Features and Benefits
- Dual Buck Plus Single Boost Synchronous Controllers
- Low Operating IQ: 14μA (14V to 3.3V, Channel 1 On)
- Outputs Remain in Regulation Through Cold Crank Down to 1V Input Supply Voltage
- Wide Bias Input Voltage Range: 4.5V to 40V
- Buck and Boost Output Voltages up to 40V
- Spread Spectrum Operation
- RSENSE or DCR Current Sensing
- Programmable Fixed Frequency (100kHz to 3MHz)
- PassThru™/100% Duty Cycle Capable for Synchronous Boost MOSFET
- Phase-Lockable Frequency (100kHz to 3MHz)
- Selectable Continuous, Pulse-Skipping, or Low Ripple Burst Mode Operation at Light Loads
- Boost Channel Current Monitor Output
- Low Shutdown IQ: 1.5μA
- Small 40-Lead 6mm × 6mm QFN Package
- AEC-Q100 Qualified for Automotive Applications
The LTC7818 is a high performance triple output (buck/buck/boost) synchronous DC/DC switching regulator controller that drives all N-channel power MOSFET stages. Its constant-frequency current mode architecture allows a phase-lockable switching frequency of up to 3MHz. The LTC7818 operates from a wide 4.5V to 40V input supply range. When biased from the output of the boost converter or another auxiliary supply, the LTC7818 can operate from an input supply as low as 1V after start-up.
The LTC7818 synchronous boost PassThru capability minimizes losses in automotive start-stop applications. The very low no-load quiescent current extends operating run time 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 LTC7818 features a precision 0.8V reference for the bucks, 1.2V reference for the boost and a power good output indicator.
The LTC7818 additionally features spread spectrum operation which significantly reduces the peak radiated and conducted noise on both the input and output supplies, making it easier to comply with electromagnetic interference (EMI) standards.
- Automotive and Transportation
Product Lifecycle Recommended for New Designs
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Evaluation Kits (1)
Demonstration circuit DC2855A is a triple output synchronous step-up/dual step-down supply featuring the LTC 7818. The demonstration circuit is designed for two buck outputs 5V/10A, 3.3V/10A supplied by a boosted 10V 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 whereas 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 LTC7818 is a 40-pin exposed pad QFN.
The main features of the board include rail tracking (Buck channels only), an internal 5V linear regulator for bias, separated RUN pins for each output, a PGOOD signal (CH1 only), an overvoltage indicator for CH3 and a Mode selector that allow the converter to run in CCM, Pulseskipping or Burst Mode operation. Spread Spectrum Mode is availiable for EMI improvement. Synchronization to an external clock is also possible. The LTC7818 datasheet gives a complete description of these parts, operation and application information. The datasheet must be read in conjunction with this quick start guide for demo circuit 2855A.
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.
To open the project file for this circuit:
Step 1: Download and install LTpowerCAD on your computer.
Step 2: Click on the link(s) in the section below to download part-specific project files.
Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.
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.