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
LTC3776
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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.

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Packaging

QFN-24, SSOP-24

LTC3776
LTC3776
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Order Info

Package Variations and Pricing

Part Number Package Pins Temp Price (1-99) Price (1k)* RoHS Data
LTC3776EGN SSOP 24 E $5.36 $3.75 View
LTC3776EGN#PBF SSOP 24 E $5.36 $3.75 View
LTC3776EGN#TR SSOP 24 E   $3.85 View
LTC3776EGN#TRPBF SSOP 24 E   $3.85 View
LTC3776EUF QFN 24 E $5.36 $3.75 View
LTC3776EUF#PBF QFN 24 E $5.36 $3.75 View
LTC3776EUF#TR QFN 24 E   $3.85 View
LTC3776EUF#TRPBF QFN 24 E   $3.85 View
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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.

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Applications

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

LTSpice / SwitcherCAD III is a powerful FREE circuit simulator and schematic capture program, providing macro models for 80% of Linear Technology's switching regulators, over 200 op amp models, as well as resistors, transistors and MOSFET models.

  • Step 1. If you do not already have a copy of LTSpice, click here to download and install LTSpice / SwitcherCAD III

  • Step 2. Once LTSpice is installed, click here for a ready to run  demonstration circuit of the LTC3776.

  • Step 3. If LTspice / SwitcherCAD III does not automatically open after clicking the above link, you can instead run the simulation by right clicking on the link and selecting “Save Target As”. After saving the file to your computer, start LTSpice and open the demonstartion circuit by selecting "Open" from the "File" menu.
For our complete list of hundreds of ready to run demo circuits, visit our LTspice / SwitcherCAD III Demo Circuits Collection

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