ad670低成本信号调理8位ADC

　　The AD670 is a complete 8-bit signal conditioning analogto-digital converter. It consists of an instrumentation amplifier front end along with a DAC， comparator， successive approximation register （SAR）， precision voltage reference， and a threestate output buffer on a single monolithic chip. No external components or user trims are required to interface， with full accuracy， an analog system to an 8-bit data bus. The AD670 will operate on the +5 V system supply. The input stage provides differential inputs with excellent common-mode rejection and allows direct interface to a variety of transducers. The device is configured with input scaling resistors to permit two input ranges： 0 mV to 255 mV （1 mV/LSB） and 0 to 2.55 V （10 mV/LSB）。 The AD670 can be configured for both unipolar and bipolar inputs over these ranges. The differential inputs and common-mode rejection of this front end are useful in applications such as conversion of transducer signals superimposed on common-mode voltages. The AD670 incorporates advanced circuit design and proven processing technology. The successive approximation function is implemented with I2 L （integrated injection logic）。 Thin-film SiCr resistors provide the stability required to prevent missing codes over the entire operating temperature range while laser wafer trimming of the resistor ladder permits calibration of the device to within ±1 LSB. Thus， no user trims for gain or offset are required. Conversion time of the device is 10 µs. The AD670 is available in four package types and five grades. The J and K grades are specified over 0°C to +70°C and come in 20-pin plastic DIP packages or 20-terminal PLCC packages. The A and B grades （–40°C to +85°C） and the S grade （–55°C to +125°C） come in 20-pin ceramic DIP packages.