LTC6101/LTC6101HV
9
Rev I
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BLOCK DIAGRAM
OUT: Current Output. OUT will source a current that is
proportional to the sense voltage into an external resistor.
V
–
: Negative Supply (or Ground for Single-Supply
Operation).
–IN
: The internal sense amplifier will drive IN
–
to the same
potential as IN
+
. A resistor (R
IN
) tied from V
+
to IN
–
sets
the output current I
OUT
= V
SENSE
/R
IN
. V
SENSE
is the voltage
developed across the external R
SENSE
(Figure 1).
+IN: Must be tied to the system load end of the sense
resistor, either directly or through a resistor.
V
+
: Positive Supply Pin. Supply current is drawn through
this pin. The circuit may be configured so that the
LTC6101 supply current is or is not monitored along
with the system load current. To monitor only system
load current, connect V
+
to the more positive side of the
sense resistor. To monitor the total current, including the
LTC6101 current, connect V
+
to the more negative side
of the sense resistor.
The LTC6101 high side current sense amplifier (Figure 1)
provides accurate monitoring of current through a user-
selected sense resistor. The sense voltage is amplified 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 filter.
Theory of Operation
An internal sense amplifier loop forces IN
–
to have the
same potential as IN
+
. Connecting an external resis-
tor, R
IN
, between IN
–
and V
+
forces a potential across
R
IN
that is the same as the sense voltage across
R
SENSE
. A corresponding current, V
SENSE
/R
IN
, will
flow through R
IN
. The high impedance inputs of the
sense amplifier will not conduct this input current,
so it will flow through an internal MOSFET to the output pin.
The output current can be transformed into a voltage by
adding a resistor from OUT to V
–
. The output voltage is
then V
O
= V
–
+ I
OUT
• R
OUT
.
–
+
V
+
V
–
10V
OUT
6101 BD
LTC6101/LTC6101HV
V
BATTERY
I
OUT
V
SENSE
R
SENSE
I
LOAD
R
OUT
R
IN
–
+
L
O
A
D
V
OUT
= V
SENSE
x
R
OUT
R
IN
5k
5k
10V
–IN
+IN
Figure 1. LTC6101/LTC6101HV Block Diagram and Typical Connection
APPLICATIONS INFORMATION
PIN FUNCTIONS
