DC2995A

The LTC7890/LTC7891 devices drive all N-channel synchronous gallium nitride (GaN) field effect transistor (FET) power stages from input voltages up to 100 V. The LTC7890 solves many of the challenges traditionally faced when using GaN FETs. The LTC7890 simplifies the application design while requiring no protection diodes and no other additional external components compared to a silicon metal-oxide semiconductor field effect transistor (MOSFET) solution.

The internal smart bootstrap switches prevent overcharging of the BOOSTx pin to the SWx pin high-side driver supplies during dead times, protecting the gate of the top GaN FET. The LTC7890 internally optimizes the gate driver timing on both switching edges to achieve smart near-zero dead times, significantly improving efficiency and allowing for high-frequency operation, even at high input voltages. Alternatively, the user can adjust the dead times with external resistors for margin or to tailor the application.

The gate drive voltage of the LTC7890 can be precisely adjusted from 4V to 5.5V to optimize performance and to allow the use of different GaN FETs or even logic-level MOSFETs.

Key Features and Benefits

• •  GaN drive technology fully optimized for GaN FETs
• •  Wide V_IN range: 4 V to 100 V
• •  Wide output voltage range: 0.8 V ≤ VOUT ≤ 60 V
• •  No catch, clamp, or bootstrap diodes needed
• •  Internal smart bootstrap switches prevent overcharging of high-side driver supplies
• •  Internally optimized, smart near zero dead times or resistor adjustable dead times
• •  Split output gate drivers for adjustable turn on and turn off driver strengths
• •  Accurate adjustable driver voltage and UVLO
• •  Low I_Q: 5 μA (48 V_IN to 5 V_OUT, Ch 1 On)
• •  Programmable frequency (100 kHz to 3 MHz)
• •  Synchronizable frequency (100 kHz to 3 MHz)
• •  Spread spectrum frequency modulation
• •  40-lead (6 mm × 6 mm), side wettable, QFN package

Applications

• •  Industrial power systems
• •  Military avionics and medical systems
• •  Telecommunications power systems

Evaluation Board

The LTC7890/LTC7891 can be evaluated with the DC2938A.

Block Diagrams and Tables