The LTC®3859 is a high performance triple output (buck/
buck/boost) synchronous DC/DC switching regulator
controller that drives all N-channel power MOSFET stages.
Constant frequency current mode architecture allows a
phase-lockable switching frequency of up to 850kHz. The
LTC3859 operates from a wide 4.5V to 38V input supply
range. When biased from the output of the boost converter
or another auxiliary supply, the LTC3859 can operate from
an input supply as low as 2.5V after start-up.
The 55μA no-load quiescent current extends operating
runtime in battery powered systems. OPTI-LOOP compensation allows the transient response to be optimized
over a wide range of output capacitance and ESR values.
The LTC3859 features a precision 0.8V reference for the
bucks, 1.2V reference for the boost and a power good
output indicator.
Independent TRACK/SS pins for each controller ramp the
output voltages during start-up. Current foldback limits
MOSFET heat dissipation during short-circuit conditions.
The PLLIN/MODE pin selects among Burst Mode operation, pulse-skipping mode, or continuous inductor current
mode at light loads
n Dual Buck Plus Single Boost Synchronous Controllers
n Outputs Remain in Regulation Through Cold Crank
Down to 2.5V
n Low Operating IQ: 55μA (One Channel On)
n Wide Bias Input Voltage Range: 4.5V to 38V
n Buck Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
n Boost Output Voltage Up to 60V
n RSENSE or DCR Current Sensing
n 100% Duty Cycle for Boost Synchronous MOSFET
n Phase-Lockable Frequency (75kHz to 850kHz)
n Programmable Fixed Frequency (50kHz to 900kHz)
n Selectable Continuous, Pulse-Skipping or Low Ripple
Burst Mode® Operation at Light Loads
n Very Low Buck Dropout Operation: 99% Duty Cycle
n Adjustable Output Voltage Soft-Start or Tracking
n Low Shutdown IQ: 14μA
n Small 38-Pin 5mm × 7mm QFN and TSSOP Packages
n Automotive Always-On and Start-Stop Systems
n Battery Operated Digital Devices
n Distributed DC Power Systems
