AD7705_7706

　　The AD7705/AD7706 are complete analog front ends for low

　　frequency measurement applications. These 2-/3-channel devices

　　can accept low level input signals directly from a transducer and

　　produce serial digital output. The devices employ a Σ-Δ

　　conversion technique to realize up to 16 bits of no missing codes

　　performance. The selected input signal is applied to a

　　proprietary， programmable-gain front end based around an

　　analog modulator. The modulator output is processed by an onchip digital filter. The first notch of this digital filter can be programmed via an on-chip control register， allowing adjustment of

　　the filter cutoff and output update rate.

　　The AD7705/AD7706 devices operate from a single 2.7 V to

　　3.3 V or 4.75 V to 5.25 V supply. The AD7705 features two fully

　　differential analog input channels; the AD7706 features three

　　pseudo differential input channels.

　　Both devices feature a differential reference input. Input signal

　　ranges of 0 mV to 20 mV through 0 V to 2.5 V can be

　　incorporated on both devices when operating with a VDD of 5 V

　　and a reference of 2.5 V. They can also handle bipolar input

　　signal ranges of ±20 mV through ±2.5 V， which are referenced to

　　the AIN（−） inputs on the AD7705 and to the COMMON input

　　on the AD7706.