Many applications using a DC/DC regulator are implemented with a resistor divider in the feedback path to set up Vout. However, for some high end applications, the voltage needs to be adjusted in order to optimize the application’s performance. A Digitally Controlled Potentiometer (DCP) can be used in both high end and low end applications to provide this flexibility.
The typical Buck DC/DC converter scheme includes a PWM driver, switches, inductor, filter, and feedback divider. The feedback voltage, FB, from the resistor divider R1 and R2, is a negative input for the error amplifier of the voltage control loop. In addition to the point of load regulation, the feedback divider also sets up the desired output voltage, Vout. The minimum output voltage can be set as low as Vref, according to Equation 1. The maximum output is also determined by the resistor divider ratio, as well as input voltage and the maximum duty cycle. The reference voltage, Vref, can be obtained from a PWM controller datasheet.