24-Bit, Single-Channel, Ultra Low Power, Sigma Delta A/D Converter
The AD7790/AD7791 are low-power, complete analog front ends for low frequency measurement applications. The device consumes 65 µA of current typically when operated with a 3 V power supply and 75 µA typical when operated with a 5 V power supply with the buffer disabled. The AD7791 contains a 24-bit S-D ADC with one differential input, which can be buffered or unbuffered. The AD7790 is a 16-bit version of the AD7791. The AD7790 has a peak-to-peak resolution of 16 bits at the default output data rate of 16.6 Hz while the AD7789 has a peak to peak resolution of 19 bits, which is equivalent to an effective resolution of 21.5 bits at this output data rate.
The device operates from an internal clock. Therefore, the user does not have to supply a clock source to the device. The output data rate from the part is software programmable, allowing rates from 9.5 Hz to 120 Hz. The p-p resolution from the part varies with the programmed output data rate. With an output data rate of 16.6 Hz, simultaneous 50 Hz/60 Hz rejection is achieved. Power supply monitoring is also included.
The part can be used in single conversion mode whereby the device powers up, performs a single conversion and then returns to powerdown mode. Alternatively, it can be operated in continuous mode. In continuous conversion mode, the part can be configured to continuously read i.e. the conversions are placed on the serial bus automatically as soon as a conversion is complete (the user does not need to write to the ADC to read the data), assuming that the serial clock is applied to the device.
The AD7790/AD7791 is housed in a 10-lead MSOP package.
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Full data on the AD7791 is available in the AD7791 data sheet from Analog Devices, Inc. It is recommended that the AD7791 data sheet be consulted in conjunction with this user guide when using the evaluation board.
The evaluation board interfaces to the USB port of a PC. Software that allows users to easily communicate with the AD7791 is available with the evaluation board.
The AD7791 evaluation board software must be installed before connecting the AD7791 evaluation board to the PC.
Another component on the AD7791 evaluation board is the ADP3303 high precision, low power, 3.3 V output voltage regulator, which powers the USB/serial peripheral interface (SPI).
CN-0216 is a precision weigh scale signal conditioning system. It uses the AD7791, a low power buffered 24-bit sigma-delta ADC along with dual external ADA4528-1 zero-drift amplifiers. This solution allows for high dc gain with a single supply.
This circuit allows great flexibility in designing a custom low-level signal conditioning front end that gives the user the ability to easily optimize the overall transfer function of the combined sensor-amplifier-converter circuit.
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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.