AD7791 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.

Features and Benefits

Power
Supply: 2.5 V to 5.25 V operation
Normal: 75 µA maximum
Power-down: 1 µA maximum
RMS noise: 1.1 µV at 9.5 Hz update rate
19.5-bit p-p resolution (22 bits effective resolution)
Integral nonlinearity: 3.5 ppm typical

Simultaneous 50 Hz and 60 Hz rejection
Internal clock oscillator
Rail-to-rail input buffer
VDD monitor channel
Temperature range: –40°C to +105°C
10-lead MSOP

Data Sheets

Document	note
AD7791: Low Power, Buffered 24-Bit Sigma-Delta ADC Data Sheet (Rev. A)	PDF 308 kB

Application Notes

Document	note
AN-202: An IC Amplifier User’s Guide to Decoupling, Grounding, and Making Things Go Right for a Change (Rev. B)	PDF 76.97 K
AN-968: Current Sources: Options and Circuits (Rev. 0)	PDF 131 kB
AN-311: How to Reliably Protect CMOS Circuits Against Power Supply Overvoltaging	PDF 217 kB
AN-607: Selecting a Low Bandwidth (<15 kSPS) Sigma-Delta ADC (Rev. E)	PDF 222 kB
AN-615: Peak-to-Peak Resolution Versus Effective Resolution (Rev. 0)	PDF 70 kB
AN-397: Electrically Induced Damage to Standard Linear Integrated Circuits:	PDF 149 kB