Features and Benefits
- 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
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|
- Automotive Always-On and Start-Stop Systems
- Battery Operated Digital Devices
- Distributed DC Power Systems
- Multioutput Buck-Boost Applications
Markets & Technology
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
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.
Tools & Simulations
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.
Models for the following parts are available in LTspice:
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.
Design tools for the following parts are available in LTpowerCAD:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.