GENERAL DESCRIPTION

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 on chip 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.

The AD7705/AD7706 devices, with a 3 V supply and a 1.225 V reference, can handle unipolar input signal ranges of 0 mV to 10 mV through 0 V to 1.225 V. The devices can accept bipolar input ranges of ±10 mV through ±1.225 V. Therefore, the AD7705/AD7706 devices perform all signal conditioning and conversion for a 2-channel or 3-channel system.

The AD7705/AD7706 are ideal for use in smart, microcontroller, or DSP-based systems. The devices feature a serial interface that can be configured for 3-wire operation. Gain settings, signal polarity, and update rate selection can be configured in software using the input serial port. The parts contains self-calibration and system calibration options to eliminate gain and offset errors on the part itself or in the system. CMOS construction ensures very low power dissipation, and the power-down mode reduces the standby power consumption to 20 μW typ.

These parts are available in a 16-lead, wide body (0.3 inch), plastic dual in-line package (DIP); a 16-lead, wide body (0.3 inch), standard small outline (SOIC) package; and a low profile, 16-lead, thin shrink small outline package (TSSOP).

FEATURES

AD7705: 2 fully differential input channel ADCs

AD7706: 3 pseudo differential input channel ADCs

16 bits no missing codes

0.003 nonlinearity

Programmable gain front end: gains from 1 to 128

3-wire serial interface

SPI?-, QSPI?-, MICROWIRE?-, and DSP-compatible

Schmitt-trigger input on SCLK

Ability to buffer the analog input

2.7 V to 3.3 V or 4.75 V to 5.25 V operation

Power dissipation 1 mW maximum @ 3 V

Standby current 8 μA maximum

16-lead PDIP, 16-lead SOIC, and 16-lead TSSOP packages

AD7706BR屬于集成電路（IC） > 模數(shù)轉(zhuǎn)換器（ADC）。亞德諾半導(dǎo)體技術(shù)有限公司制造生產(chǎn)的AD7706BR模數(shù)轉(zhuǎn)換器（ADC）模數(shù)轉(zhuǎn)換器（ADC、A/D 或 A 轉(zhuǎn) D）對模擬信號(hào)進(jìn)行采樣，例如由麥克風(fēng)采集的聲音或傳感器的輸出，然后將其轉(zhuǎn)換為數(shù)字信號(hào)。一般來說，數(shù)字輸出是二進(jìn)制補(bǔ)碼二進(jìn)制數(shù)，與輸入成比例。輸入類型可能是差分、偽差分或單端輸入。模數(shù)轉(zhuǎn)換器可按照位數(shù)、采樣率、輸入數(shù)、接口、轉(zhuǎn)換器數(shù)和架構(gòu)（例如自適應(yīng)增量、雙斜率、折疊、流水線、SAR、三角積分、兩步式）進(jìn)行選擇。