Datasheet

LT6109-1/LT6109-2
10
610912fa
BLOCK DIAGRAMS
Figure 2. LT6109-2 Block Diagram (Comparators with the Same Polarity)
APPLICATIONS INFORMATION
The LT6109 high side current sense amplifier provides
accurate monitoring of currents through an external sense
resistor. The input sense voltage is level-shifted from the
sensed power supply to a ground referenced output and
is amplified by a user-selected gain to the output. The
output voltage is directly proportional to the current flow-
ing through the sense resistor.
The LT6109 comparators have a threshold set with a built-in
400mV precision reference and have 10mV of hysteresis.
The open-drain outputs can be easily used to level shift
to digital supplies.
Amplifier Theory of Operation
An internal sense amplifier loop forces SENSEHI to have
the same potential as SENSELO as shown in Figure 3.
Connecting an external resistor, R
IN
, between SENSEHI
and V
SUPPLY
forces a potential, V
SENSE
, across R
IN
. A
corresponding current, I
OUTA
, equal to V
SENSE
/R
IN
, will
flow through R
IN
. The high impedance inputs of the sense
amplifier do not load this current, so it will flow through
an internal MOSFET to the output pin, OUTA.
100Ω
OUTA
–
+
–
+
9
10
1
8
INC2
7
INC1
610912 F02
6
V
+
V
–
V
–
V
–
V
–
V
+
3k
V
+
3k
SENSEHI
LT6109-2
SENSELO
200nA
RESET
OVERCURRENT FLAG
OVERCURRENT FLAG
2
EN/RST
3
OUTC2
4
OUTC1
34V 6V
ENABLE AND
RESET TIMING
–
+
V
–
V
+
5
400mV
REFERENCE