LT8419

The EVAL-LT8419-BZ is a high-power, high-efficiency, six-phase bidirectional converter featuring the LTC7871 controller and LT8419 GaN drivers. Each phase uses an LT8419 half-bridge driver to drive EPC2361 GaN FETs, with the gate driver placed close to the FETs and driven by PWM signals from the LTC7871. The VHIGH and VLOW terminals serve as either inputs or outputs, depending on the direction of power flow. In buck mode, which is selected by SW1, the board converts 30V to 70V at VHIGH to a regulated 12V output at V_LOW. In boost mode, it converts 10V to 14V at V_LOW to a regulated 48V output at V_HIGH.

The maximum V_LOW current is 200A in either direction, limited by the selected inductors. Maximum output power is 2.4kW in buck mode across the specified input range, and 2.4kW in boost mode when V_LOW is 12V. External airflow is required for operation at maximum power.

Inductor current in each phase is sensed through a low 1mΩ resistor using a highly accurate AC/DC current-sensing architecture with low power dissipation. The LTC7871 constant-current loop provides DC current limiting for current flowing into or out of the VLOW terminal, depending on the state of the BUCK pin. This current limit is programmable through the SETCUR pin and can be monitored at the IMON pin.

The EVAL-LT8419-BZ includes a SPI-compatible serial port. With a DC2026C (Linduino^® One) demo board and QuikEval™ software on a host computer, the user can:

• Margin the regulated V_LOW or V_HIGH up or down.
• Margin the DC current limit up or down with the SETCUR pin.
• Adjust the frequency spread and modulation rate of the spread spectrum circuit when spread spectrum is enabled.
• Monitor the operational status and faults of the LTC7871.

The EVAL-LT8419-AZ evaluation board features the LT8419 driving two 100V enhanced gallium nitride (eGaN) devices in a half-bridge configuration. The circuit is optimized as a buck converter with 48V_HV to 24/12V_LV at a 1MHz switching frequency, but it can be used as a boost converter or other converter topologies consisting of a half-bridge.

An external PWM signal is required to drive the board. The LT8419 driver has powerful 0.2Ω pull-down and 0.6Ω pull-up drivers to control the gates of the two 100V GaN devices. It also integrates a smart integrated bootstrap switch to generate a balanced bootstrap voltage from V_CC with a minimum dropout voltage. The LT8419 provides split gate drivers to adjust the turn-on and turn-off slew rates of the GaN devices to suppress ringing and optimize EMI performance.