LTC3859AL

PRODUCTION

Triple Output, Buck/Buck/Boost Synchronous Controller with 28μA Burst Mode IQ

Data Sheet (Rev. D) Product Selection Table
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Overview

  • Low Operating IQ: 28μA (One Channel On)
  • Dual Buck Plus Single Boost Synchronous Controllers
  • Outputs Remain in Regulation Through Cold Crank Down to 2.5V
  • Wide Bias Input Voltage Range: 4.5V to 38V
  • Buck Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
  • Boost Output Voltage Up to 60V
  • RSENSE or DCR Current Sensing
  • 100% Duty Cycle for Boost Synchronous MOSFET Even in Burst Mode® Operation
  • Phase-Lockable Frequency (75kHz to 850kHz)
  • Programmable Fixed Frequency (50kHz to 900kHz)
  • Selectable Continuous, Pulse-Skipping or Low Ripple Burst Mode Operation at Light Loads
  • Very Low Buck Dropout Operation: 99% Duty Cycle
  • Adjustable Output Voltage Soft-Start or Tracking
  • Low Shutdown IQ: 10μA
  • Small 38-Lead 5mm × 7mm QFN and TSSOP Packages
  • AEC-Q100 Qualified for Automotive Applications

The LTC3859AL 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 LTC3859AL 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 LTC3859AL can operate from an input supply as low as 2.5V after start-up.

The 28μA 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 LTC3859AL features a precision 0.8V reference for the bucks, 1.2V reference for the boost and a power good output indicator. The PLLIN/MODE pin selects among Burst Mode operation, pulse-skipping mode, or continuous inductor current mode at light loads.

Compared to the LTC3859 and the LTC3859A, the LTC3859AL is fully pin-compatible, but with lower Burst Mode operation IQ (28µA with one channel on).

Quiescent Current (Burst Mode) Notes
LTC3859AL 28μA-One channel on, Buck
38μA-All three channels on		 Internal clamp on the INTVCC pin
LTC3859A 55μA-One channel on, Buck
80μA-All three channels on		 Internal clamp on the INTVCC pin. For new designs, we recommend LTC3859AL
LTC3859 55μA-One channel on, Buck
80μA-All three channels on		 For new designs, we recommend LTC3859AL

Applications

  • Automotive Always-On and Start-Stop Systems
  • Battery Operated Digital Devices
  • Distributed DC Power Systems
  • Multioutput Buck-Boost Applications
LTC3859AL
Triple Output, Buck/Buck/Boost Synchronous Controller with 28μA Burst Mode IQ
LTC3859AL Typical Application Efficiency and Power Loss vs Output Current Product Package 1 Product Package 2
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Circuit Monitors 1
LTC2960
RECOMMENDED FOR NEW DESIGNS 36V Nano-Current Two-Input Voltage Monitor
Protection Switches & Controllers 2
LTC4380
RECOMMENDED FOR NEW DESIGNS Low Quiescent Current Surge Stopper
LTC4359
RECOMMENDED FOR NEW DESIGNS Ideal Diode Controller with Reverse Input Protection
Switching Regulators & Controllers 1
LTC3899
RECOMMENDED FOR NEW DESIGNS 60V Low IQ, Triple Output, Buck/Buck/Boost Synchronous Controller with PassThru
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Tools & Simulations

LTspice

Models for the following parts are available in LTspice:

  • LTC3859
  • LTC3859AL

LTpowerCAD 2

Design tools for the following parts are available in LTpowerCAD:

  • LTC3859AL(BOOST)
  • LTC3859AL(BUCK)
LTspice

LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

LTpowerCAD

LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.

Evaluation Kits

eval board
schematic 1
DC2122A

LTC3859ALEUHF Demo Board | 4.5V ≤ VIN ≤ 36V; VOUT1: 5V @ 5A, VOUT2: 8.5V @ 3A, VOUT3: 10V @ 7A

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Product Details

Demonstration circuit 2122A is a triple output synchronous step-up/dual step-down supply featuring the LTC3859AL. This demonstration circuit is designed for two buck 5V/5A, 8.5V/3A outputs supplied by a boosted 10V/7A output. Benefiting from this feature, the buck outputs are able to maintain regulation over a wide input voltage range of 4.5V to 36V which is suitable for automotive or other battery fed applications. Also, the demonstration circuit uses a drop-in layout that the main buck circuit components fit in an area of ¾" by 1½", while the main boost circuit area is ¾" by 1¾". The package style for the LTC3859AL is a 38-pin exposed pad QFN package.
DC2122A
LTC3859ALEUHF Demo Board | 4.5V ≤ VIN ≤ 36V; VOUT1: 5V @ 5A, VOUT2: 8.5V @ 3A, VOUT3: 10V @ 7A
DC2122A - Schematic

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