The AD5222 provides a dual-channel, 128-bit digitally controlled variable resistance (VR) device. This device performs the same electronic adjustment function as a potentiometer or variable resistor. These products are optimized for instrumentation and test equipment button applications. The choice between bandwidth or power dissipation is available as a choice of terminal-to-terminal termination resistor values. The AD5222 contains two fixed resistors in contact with the wiper, tap a number to determine the fixed resistance value at a point to control the up/down counter. The resistance between the wiper and the end point is either a fixed resistance providing a constant resistance step equal to the end-to-end resistance divided by the number of positions (eg, RSTEP = 10 kW/128 = 78 W). A variable resistor provides true adjustable value resistance, between terminal A and the wiper, or terminal B wiper. Fixed B terminal 10 kW resistance, 50 kW, 100 kW, 1 MW nominal temperature coefficient -35 PPM/°C. Chip select CS, count CLK and U/D direction control inputs set the variable resistor position. The mode determines whether the two village representatives are incremented together or separately. Relative setting between wipers that changes as the wipers are incremented UP or DOWN in logic zero mode. Also, the relative proportions between the wipers can be preserved if the wipers reach the end of the resistor array. In standalone mode (logic 1) only the VR determined by the DACSEL pin changes. DACSEL (logic 0) changes RDAC 1. These inputs, which control the internal up/down counters, can be easily generated with mechanical or push button switches (or other contact closure devices). This simple digital interface eliminates the need for a microcontroller designed for front panel interface. The AD5222 is available in a surface mount (SO-14) package. For ultra-small solutions, select models in the ultra-thin TSSOP-14 package. All components are guaranteed to operate over the extended industrial temperature range of -40°C to +85°C. For applications with a 3-wire SPI compatible interface, see AD5203/AD5204/AD5206, AD7376, AD8400/AD8402/AD8403 products.