8.1 Adjustable Output Voltage Calculations

To calculate the resistor divider values for the MCP16367/8/9, Equation 8-1 can be used. R_TOP is connected to V_OUT, R_BOT is connected to GND, and both are connected to the FB input pin.

Equation 8-1. Resistor Divider Values

R_{T O P} = R_{B O T} \times (\frac{V_{O U T}}{V_{F B}} - 1)

3.3V Output Example


V_{OUT_target}	=	3.3V
V_FB	=	0.8V
R_BOT	=	10 kΩ
R_TOP	=	31.25 kΩ  (Standard Value = 31.6 kΩ)

The gain of the transconductance error amplifier is determined by its internal impedance, and the external resistor divider does not affect the system gain. Therefore, a wide range of resistor values can be used for the feedback network. It is recommended to use feedback resistors with 1% tolerance or better for improved accuracy. To enhance efficiency at light loads, larger resistor values are preferred; however, excessively high values may increase susceptibility to noise.