V_ref V

V_out V

Ra kΩ

Rb kΩ

This tool is suitable for feedback-based adjustable step-up and step-down DC-DC ICs and LDOs. Currently supported chips:

DC-DC: FP6291LR-G1, SY8088AAC, MPQ4430, LM2576-ADJ, LM2596-ADJ, MC33063, MC34063, MP1584, XL4001, SX1308;

LDO: TPS730x, TPS7A30x, TPS7A47x, TPS7A49x, TPS7A70x series (e.g., TPS7A4901DGNR); MIC2915X/30X/50X/75X series (e.g., MIC29302WU-TR); and AP2127K-ADJ, SPX3819M5x, etc.

If it is not one of the above models, please check the datasheet to determine if it is applicable. Also, note that different chips have different requirements for the range of voltage divider resistor values. Feedback on the compatibility status of unknown models is welcome.

Instructions:

Enter reference voltage first, then fill in any two of output voltage, top resistor (Ra) or bottom resistor (Rb); the remaining parameter will be calculated instantly along with the circuit diagram, formula and step-by-step details.

For example, when using SY8088IAAC, to calculate the voltage divider feedback resistor combination for a 3.3V output:

Vref = 0.6, Vout = 3.3, Ra (R_H) and Rb (R_L) range from 100 kΩ to 1 MΩ. First, try the median value Ra = 470 kΩ, resulting in Rb = 104.44 kΩ;
The current Rb value does not have a suitable standard resistor. Since it is close to the lower limit of the recommended range, the value should be adjusted upwards. Try adjusting Ra to 680 kΩ, resulting in Rb = 151.11 kΩ;
Adjust Rb to a standard 150 kΩ resistor, and finally determine the voltage divider feedback resistor combination of 680 kΩ/150 kΩ, with an output voltage of 3.32 V.

* The reference voltage Vref (Vfb, FB) and the range of dividing resistor values should be determined by consulting the device datasheet.

This calculator is based on the formula: Vout = Vref * (1 + Ra / Rb), which can also be written as Vout = (Ra + Rb) / Rb * Vfb. For more information, click to view details.