JAJSER7D November 2018 – January 2019 LMG1210
PRODUCTION DATA.
The bootstrap diode blocks the high voltage from the gate drive circuitry when the switch node swings high, with the rated blocking voltage equal to the maximum Vds of the GaN FET. For low or moderate frequency operation ultra-fast recovery diodes (<50 ns) are recommended. The internal low voltage switch in the LMG1210 acts to reduce the reverse recovery. For high-frequency operation a Schottky diode is recommended. To minimize switching losses and improve performance, it is important to select a diode with low capacitance.
For extreme cases, where the low-side FET on time is less than 20 ns, TI recommends using a small GaN FET as synchronous bootstrap instead of a diode. In this case, TI recommends leaving the BST pin floating or connected to VDD, and to connect the source of the synchronous bootstrap directly to VDD.