LTC6102HV Linear Technology, LTC6102HV Datasheet - Page 9

• Manufacturer Part Number: LTC6102HV
• Description: Zero Drift High Side Current Sense Amplifier
• Manufacturer: Linear Technology

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APPLICATIONS INFORMATION
excess of 10W at full scale! That much power loss can put
a signifi cant 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.
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 signifi cant 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 fl owing 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
110
100
90
80
70
60
50
40
30
20
0.001
DYNAMIC RANGE RELATIVE
TO 10μV, MINIMUM V
R
100dB: MAX
V
Dynamic Range vs Maximum
SENSE
Power Dissipation in R
SENSE
MAXIMUM POWER DISSIPATION (W)
R
MAX I
MAX I
MAX I
SENSE
0.01
= 1mΩ
= 1V
R
SENSE
SENSE
SENSE
SENSE
= 1Ω
R
SENSE
0.1
= 100mΩ
= 1A
= 10A
= 100A
= 100μΩ
SENSE
R
1
SENSE
R
SENSE
40dB: MAX
V
SENSE
= 10μΩ
SENSE
10
= 10mΩ
= 1mV
6102 F10
100
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 fl ows into –INF.
The –INS and –INF pins should be tied as close as possible
to R
R
be used with very little gain error.
Selection of External Input Resistor, R
The external input resistor, R
tance of the current sense circuit, I
example, if R
1mA for V
R
while limiting the output current. At low supply voltage,
IN
IN
IN
may be as low as 1Ω, allowing high gain settings to
should be chosen to provide the required resolution
Figure 2. Kelvin Input Connection Preserves Accuracy
with Large Load Current and Large Output Current
R
. This reduces the parasitic series resistance so that
SENSE
OUTPUT
LOAD
SENSE
V
+
R
OUT
IN
LTC6102/LTC6102HV
R
R
IN
IN
V
= 100, then I
–
+
= 100mV.
–
+IN
V
V
+
–
*VISHAY VCS1625 SERIES
WITH 4 PAD KELVIN CONNECTION
LTC6102
R
IN
TIE AS CLOSE TO R
+
–
LTC6102
R
SENSE
IN
OUT
–
, controls the transconduc-
*
= V
OUT
IN
R
AS POSSIBLE
SENSE
IN
V
–INS
V
OUT
LOAD
–INF
V
–
+
REG
C
+
REG
= V
IN
/100 or I
R
SENSE
OUT
6102 F02
V
OUT
0.1μF
/R
IN
OUT
. For
9
6102f
=