GENERAL DESCRIPTION
The LTC7891 is a high performance, step-down, dc-to-dc switching
regulator controller that drives all N-channel synchronous gallium
nitride (GaN) field effect transistor (FET) power stages from input
voltages up to 100 V. The LTC7891 solves many of the challenges
traditionally faced when using GaN FETs. The LTC7891 simplifies
the application design while requiring no protection diodes and no
other additional external components compared to a silicon metaloxide
semiconductor field effect transistor (MOSFET) solution.
The internal smart bootstrap switch prevents overcharging of the
BOOST pin to SW pin high-side driver supplies during dead times,
protecting the gate of the top GaN FET. The LTC7891 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 LTC7891 can be precisely adjusted
from 4 V to 5.5 V to optimize performance, and to allow the use of
different GaN FETs, or even logic level MOSFETs.
Note that throughout this data sheet, multifunction pins, such as
PLLIN/SPREAD, are referred to either by the entire pin name or
by a single function of the pin, for example, PLLIN, when only that
function is relevant.

FEATURES
► GaN drive technology fully optimized for GaN FETs
► Wide VIN 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 highside
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 operating IQ: 5 μA (48 VIN to 5 VOUT)
► Programmable frequency (100 kHz to 3 MHz)
► Phase lockable frequency (100 kHz to 3 MHz)
► Spread spectrum frequency modulation
► 28-lead (4 mm × 5 mm) side wettable QFN package

APPLICATIONS
► Industrial power systems
► Military avionics and medical systems
► Telecommunications power systems