AD5220

The AD5220 provides a single channel, 128-position digitally controlled variable resistor (VR) device. This device performs the same electronic adjustment function as a potentiometer or variable resistor. These products were optimized for instrument and test equipment push-button applications. A choice between bandwidth or power dissipation are available as a result of the wide selection of end-to-end terminal resistance values.

The AD5220 contains a fixed resistor with a wiper contact that taps the fixed resistor value at a point determined by a digitally controlled UP/DOWN counter. The resistance between the wiper and either end point of the fixed resistor provides a constant resistance step size that is equal to the end-to-end resistance divided by the number of positions (e.g., RSTEP = 10 kW/ 128 = 78 W). The variable resistor offers a true adjustable value of resistance, between the A terminal and the wiper, or the B terminal and the wiper. The fixed A-to-B terminal resistance of 10 kW, 50 kW, or 100 kW has a nominal temperature coefficient of 800 ppm/°C.

The chip select CS, count CLK and U/D direction control inputs of AD5220 set the variable resistor position. These inputs that control the internal UP/DOWN counter can be easily generated with mechanical or push button switches (or other contact closure devices). External debounce circuitry is required for the negative- edge sensitive CLK pin. This simple digital interface eliminates the need for microcontrollers in front panel interface designs.

The AD5220 is available in both surface mount (SO-8) and the 8-lead plastic DIP package. For ultracompact solutions selected models are available in the thin mSOIC package. All parts are guaranteed to operate over the extended industrial temperature range of 40°C to +85°C. For 3-wire, SPI compatible interface applications, see the AD7376/AD8400/AD8402/AD8403 products.