The AD7709 is a complete analog front end for low frequency measurement applications. It contains a 16-bit :- ADC， selectable reference inputs， three switchable matched excitation current sources， low-side power switches， and a digital I/O port. The 16-bit channel with PGA accepts fully differential， unipolar， and bipolar input signal ranges from 1.024 REFIN/128 to 1.024 REFIN. It can be configured as two fully differential input channels or four pseudo-differential input channels. Signals can be converted directly from a transducer without the need for signal conditioning. The device operates from a 32.768 kHz crystal with an on-chip PLL generating the required internal operating frequency. The output data rate from the part is software programmable. The p-p resolution from the part varies with the programmed gain and output data rate. The part operates from a single 3 V or 5 V supply. When operating from 3 V supplies， the power dissipation for the part is 3.75 mW. The AD7709 is housed in a 24-lead TSSOP package.