Feedback Resistor Calculator

Name: DC/DC Feedback Resistor Calculator
Availability: InStock
Author: Oleg Serbinov

About: This calculator helps you determine optimal feedback resistor values (R1 and R2) for DC/DC converter circuits. The feedback network creates a voltage divider that sets the output voltage according to the formula: V_out = V_ref × (1 + R1/R2). Choose from automatic selection with standard resistor values, specify one known resistor, or manually enter both values.

Reference Voltage (Vref/FB)

Vref Tolerance (%)

Output Voltage

Resistor Series

PPM for R1 (upper)

PPM

PPM for R2 (lower)

PPM

Auto Selection

One Resistor

Manual Input

Resistor Range

kΩ

Known Resistor

Resistor Value

kΩ

R1 (upper)

kΩ

R2 (lower)

kΩ

Resistor Specifications & Package Info

SMD Packages:

                        0201: 50mW/15V (max. 50V)

                        0402: 62.5mW/50V (max. 100V)

                        0603: 100mW/50V (max. 100V)

                        0805: 125mW/150V (max. 200V)

                        1206: 250mW/200V (max. 400V)

                        1210: 500mW/200V (max. 400V)

                        2010: 750mW/200V (max. 400V)

                        2512: 1W/200V (max. 400V)

Through-hole Packages:

                        1/4W: 250mW/500V (Axial Ø2.3×6mm)

                        1/2W: 500mW/500V (Axial Ø3.2×9mm)

                        1W: 1W/500V (Axial Ø3.6×10mm)

                        2W: 2W/500V (Axial Ø5×12mm)

                        5W: 5W/500V (Axial Ø7×16mm)

DC/DC Design Guidelines

Resistor Values: Lower values (1kΩ-10kΩ) improve noise immunity but increase quiescent current, reducing light-load efficiency. Higher values (100kΩ+) improve efficiency but are susceptible to PCB leakage and noise coupling.
Feedforward Capacitor (C_ff): Often added in parallel with R1 to improve phase margin and transient response. Typical values range from 10pF to 100pF depending on the crossover frequency.
Layout (PCB): Place R1 and R2 as close to the FB pin as possible. Keep the FB trace very short to minimize noise pickup, and route it away from the switch node (SW) and inductor.

⚡ Safety Factor: Calculator recommends 2.5x power margin for reliability

*Working voltage/Maximum voltage ratings based on industry standards

Custom Electronics Design & Development

Transforming complex concepts into market-ready products with precision engineering.

🔄 Full-Cycle R&D: Comprehensive support from feasibility studies and prototyping to mass production scaling.
📐 Circuit Design & Simulation: Reliable schematic capture tailored to cost and performance requirements.
🟩 Advanced PCB Layout: High-density interconnect (HDI) and multi-layer designs optimized for Signal Integrity and EMC/EMI compliance.
📋 Design for Manufacturing (DFM): Production-ready documentation, including Gerber files, pick-and-place data, and cost-optimized BOMs.
💻 Embedded Firmware Development: Efficient C/C++ firmware for STM32, ESP32, and other architectures (Bare-metal & RTOS).
🔧 Mechanical Engineering (SolidWorks): 3D CAD modeling, thermal management, and custom enclosure design for seamless ECAD/MCAD integration.

📧 serbinovoleg@gmail.com

🌐 Website GitHub

Developed by Oleg Serbinov

v1.0 • 2025-12-30