LTC3776 - Dual 2-Phase, No RSENSE Synchronous Controller for DDR/QDR Memory Termination

Features

  • No Current Sense Resistors Required
  • Out-of-Phase Controllers Reduce Required Input Capacitance
  • VOUT2 Tracks 1/2 VREF
  • Symmetrical Source/Sink Output Current Capability (VOUT2)
  • Spread Spectrum Operation (When Enabled)
  • Wide VIN Range: 2.75V to 9.8V
  • Constant Frequency Current Mode Operation
  • 0.6V ±1.5% Voltage Reference (VOUT1)
  • Low Dropout Operation: 100% Duty Cycle
  • True PLL for Frequency Locking or Adjustment
  • Internal Soft-Start Circuitry
  • Power Good Output Voltage Monitor
  • Output Overvoltage Protection
  • Micropower Shutdown: IQ = 9µA
  • Tiny Low Profile (4mm × 4mm) QFN and Narrow SSOP Packages

Typical Application

LTC3776 Typical Application
LTC3776 Typical Application

Description

The LTC3776 is a 2-phase dual output synchronous stepdown switching regulator controller for DDR/QDR memory termination applications. The second controller regulates its output voltage to 1/2 VREF while providing symmetrical source and sink output current capability.

The No RSENSE constant frequency current mode architecture eliminates the need for sense resistors and improves efficiency. Power loss and noise due to the ESR of the input capacitance are minimized by operating the two controllers out of phase.

The switching frequency can be programmed up to 750kHz, allowing the use of small surface mount inductors and capacitors. For noise sensitive applications, the LTC3776 switching frequency can be externally synchronized from 250kHz to 850kHz, or can be enabled for spread spectrum operation. Forced continuous operation reduces noise and RF interference. Soft-start for VOUT1 is provided internally and can be extended using an external capacitor.

The LTC3776 is available in the tiny thermally enhanced (4mm × 4mm) QFN package or 24-lead SSOP narrow package.

Protected by U.S. Patents including 5481178, 5929620, 6144194, 6580258, 6304066, 6611131, 6498466, patent pending on Spread Spectrum.

Packaging

CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
Drawing
RoHS
LTC3776EGN#PBF SSOP-24 GN E 05-08-1641 (GN24) Yes
LTC3776EGN#TRPBF SSOP-24 GN E 05-08-1641 (GN24) Yes
LTC3776EUF#PBF 4x4 QFN-24 UF E 05-08-1697 Yes
LTC3776EUF#TRPBF 4x4 QFN-24 UF E 05-08-1697 Yes


LTC3776 Package Drawing
LTC3776 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
LTC3776EGN#PBF SSOP-24 E $5.36 $3.75 Yes
LTC3776EGN#TRPBF SSOP-24 E $3.85 Yes
LTC3776EUF#PBF 4x4 QFN-24 E $5.36 $3.75 Yes
LTC3776EUF#TRPBF 4x4 QFN-24 E $3.85 Yes
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* 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 Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC829A LTC3776EUF | 2-Phase Dual Step-Down Converter For DDR/QDR Memory Termination, Vin = 2.75V-8V, Vout1 = 2.5V (5A@5Vin), Vout2=1.25V (+/-5A@5Vin) $150.00
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Click here to view our complete list of demo boards

Applications

  • DDR, DDR II and QDR Memory
  • SSTL, HSTL Termination Supplies
  • Servers, RAID Systems
  • Distributed DC Power Systems

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Design Tools

LTspice

LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

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LTC3776

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