Bootstrap gate-drive supply
Charge budget, droop, recharge and maximum high-side on-time.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Periodic droop: ΔVmax = (Qg + Iq ton) / [C (1 − exp(−toff/RC))]
Assumptions
- Bootstrap capacitor must be entered after DC-bias and tolerance derating. Low-side node is assumed to reach ground during the whole recharge interval.
- 100% high-side duty cannot sustain a conventional bootstrap supply; negative switch-node transients and diode reverse voltage require separate checks.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Driver supply
- 12 V
- Bootstrap diode drop
- 0.7 V
- Minimum high-side supply
- 8 V
- Gate charge per turn-on
- 5e-8 C
- High-side bias plus leakage
- 0.0002 A
- Maximum continuous on-time
- 0.0001 s
- Effective bootstrap capacitance
- 2.2e-7 F
- Total recharge resistance
- 10 Ω
- Available recharge interval
- 0.000005 s
Results
- Single-pulse minimum capacitance
- 2.12121e-8 F
- Periodic worst-case droop
- 0.35473 V
- Charge drawn per pulse
- 7e-8 C
- Single-pulse droop
- 0.318182 V
- Maximum isolated on-time
- 0.00338 s
- Periodic recharge peak
- 0.035473 A
- Average bootstrap diode current
- 0.000666667 A