DC2193A - Demo Manual

DEMO MANUAL DC2193A
LT6118
High Side Current Sense Amplifier with Reference
and Comparator with POR Capability
Description
Demonstration circuit 2193A features the LT®6118, a
high side current sense amplifier with a comparator and
a 400mV reference.
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 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 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
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
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
Specifications are at TA = 25°C
SYMBOL
PARAMETER
CONDITIONS
VIN
Input Supply Range
MIN
TYP
2.7
MAX
60
UNITS
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
IQ
VIN Quiescent Current
VIN = 12V
800
µA
VTHR
Comparator Threshold
VIOUT = 1.25V
500
mA
4
A
Operating Principles
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 guarantee 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.
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DEMO MANUAL DC2193A
Block Diagram
7
V+
100Ω
8
1
SENSEHI
3k
SENSELO
3k
V–
34V
–
6V
+
OUTA
V–
V+
6
V–
100nA
2
LE
V+
+
V–
4
2
INC
–
3
OVERCURRENT FLAG
OUTC
5
400mV
REFERENCE
V–
6118 F01
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DEMO MANUAL DC2193A
Quick Start Procedure
The DC2193A provides a simple way to evaluate the performance of the LT6118. Refer to Figure 1 for proper measurement equipment setup and follow these procedures:
3.Connect a load to the demo boards OUT terminal (positive) and ground. The load may be a power resistor,
active load instrument or a circuit of interest.
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.
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
2.Connect a DMM or oscilloscope to the IOUT with the
common connection connected to ground.
5.Measure the output voltage and confirm that it corresponds 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.
RESET
20.0
0.25V
0.10A
LOAD
Figure 1
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DEMO MANUAL DC2193A
Operation
Current Sense Gain
Optional Settings
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.
1.To power the LT6118 from a supply separate from the
load, remove R1 and connect the power supply to V+
turret.
Jumper Summary
JP1: The logic supply jumper has two settings:
V+: The comparator output is tied to the V+ supply
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 required.
B)To add filtering to the amplifier output, install C3.
EXT: The comparator output is tied to an external supply
on the VLOGIC turret.
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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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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TECHNOLOGY
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DEMO MANUAL DC2193A
Schematic Diagram
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DEMO MANUAL DC2193A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
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
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
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
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR
ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LTC from all claims
arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.
LTC currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.
Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
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