APEC Unveils New 100V GaN Half-Bridge Driver

Analog Devices has recently unveiled a stand-alone 100V half-bridge driver designed specifically for GaN power hemts. This innovative driver boasts a propagation delay of just 10ns and delay matching of 1.5ns between the top and bottom channels, making it ideal for a wide range of applications including high-frequency dc-dc converters, motor drivers, and class-D audio amplifiers, as confirmed by the company.

The new IC, named LT8418, bears a striking resemblance to the output stage utilized in the recently introduced GaN driving dc-dc controller ICs LTC7890 and LTC7891. Notably, both the high-side and low-side outputs of the LT8418 feature separate pull-up and pull-down connections on the IC package channels, enabling the use of additional resistors to fine-tune GaN transistor turn-on and turn-off times independently.

According to ADI, the split gate drivers incorporated in the LT8418 offer customers the flexibility to adjust the on-off behavior to address various control issues. The launch of LT8418 at APEC in California showcased the advanced capabilities of this new driver.

For both high-side and low-side drive, the output current sourcing is achieved through a 0.6Ω pull-up (4A peak), while sinking is facilitated by a 0.2Ω (8A peak) mechanism. Given the sensitivity of GaN gates to over-voltage, the high-side bootstrap in the LT8418 is not based on a conventional diode but rather a 'smart-switch' design.

During the dead time interval between top-gate turn-off to bottom-gate turn-on, or vice versa, the GaN power switch exhibits a reverse conduction voltage that can lead to potential damage if not managed properly. The smart bootstrap switch integrated into the LT8418 effectively controls bootstrap charging or blocking, safeguarding against over-charge of the bootstrap rail and permanent gate damage to the GaN power switch.