
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... SDA line for transmission to the master acknowledge is received, the AD7745/AD7746 return to the idle state and the address pointer is not incremented. The address pointers’ auto-incrementer allow block data to be written or read from the starting address and subsequent incremental addresses ...
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... Hence, a master wanting to retain control of the bus issues successive start conditions known as repeated start conditions. AD7745/AD7746 RESET To reset the AD7745/AD7746 without having to reset the entire bus, 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 ...
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... R/W 1 The CIN2 bit is relevant only for AD7746. The CIN2 bit should always the AD7745. accessed over the bus and a read/write operation is selected, the address pointer register is set up. The address pointer register determines from or to which register the operation takes place. ...
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... To prevent losing some of the results, the VT DATA register should be read before the next conversion on the voltage/ temperature channel is finished. For the temperature sensor, the temperature can be calculated from code using the following equation: Temperature (°C) = (Code/2048) − 4096 Rev. 0| Page AD7745/AD7746 Bit 3 Bit 2 Bit 1 EXCERR RDY RDYVT ...
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... AD7745/AD7746 CAP SET-UP REGISTER Address Pointer 0x07, Default Value 0x00 Capacitive channel setup. Table 11. CAP Set-Up 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 CIN2 CIN2 = 1 switches the internal multiplexer to the second capacitive input on the AD7746. ...
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... Description 7 CLKCTRL The CLKCTRL bit should be set to 0 for the specified AD7745/AD7746 performance. CLKCTRL = 1 decreases the excitation signal frequency and the modulator clock frequency by factor of 2. This also increases the conversion time on all channels (capacitive, voltage, and temperature factor of 2. ...
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... AD7745/AD7746 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 VTF1 Default 0 Table 18. Bit Mnemonic Description 7 VTF1 Voltage/temperature channel digital filter setup—conversion time/update rate setup. 6 VTF0 The conversion times in this table are valid for the CLKCTRL = 0 in the EXC SETUP register ...
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... On the AD7746, the register is shared by the two capacitive channels. VOLT GAIN CALIBRATION REGISTER 16 Bits, Address Pointer 0x11,0x12, Default Value 0xXXXX Voltage gain calibration register. The register holds the voltage channel full-scale factory calibration coefficient. Rev. 0| Page AD7745/AD7746 Bit 3 Bit 2 Bit 1 0x00 Bit 3 Bit 2 Bit 1 DACB— ...
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... I C-compatible serial interface. The AD7745 has one capacitive input, while the AD7746 has two capacitive inputs. All other features and specifications are identical for both parts. CAPACITANCE-TO-DIGITAL CONVERTER Figure 28 shows the CDC simplified functional diagram. The ...
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... AD7746 before executing conversion on a different channel. SINGLE-ENDED CAPACITIVE INPUT When configured for a single-ended mode (the CAPDIFF bit in the Cap Setup register is set to 0), the AD7745/AD7746 CIN(–) pin is disconnected internally. The CDC (without using the CAPDACs) can measure only positive input capacitance in the range (see Figure 30) ...
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... DATA ± 4pF CDC 0x000000 ... 0xFFFFFF The AD7745/AD7746 CDC result would be affected by a leak- DATA age current from the C isolated from the ground. The influence of the leakage current varies with the power supply voltage. The following limits can be used as a guideline for the allowed leakage current or the ...
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... CIN EXC Figure 39. Parasitic Serial Resistance The AD7745/AD7746 CDC result is affected by a resistance in series with the measured capacitance. The total serial resistance, which refers Figure 39, should be less than 1 kΩ for the specified performance. See typical performance charac- teristics shown in Figure 15 ...
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... AND Figure 42. Resistive Temperature Sensor Connected to the Voltage Input SCALING The AD7745/AD7746 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 external reference connected to the fully differential reference input pins ...
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... SEATING BSC PLANE COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-153-AB Figure 44. 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 16-Lead TSSOP 16-Lead TSSOP 16-Lead TSSOP Evaluation Board Rev Page AD7745/AD7746 0.75 0.60 0.45 Package Option RU-16 RU-16 RU-16 RU-16 RU-16 RU-16 ...
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... AD7745/AD7746 NOTES Rev Page ...
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... NOTES Rev Page AD7745/AD7746 ...
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... AD7745/AD7746 NOTES 2 Purchase of licensed I C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I 2 Patent Rights to use these components system, provided that the system conforms to the I © 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners ...