Datasheet

LTC6102
LTC6102-1/LTC6102HV
13
6102fe
For more information www.linear.com/LTC6102
Dynamic Range vs Maximum
Power Dissipation in R
SENSE
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.
Figure 2. Kelvin Input Connection Preserves Accuracy
with Large Load Current and Large Output Current
LTC6102
R
OUT
V
OUT
6102 F02
R
IN
–
V
+
LOAD
R
SENSE
R
IN
+
–
+
V
+
–INF
V
–
OUT
V
REG
0.1µF
TIE AS CLOSE TO R
IN
AS POSSIBLE
–INS+IN
LOADV
+
V
–
OUTPUT
R
SENSE
*
R
OUT
LTC6102
R
IN
–
R
IN
+
C
REG
*VISHAY VCS1625 SERIES
WITH 4 PAD KELVIN CONNECTION
V
–
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 R
IN
.
This reduces the parasitic series resistance so that R
IN
may be as low as 1Ω, allowing high gain settings to be
used with very little gain error.
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
Selection of External Input Resistor, R
IN
The external input resistor, R
IN
, controls the transconduc-
tance of the current sense circuit, I
OUT
= V
SENSE
/R
IN
. For
example, if R
IN
= 100, then I
OUT
= V
SENSE
/100 or I
OUT
=
1mA for V
SENSE
= 100mV.
R
IN
should be chosen to provide the required resolution
while limiting the output current. At low supply voltage,
I
OUT
may be as much as 1mA. By setting R
IN
such that
MAXIMUM POWER DISSIPATION (W)
DYNAMIC RANGE (dB)
110
100
90
80
70
60
50
40
30
20
6102 AI01
0.001 0.01 0.1 1 10 100
MAX I
SENSE
= 1A
MAX I
SENSE
= 10A
MAX I
SENSE
= 100A
DYNAMIC RANGE RELATIVE
TO 10µV, MINIMUM V
SENSE
R
SENSE
= 10mΩR
SENSE
= 100mΩ
100dB: MAX
V
SENSE
= 1V
40dB: MAX
V
SENSE
= 1mV
R
SENSE
= 10µΩ
R
SENSE
= 100µΩ
R
SENSE
= 1Ω
R
SENSE
= 1mΩ