Regardless of the method of charging the bootstrap capacitor, the TPS7H60x3-SP requires an external bootstrap diode rated to withstand the input voltage that is applied to the converter power stage in the half-bridge configuration. Care must be taken when selecting the external bootstrap diode. The bootstrap diode needs to be capable of handling peak transient currents that occur during the startup period. Fast recovery diodes should be used in the bootstrap circuit. The user needs to examine the I-V characteristics of the selected diode to verify that the forward voltage under the intended operating conditions does not become too large to trigger the undervoltage lockout of the BP5H regulator. Overall, the user needs to meet the conditions of Equation 5:

where:

• VIN is the gate driver input voltage
• n is the number of external bootstrap diodes placed in series
• V_F is the forward voltage drop of the bootstrap diode
• V_{BOOT_UVLO} is the falling undervoltage lockout threshold of BOOT (6.65 V typical)