LTC7821

Hybrid Step-Down Synchronous Controller

Data Sheet

Rev. A

Recommended for New Designs

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Alternative Parts

LTC7820

Fixed Ratio High Power Inductorless (Charge Pump) DC/DC Controller

New Content (1)

Evaluation Kit Manuals

DC2787A - Demo Manual

Overview

Features and Benefits
Product Details

Features and Benefits

Wide V_IN Range: 10V to 72V (80V ABS Max)
Soft Switching for Low Noise Operation
Phase-Lockable Fixed Frequency 200kHz to 1.5MHz
±1% Output Voltage Accuracy
R_SENSE or DCR Current Sensing
Programmable CCM, DCM, or Burst Mode^® Operation
CLK_OUT Pin for Multiphase Operation
Short Circuit Protected
EXTV_CC Input for Improved Efficiency
Monotonic Output Voltage Start-Up
Optional External Reference
32-Pin (5mm × 5mm) QFN

Product Details

The LTC7821 uses a proprietary architecture that merges a soft switching charge pump topology with a synchronous step-down converter to provide superior efficiency and EMI performance compared to traditional switching architectures.

In a typical 48V to 12V application, efficiency of greater than 97% is attainable with the LTC7821 switching at 500kHz. The same efficiency can only be achieved with a traditional controller switching at one-third the frequency. Higher switching frequencies allow the use of smaller inductances that yield faster transient response and smaller solution size.

The LTC7821 can be easily paralleled to provide higher output currents with its accurate current sharing capability and frequency synchronization function.

Applications

Intermediate Bus Converters
High Current Distributed Power Systems
Telecom, Datacom, and Storage Systems

Product Categories

Power Management

Markets & Technology

Data Center

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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 (2)

DC2787A

LTC7821 Demo Board | 40V ≥ V_IN ≥ 60V, V_OUT = 12V @ 100A

DC2513A

LTC7821EUH Demo Board | 36V ≤ V_IN ≤ 72V; V_OUT = 12V at 20A, 97.5% Efficiency/500kHz

DC2787A

View Detailed Evaluation Kit Information

Demonstration circuit 2787A is a high efficiency, 4 phase, hybrid converter. It can deliver 12V/100A with the input voltage from 40V to 60V. The demo board features the LTC7821, which uses an architecture that merges a soft-switching switched-capacitor topology with a traditional step-down converter to provide superior efficiency compared to the traditional switching architectures. It offers a high efficiency/high density and cost effective solution for nonisolated intermediate bus applications in power distribution, datacom and telecom as well as emerging 48V automotive systems.

External MOSFETs switch at a 400kHz fixed frequency for this demo board and can be programmed from 200kHz to 1.5MHz. The LTC7821’s powerful 1Ω N-channel MOSFET gate drivers maximize efficiency and can drive multiple MOSFETs in parallel for higher power applications. Due to its current mode control architecture, multiple LTC7821 devices can be operated in a parallel, multiphase configuration with excellent current sharing and low output voltage ripple to enable much higher power applications. Other benefits include low EMI emissions due to a soft-switched front end and reduced MOSFET stress.

The LTC7821 design eliminates the inrush current typically associated with switched capacitor circuits by prebalancing the capacitors on start-up. The LTC7821 also monitors system voltage, current and temperature for faults, and uses a sense resistor for overcurrent protection. It stops switching and pulls the FAULT pin low when a fault condition occurs. An onboard timer can be set for appropriate restart/retry times. Additional features include ±1% output voltage accuracy over temperature, a clock output for multiphase operation, a power good output signal, short-circuit protection, monotonic output voltage start-up, optional external reference, undervoltage lockout and internal charge balance circuitry. The LTC7821 data sheet must be used in conjunction with this demo board manual.

Resources

DC2513A

View Detailed Evaluation Kit Information

Demonstration circuit 2513A is a high efficiency, high power density hybrid converter. It can deliver 12V/20A with an input voltage from 36V to 72V. This demo board features the LTC7821, which uses an architecture that merges soft-switching switched-capacitor topology with a traditional step-down converter to provide superior efficiency compared to the traditional switching architectures. It offers a high efficiency/high density and cost effective solution for non isolated intermediate bus applications in power distribution, datacom and telecom as well as emerging 48V automotive systems.

Resources

Documentation

Data Sheets (1)

PDF

1.53 M

LTC7821: Hybrid Step-Down Synchronous Controller Data Sheet (Rev. A)

Evaluation Kit Manuals (2)

PDF

1.8 M

DC2787A - Demo Manual

PDF

686.00K

DC2513A - Demo Board Manual

Design Notes (1)

Hybrid Converter Simplifies 48 V/54 V Step-Down Conversion in Data Centers and Telecom Systems

Tools & Simulations

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.

LTspice downloads and documentation

Models for the following parts are available in LTspice:

LTC7821

Product Recommendations

LTC7821 Companion Parts

Recommended Related Parts

LTC4260, LTC2975.

Reference Materials

Product Selector Card (1)

80V to 150V Non-Isolated DC/DC

White Papers (1)

72V Hybrid DC/DC Reduces Intermediate Bus Converter Size by Up to 50%

Videos (2)

LTC7821: Hybrid Synchronous Step-Down Controller

High Power, High Density Switched Capacitor & Hybrid Converter

Technical Articles (1)

Cascaded and Hybrid Concepts for Voltage Conversion

Press Releases (1)

ADI 72V Hybrid Step-Down DC/DC Controller Reduces Solution Size by 50%...

Design Resources

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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.

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