1
dc2261af
DEMO MANUAL DC2261A
Description
High Side Current Sense
with Comparators and a
400mV Reference
Demonstration circuit 2193A features the
, a
high side current sense amplifier with comparators and
a 400mV reference.
The demo board circuit amplifies the voltage across an
onboard current sense resistor, to provide a precision
unipolar voltage output that is proportional to the sensed
current. The board has two onboard comparators with latch-
ing outputs and an integrated 400mV reference that sets
the threshold for the comparators. There are two versions
of the board, A and B. The version determines the available
comparator inputs. The DC2261A-A (LT6119-1) has an
inverting and a noninverting comparator input available
while the DC2261A-B (LT6119-2) has two inverting inputs
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
performance summary
available. The demonstration board includes circuitry to
guarantee that the comparator resets on power up. The
current sense gain and current fault limits are set by on
board resistors. The default gain is set at 10V/A and the
comparators are set to trip at current thresholds of 50mA
and 300mA.
The key performance specifications are listed in the table
below.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2261A
Specifications are at T
A
= 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input Supply Range
2.7
60
V
V
OUTA
Measured Output Signal
I
LOAD
= 100mA
1
V
I
LOAD
Output Load Current Range
Thermal Limit of R
SENSE
3
A
I
Q
IN Quiescent Current
V
IN
= 12V
600
µA
I
THR1
Comparator1 Threshold
V
OUTA
= 3V
300
mA
I
THR2
Comparator2 Threshold
V
OUTA
= 0.5V
50
mA
operating principles
The LT6119 operates by amplifying the voltage drop across
a sense resistor that is in series with the load. The sense
inputs of the amplifier differentially measure the sense
resistor voltage drop to control an internal variable current
source that allows translation of the input voltage level to
a level referenced to the GND. The circuit gain is set by
the ratio of the output resistor to the input resistor. The
comparator thresholds are set by the internal reference
and the current trip points are set by dividing the output
resistance into a network of three resistors. The RC filter
connected to the latch enable (LE) pin guarantee that the
latch enable pin is held low long enough on start-up to
reset the comparator output on power on.
The DC2261A is shipped with a 100mΩ sense resistor.
The amplifier gain is configured for 100V/V, providing an
overall circuit gain of 10V/A. The current fault thresholds
are set at 50mA and 300mA.
