"ad872" - 1 õppematerjal

Book Analog Interfacing to Embedded Microprocessors

Other common input voltage ranges are ±2.5v and ±3v. With the trend toward lower-powered devices and small consumer equip- ment, the trend in ADC devices is to lower voltage, single-supply operation. Traditional single-supply ADCs have operated from +5V and had an input range between 0v and 5v. Newer parts often operate at 3.3 or 2.7v, and have an input range somewhere between 0v and the supply. Internal Reference Many ADCs provide an internal reference voltage. The Analog Devices AD872 is a typical device with an internal 2.5v reference. The internal reference voltage is brought out to a pin and the reference input to the device is also connected to a pin. To use the internal reference, the two pins are connected together. To use your own external reference, connect it to the reference input instead of the internal reference. Reference Bypassing Although the reference input is usually high impedance, with low DC current