Linear Design Features - LTJournal-V20N2-00-Cover-LT4180-Tom_Hack User Manual
Summary
This guide details Virtual Remote Sensing (VRS), an advanced control method designed to solve critical power loss issues in sensitive electrical systems. VRS addresses voltage fluctuations—or IR drop—that occur over long wiring runs, which traditionally requires complex sensing lines or bulky compensation circuits. This technique provides excellent load-end regulation while remaining simple to implement and avoiding the limitations of conventional remote sensing techniques. It is ideal for engineers designing data center power supplies, FPGA servers, or any application requiring precise voltage maintenance at the load point.
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July 2010 Volume 20 Number 2
Virtual Remote Sensing
analog multiplier monitors instantaneous power and simplifies design of Improves Load Regulation by power control loops 10
Compensating for Wiring Drops
regulator with accurate input current limit safely extracts maximum power Without Remote Sense Lines from USB 22
Tom Hack and Robert Dobkin
clean, efficient, high
current point-of-load Accurately regulating a voltage at a load can be difficult when there
power for FPGA and server are significant voltage drops between the power supply and the backplanes 28
load. Even if a regulator produces a perfectly regulated voltage at its
own output, variations in load current affect the IR drop along the wiring, resulting in significant voltage fluctuations at the load (see Figure 1). The conventional solution to improving regulation at the load involves adding extra wires for remote sensing (Figure 2a), but adding extra wires is not always desirable, or even pos- sible. A new control method, Virtual Remote Sensing™ (VRS™), easily replaces and avoids the pitfalls of conventional solu-
CONNECTOR WIRING DROPS CONNECTOR tions and in some instances solves the previously insoluble. POWER DROPS DROPS
SUPPLY
LOAD-END REGULATION BEFORE VRS CONNECTOR WIRING DROPS CONNECTOR Virtual Remote Sensing solves the problem of maintain-
DROPS DROPS
ing load regulation at the end of long wiring runs. VRS is easier to implement and generally performs better than conventional
Figure 1. The simplest model for load regulation over remote sensing techniques such as direct remote voltage sens- resistive interconnections.
ing, voltage-drop compensation, and load-end regulation.
The first conventional technique, direct remote sensing (Figure 2a), produces excellent load-end regulation, but it requires two pairs of wires: one pair to provide the load current and a second pair to measure the voltage at the load for proper regulation. Traditionally, remote sensing requires foresight—it must be
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Page Summary Contents For Linear Design Features - LTJournal-V20N2-00-Cover-LT4180-Tom_Hack User Manual
Manual Details
| Brand | Linear |
|---|---|
| Pages | 8 |
| File Size | 1.75 MB |
| Published | June 18, 2026 |
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Frequently Asked Questions
What problem does Virtual Remote Sensing (VRS) solve?
It solves the issue of maintaining load regulation at the end of long wiring runs, where voltage drops occur due to resistance.
How is VRS better than conventional remote sensing methods?
VRS avoids the need for extra sense wires and improves performance compared to traditional direct remote sensing or simple voltage drop compensation techniques.
Does VRS require additional components?
It works with virtually any power supply or regulator (switching, isolated, non-isolated, synchronized, or unsynchronized).
What is a key feature of the LT4180 VRS circuit?
The system includes features like undervoltage and overvoltage lockout, and optoisolator drivers.