Remote-sense wires are a "necessary evil "in tightly-regulated, higher-current supplies (especially with longer supply leads), where they are needed to accurately sense the voltage at the load despite resistive (IR) loss in the supply leads. Unfortunately, while using sensing wires the solve the problem, it incurs extra wire runs, or PCB track real estate, as well as potential for problems if the sensing leads get disconnected or corrupted.
The LT4180 Virtual Remote Sense™ Controller from Linear Technology Corp. uses an unusual technique to eliminate the need for the pair of remote sensing leads. It provides a small, incremental change in measures the incremental voltage change which occurs with an incremental change in current in the wiring. The "ΔV/ΔI" interrogation is then used to infer the resistance and thus DC voltage drop in the supply wiring, so the proper supply/load compensation situation can be established. This allows a corrected, regulated voltage to be maintained at the load, despite the current and subsequent voltage drop in the supply leads.
LTC4180 Virtual Remote SenseǢ Controller eliminates the need for remote-sense leads at the load–often needed to eliminate any effect of IR drop in supply leads, and thus maintain proper regulation–by inferring lead impedance and thus voltage drop; it checks incremental current and voltage changes at the supply source to assess the situation at the load.
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The IC is compatible with both isolated and non-isolated supplies, and with any power-supply topology (there are a lot of them in use). Input voltage range is 3 to 50 V, and the LT4180 includes an internal reference with ±% accuracy over the operating temperature range. The device can drive an optocoupler, often used as the feedback isolation link in isolated supplies. It also includes standard controller functions such as undervoltage and overvoltage protection, as well as spread-spectrum modulation dither to reduce EMI by spreading the undesired energy spectrum while reducing peak value below regulatory or user-specified mandates.—Bill Schweber
Price, packaging, and availability: The LT4180 is available in an SSOP-24 package, in three temperature grades: extended (-40°C to +85°C; industrial (-40°C to +125°C), and military (-55 °C to +125 °C). Prices begin at $2.95 each in 1000-piece orders. It is available now.
For more information: Contact Linear Technology Corp, :http://www.linear.com