# High-Side Driver Bootstrap Calculator

## Frequently Asked Questions

*Note: The calculator is provided as a guideline only. The utility is not meant to be exhaustive nor provide a calculation for every possible scenario.*

## Determine Power Switch Gate Charge

As you enter the parametric data, the calculator highlights the component being entered and describes the parameter. You may change parameters at any time, and the calculator will respond with the correct results.

- Select the MOSFET or IGBT to be used in the end application. Find the VGS versus QG gate charge for the chosen MOSFET or IGBT.
- Pick an operating point from this curve, and enter this value into the QG box of the calculator.
- Enter the remaining system parameters (minimum and maximum duty cycle, driver quiescent current, etc.) — the calculator will return the bootstrap capacitor value, worst-case recharge current and average current through the bootstrap diode.

## Parameters to Enter

- Number of MOSFETS or IGBTs in parallel (#)
- System modulation frequency (Hz)
- Maximum and minimum duty cycle (%)
- Driver output-side quiescent current from driver data sheet (mA)
- Driver output side voltage (V)
- Percent bootstrap cap ripple voltage as a percentage of VDDO (%)

## Parameters Returned

- Bootstrap capacitor total gate charge (nC)
- Bootstrap capacitor value (nF)
- Maximum bootstrap capacitor recharge current at maximum duty cycle (mA)