LTC6102CDD LINER [Linear Technology], LTC6102CDD Datasheet - Page 8

• Manufacturer Part Number: LTC6102CDD
• Description: Precision Zero Drift Current Sense Amplifi er
• Manufacturer: LINER [Linear Technology]

BLOCK DIAGRAM
LTC6102/LTC6102HV
APPLICATIONS INFORMATION
The LTC6102 high side current sense amplifi er (Figure 1)
provides accurate monitoring of current through a user-
selected sense resistor. The sense voltage is amplifi ed by
a user-selected gain and level shifted from the positive
power supply to a ground-referred output. The output
signal is analog and may be used as is or processed with
an output fi lter.
Theory of Operation
An internal sense amplifi er loop forces –INS to have the
same potential as +IN. Connecting an external resistor,
R
that is the same as the sense voltage across R
corresponding current, V
The high impedance inputs of the sense amplifi er will not
conduct this input current, so it will fl ow through the –INF
pin and an internal MOSFET to the output pin.
The output current can be transformed into a voltage by
adding a resistor from OUT to V
then V
Useful Gain Confi gurations
8
IN
, between –INS and V
GAIN
1000
4990
200
500
O
= V
–
+ I
49.9Ω
20Ω
10Ω
R
1Ω
OUT
IN
I
LOAD
• R
O
D
L
A
OUT
4.99k
SENSE
R
10k
10k
10k
+
OUT
.
–
forces a potential across R
R
V
SENSE
SENSE
Figure 1. LTC6102/LTC6102HV Block Diagram and Typical Connection
/R
IN
–
+
. The output voltage is
, will fl ow through R
R
IN
V
SENSE
+IN
–INF
–INS
LTC6102/LTC6102HV
25mV
10mV
AT V
5mV
1mV
10V
OUT
5k
5k
SENSE
= 5V
5V
. A
10V
IN
IN
.
V
–
–
+
V
BATTERY
Selection of External Current Sense Resistor
The external sense resistor, R
on the function of a current sensing system and must be
chosen with care.
First, the power dissipation in the resistor should be
considered. The system load current will cause both heat
dissipation and voltage loss in R
resistor should be as small as possible while still providing
the input dynamic range required by the measurement.
Note that input dynamic range is the difference between
the maximum input signal and the minimum accurately
reproduced signal, and is limited primarily by input DC
offset of the internal amplifi er of the LTC6102. In addition,
R
the maximum sense voltage specifi ed by the LTC6102 or
the sense resistor, even under peak load conditions. As
an example, an application may require that the maximum
sense voltage be 100mV. If this application is expected
to draw 20A at peak load, R
than 5mΩ.
Once the maximum R
minimum sense resistor value will be set by the resolu-
tion or dynamic range required. The minimum signal
that can be accurately represented by this sense amp is
limited by the input offset. As an example, the LTC6102
has a typical input offset of 3μV. If the minimum current
is 1mA, a sense resistor of 3mΩ will set V
SENSE
V
V
–
+
10V
must be small enough that V
0.1μF
5V
V
REG
OUT
6102 BD
I
OUT
R
OUT
SENSE
V
OUT
= V
SENSE
SENSE
SENSE
SENSE
value is determined, the
x
, has a signifi cant effect
R
SENSE
R
OUT
. As a result, the sense
IN
should be no more
does not exceed
SENSE
to 3μV.
6102fb