BQ24610EVM: How to choose D1?

Hi Jamie,

  Charge current and output voltage don't matter too much when selecting the bootstrap diode 

For D1 bootstrap diode, choose diode with the following:

• DC blocking voltage rated higher than supply voltage (VCC) with some margin. You want to account for the ringing in your system you would see when HSFET turns on, as when HSFET (Q3) turns on, the bootstrap diode will reverse bias to prevent reverse discharge into REGN. For the EVM, as BQ24610 is rated for 28V input (max recommended operating input voltage), a D1 diode with DC blocking voltage of 40V was used.
• Use sckottky diode
  • Both the diode conduction losses and reverse recovery losses contribute to the total losses in the gate driver and must be considered in calculating the gate driver IC power dissipation.
    • Choose diode with low forward voltage to reduce conduction losses (schottky has lower forward voltage drop)
    • Scottky diodes offer fast recovery time. This means small amount of stored charge can be used for high speed switching applications.
• Peak current through the bootstrap diode is when LSFET is on, and REGN charges the bootstrap capacitor, and is given by Ipeak = Cboot * dV/dt
  • Cboot = 0.1uF
  • dV = 6V (REGN is charging the boostrap capacitor)
  • dt = switching frequency 
  • You can choose a bootstrap diode with forward rating current roughly more than this ideal peak current calculation. D1 uses 480mA forward current rating which is fine.