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DEMO MANUAL DC2193A
Description
LT6118
High Side Current Sense Amplifier with Reference
and Comparator with POR Capability
Demonstration circuit 2193A features the LT
®
6118, a
high side current sense amplifier with a comparator and
a 400mV reference.
The demo board circuit amplifies the voltage across an on-
board current sense resistor, to provide a precision unipolar
voltage output that is proportional to the sensed current.
The board has one on-board latching comparator and an
integrated 400mV reference that sets the threshold for the
comparator. The demonstration board includes circuitry
to guarantee that the comparator resets on power up. The
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
current sense gain and current fault limits are set by on
board resistors. The gain is 2.5V/A and the comparator
is set to trip at current threshold of 500mA.
The key performance specifications are listed in the table
below.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2193A
Specifications are at TA = 25°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Input Supply Range 2.7 60 V
VIOUT Measured Output Signal ILOAD = 100mA 250 mV
IIOUT Measured Output Signal(Current Mode) VIOUT = 250mV 100 µA
IOUT Output Load Current Range Thermal Limit of RSENSE 4 A
IQVIN Quiescent Current VIN = 12V 800 µA
VTHR Comparator Threshold VIOUT = 1.25V 500 mA
The LT6118 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 LT6118 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 guaran-
tee that the LE pin is held low long enough on startup to
reset the comparator output on power on. The DC2193 is
shipped with a 100mΩ sense resistor. The amplifier gain
is 25V/V, providing an overall circuit gain of 2.5V/A. The
overcurrent fault threshold is set to 500mA.
operating principles
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DEMO MANUAL DC2193A
Block Diagram
100Ω
OUTA
–
+
–
+
7
8
16
INC 5
6118 F01
V+
V–
V–
V–
V–
V+
3k
V+
3k
SENSEHI
SENSELO
100nA
OVERCURRENT FLAG
2LE
3OUTC
34V 6V
V–
4
400mV
REFERENCE
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DEMO MANUAL DC2193A
Quick start proceDure
The DC2193A provides a simple way to evaluate the per-
formance of the LT6118. Refer to Figure 1 for proper mea-
surement equipment setup and follow these procedures:
1. With the power off, connect the power supply positive
to IN and the common to GND. With default board
settings the supply can range from 2.7V to 60V. If the
supply does not have an accurate current readout, a
DMM may be connected in series with the supply as
shown in Figure 1.
2. Connect a DMM or oscilloscope to the IOUT with the
common connection connected to ground.
3. Connect a load to the demo boards OUT terminal (posi-
tive) and ground. The load may be a power resistor,
active load instrument or a circuit of interest.
4. Turn on the power supply. The comparator will reset
during power on and will start in the correct state based
on the load current. With the load shown in Figure 1
the comparator output should be at 20V
5. Measure the output voltage and confirm that it corre-
sponds to the load current. VIOUT = 2.5 • ILOAD(A) with
the provided resistors.
6. If able, sweep load current from 0mA to 500mA to verify
the operation of the comparator. OUTC will latch low
when ILOAD exceeds 500mA.
0.10A
20.0
0.25V
LOAD
RESET
Figure 1
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DEMO MANUAL DC2193A
operation
Current Sense Gain
The gain of the LT6118 current sense amplifier is set by
the ratio of ROUT and RIN resistors. In the demo circuit this
means that the gain is set by the ratio of (R7 + R9) /R4. The
gain error is primarily controlled by the precision of the
resistors used. The provided resistors are a 1% tolerance
which will dominate the gain error. To reduce system gain
error, the resistors can be replaced with 0.1% resistors.
Jumper Summary
JP1: The logic supply jumper has two settings:
V+: The comparator output is tied to the V+ supply
EXT: The comparator output is tied to an external supply
on the VLOGIC turret.
Optional Settings
1. To power the LT6118 from a supply separate from the
load, remove R1 and connect the power supply to V+
turret.
2. There are a number of optional components that (not
installed) allow the DC2193 to be tailored to a specific
application:
A) To free comparator input INC for other use, remove
R7 and R9 and install R8. Connect LE turret as re-
quired.
B) To add filtering to the amplifier output, install C3.
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DEMO MANUAL DC2193A
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
schematic Diagram
5
5
4
4
3
3
2
2
1
1
D D
C C
B B
A A
TECHNOLOGY
TECHNOLOGY
TECHNOLOGY
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DEMO MANUAL DC2193A
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2014
LT 1114 • PRINTED IN USA
DEMONSTRATION BOARD IMPORTANT NOTICE
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This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
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in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
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If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
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