The AD7787 is a low power， complete analog front end for low frequency measurement applications. It contains a low noise 24-bit Σ-Δ ADC with one differential input and one singleended input that can be buffered or unbuffered. 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 and can be varied from 9.5 Hz to 120 Hz， with the rms noise equal to 1.1 μV at the lower update rate. The internal clock frequency can be divided by a factor of 2， 4， or 8， which leads to a reduction in the current consumption. The update rate， cutoff frequency， and settling time scales with the clock frequency. The part operates with a power supply from 2.5 V to 5.25 V. When operating from a 3 V supply， the power dissipation for the part is 225 μW maximum. It is housed in a 10-lead MSOP.