Linear Technology Corporation LT4180 Backgrounder Tony Armstrong Director of Product Marketing.

Linear Technology Corporation

LT4180 Backgrounder

Tony ArmstrongDirector of Product Marketing

© 2006 Linear Technology

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LT4180 Virtual Remote Sense Controller

Background• Limitations of Remote Voltage Sensing w/ Wires• Advantages of Virtual Remote Sensing w/o Wires

LT4180• Definition• Features & Benefits• How Does it Work• How Well Does it Work• Application Circuits• Target Markets• Target Applications


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Remote Sense Background

• Why Remote Sense?• Voltage drop (IR Losses) in cables and wiring• IR losses can cause the regulation at the load to exceed its

limit• Remote sense with 2 wires works but has limitations

• Remote Sense Wire Limitations• Extra wires can be impractical • Less reliable• Higher cost• Not available in 2-wire cables


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LT4180: Virtual Remote Sense – What is it?


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LT4180: VRS Block Diagram and Waveform

NOTE: Voltage at the load is 5V


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LT4180 Virtual Remote Sense Features

• Tight Load Regulation with Highly Resistive Cables without Requiring Remote Sense Wires

• Compatible with all Conversion Topology’s including Isolated and Non-Isolated Power Supplies

• VIN Range: 3V to 50V• Wide VOUT Range: 1.21V to 50V• 5mA Sink Current Capability to Drive Opto-Coupler• Accurate ±1% Internal Reference Voltage• Soft-Correct Reduces Turn-On Transients• Undervoltage and Overvoltage Protection• Programmable or Synchronizable Dither Frequency• Optional Spread Spectrum Dither Frequency


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LT4180: How Does it Work?

• LT4180 forces a current delta of ±5% of the output current• Square wave current at a programmable dither frequency• A decoupling capacitor filters out dither current at the load

and is sized for low impedance (AC short) at the programmed dither frequency

• This results in a voltage equal to 1/10 the drop in the cable• The LT4180 adjusts the regulation voltage locally at the

regulator output to compensate for the cable drop. This assures tight regulation at the other end of the cable, where the load is.


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LT4180 – How Well Does it Work?


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LT4180: Typical Buck Application Schematic


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LT4180: Typical Isolated Application Schematic


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LT4180: Typical Boost (5V12V) Applications Schematic


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LT4180: Package


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LT4180 Typical Applications

• CAT5 & CAT6 Cable Systems• Wall Adaptors• Notebook Computer Power• Remote Surveillance Equipment• Halogen Lighting• Well-Logging• Remote Instrumentation• Battery Charging• PDA’s


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LT4180: Conclusion

• LT4180 is a revolutionary new way to compensate for wiring and cable voltage drops

• Limitless applications• Works with any conversion topology• Numerous features & benefits

Linear Technology Corporation LT4180 Backgrounder Tony Armstrong Director of Product Marketing.

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