LT4180IGN-PBF datasheet(7/16 Pages) LINER

7 / 16 page

LT4180

4180fp

OPERATION

Voltage drops in wiring can produce considerable load

regulation errors in electrical systems (Figure 1). As

load current, IL, increases the voltage drop in the wiring

(IL • RW) increases and the voltage delivered to the system

(VL)drops.Thetraditionalapproachtosolvingthisproblem,

remote sensing, regulates the voltage at the load, increas-

ing the power supply voltage (VOUT) to compensate for

voltage drops in the wiring. While remote sensing works

well, it does require an additional pair of wires to measure

at the load, which may not always be practical.

The LT4180 eliminates the need for a pair of remote sense

wires by creating a Virtual Remote Sense. Virtual remote

sensing is achieved by measuring the incremental change

in voltage that occurs with an incremental change in current

in the wiring (Figure 2). This measurement can then be

used to infer the total DC voltage drop in the wiring, which

can then be compensated for. The Virtual Remote Sense

takes over control of the power supply via the feedback

pin (VFB) of the power supply maintaining tight regulation

of load voltage, VL.

Figure 3 shows the timing diagram for virtual remote sens-

ing (VRS). A new cycle begins when the power supply and

VRS close the loop around VOUT (regulate VOUT = H). Both

VOUT and IOUT slew and settle to a new value, and these

values are stored in the Virtual Remote Sense (track VOUT

high = L and track IOUT = L). The VOUT feedback loop is

opened and a new feedback loop is set up commanding the

power supply to deliver 90% of the previously measured

current (0.9IOUT). VOUT drops to a new value as the power

supply reaches a new steady state, and this information

is also stored in the Virtual Remote Sense. At this point,

the change in output voltage (ΔVOUT) for a –10% change

in output current has been measured and is stored in the

Virtual Remote Sense. This voltage is used during the

next VRS cycle to compensate for voltage drops due to

wiring resistance.

Figure 1. Traditional Remote Sensing

Figure 2. Virtual Remote Sensing

Figure 3. Simpliﬁed Timing Diagram, Virtual Remote Sense

4180 F02

POWER WIRING

VIRTUAL REMOTE

SENSE

POWER SUPPLY

–

VOUT

VFB

SYSTEM

–

4180 F01

POWER WIRING

REMOTE SENSE WIRING

POWER SUPPLY

–

VOUT

SYSTEM

–

VOUT

TRACK ΔVOUT

REGULATE VOUT

TRACK VOUT HIGH

TRACK IOUT

REGULATE IOUT LOW

TRACK VOUT LOW

4180 F03

LT4180IGN-PBF Datasheet(PDF) 7 Page - Linear Technology

LT4180IGN-PBF Datasheet(HTML) 7 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Datasheet Download

Link URL