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 transconductance error amplifier gain is controlled by its internal impedance. The external divider resistors have no effect on system gain, so a wide range of values can be used. It is recommended to use feedback resistors with 1% tolerances or better. To improve the efficiency at light load, using large value resistors is recommended. However, if the values are too high, the regulator will be more susceptible to noise.