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LTC6102IDD

Precision Zero Drift Current Sense Amplifier

Linear Technology 

LTC6102

LTC6102-1/LTC6102HV

Applications Information

a significant load on the power supply and create thermal

design headaches. In addition, heating in the sense resistor

can reduce its accuracy and reliability.

In contrast, the large dynamic range of the LTC6102 allows

the use of a much smaller sense resistor. The LTC6102

allows the minimum sense voltage to be reduced to less

than 10µV. The peak sense voltage would then be 10mV,

dissipating only 1W at 100A in a 100µΩ sense resistor!

With a specialized sense resistor, the same system would

allow peak currents of more than 1000A without exceeding

the input range of the LTC6102 or damaging the shunt.

high-current paths, this error can be reduced by orders of

magnitude. A sense resistor with integrated Kelvin sense

terminals will give the best results. Figure 2 illustrates the

recommended method. Note that the LTC6102 has a Kelvin

input structure such that current flows into –INF. The –INS

and –INF pins should be tied as close as possible to RIN.

This reduces the parasitic series resistance so that RIN

may be as low as 1Ω, allowing high gain settings to be

used with very little gain error.

V+

TIE AS CLOSE TO RIN AS POSSIBLE

Dynamic Range vs Maximum

Power Dissipation in RSENSE

110

RSENSE = 100mΩ RSENSE = 10mΩ

100

RSENSE = 1Ω

90

80

100dB: MAX

VSENSE = 1V

70

60

40dB: MAX

VSENSE = 1mV

50

40

RSENSE = 10µΩ

RSENSE = 100µΩ

30

RSENSE = 1mΩ

20

0.001 0.01 0.1

1

10

100

MAXIMUM POWER DISSIPATION (W)

DYNAMIC RANGE RELATIVE

TO 10µV, MINIMUM VSENSE

MAX ISENSE = 1A

MAX ISENSE = 10A

MAX ISENSE = 100A

6102 AI01

Sense Resistor Connection

Kelvin connection of +IN and –INS to the sense resistor

should be used in all but the lowest power applications.

Solder connections and PC board interconnections that

carry high current can cause significant error in measure-

ment due to their relatively large resistances. One 10mm

× 10mm square trace of one-ounce copper is approxi-

mately 0.5mΩ. A 1mV error can be caused by as little

as 2A flowing through this small interconnect. This will

cause a 1% error in a 100mV signal. A 10A load current

in the same interconnect will cause a 5% error for the

same 100mV signal. An additional error is caused by the

change in copper resistance over temperature, which is in

excess of 0.4%/°C. By isolating the sense traces from the

RSENSE

RIN–

RIN+ +IN

LOAD

V–

+–

LTC6102

–INS

–INF

V+

VREG

0.1µF

OUT

VOUT

ROUT

RSENSE*

V+

LOAD

RIN–

RIN+

OUTPUT

ROUT

V–

LTC6102

CREG

V–

*VISHAY VCS1625 SERIES

WITH 4 PAD KELVIN CONNECTION

6102 F02

Figure 2. Kelvin Input Connection Preserves Accuracy

with Large Load Current and Large Output Current

Selection of External Input Resistor, RIN

The external input resistor, RIN, controls the transconduc-

tance of the current sense circuit, IOUT = VSENSE/RIN. For

example, if RIN = 100, then IOUT = VSENSE/100 or IOUT =

1mA for VSENSE = 100mV.

RIN should be chosen to provide the required resolution

while limiting the output current. At low supply voltage,

IOUT may be as much as 1mA. By setting RIN such that

For more information www.linear.com/LTC6102

6102fe

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