DC2261A - Demo Manual

DEMO MANUAL DC2261A
High Side Current Sense
with Comparators and a
400mV Reference
Description
Demonstration circuit 2193A features the LT®6119, 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 latching 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
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
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
CONDITIONS
SYMBOL
PARAMETER
VIN
Input Supply Range
MIN
TYP
VOUTA
Measured Output Signal
ILOAD = 100mA
ILOAD
Output Load Current Range
Thermal Limit of RSENSE
IQ
IN Quiescent Current
VIN = 12V
600
µA
ITHR1
Comparator1 Threshold
VOUTA = 3V
300
mA
ITHR2
Comparator2 Threshold
VOUTA = 0.5V
50
mA
2.7
MAX
60
1
UNITS
V
V
3
A
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.
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DEMO MANUAL DC2261A
Block Diagram
LT6119-1
9
V+
100Ω
10
1
SENSEHI
3k
SENSELO
3k
6V
+
OUTA
8
V–
V–
V+
V–
34V
–
100nA
2
LE
V+
INC2
+
3
UNDERCURRENT FLAG
OUTC2
7
–
V–
400mV
REFERENCE
V+
+
4
OVERCURRENT FLAG
OUTC1
INC1
6
–
V–
5
LT6119-2
9
V+
100Ω
10
1
SENSEHI
3k
SENSELO
3k
V–
34V
–
6V
+
OUTA
V
V–
V+
8
–
100nA
2
LE
V+
INC2
–
3
OUTC2
OVERCURRENT FLAG
7
+
V–
400mV
REFERENCE
V+
OUTC1
+
4
OVERCURRENT FLAG
INC1
6
–
V–
5
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DEMO MANUAL DC2261A
Quick Start Procedure
With the demonstration circuit, it is easy to set up and
evaluate the performance of the LT6119. Refer to Figure 1
for proper measurement equipment setup and follow the
procedure below:
1. With the power off, connect the power supply positive
to IN and the common to GND. With default 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. Connect a load to the demo board OUT terminal (positive) and ground. The load may be a power resistor,
active load instrument or a circuit of interest.
5. Measure the output voltage and confirm that it corresponds to the load current. VOUTA (V) = 10 • ILOAD(A)
for the factory installed resistors.
6. If able, sweep load current from 0A to 300mA to verify
the operation of the comparators. Use the reset push
button to reset latched comparator outputs.
2. Connect a voltmeter or oscilloscope to the OUTA with
the common input connected to ground.
3. Turn on the power supply. The comparator outputs
start in a known state as shown in the following table
if there is no load attached.
PART
OUTC1
OUTC2
DC2261A-A LT6119-1
High
Low
DC2261A-B LT6119-2
High
High
200Ω
Figure 1. Test Setup
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DEMO MANUAL DC2261A
Current Sense Gain
The gain of the LT6119 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 (ROUT)/R4,
where ROUT = (R7 + R10 + R11) || R8(OPT). The default
values are R7 = 2k, R10 = 6.65k, R11 = 1.33k, and R8 is not
installed. This provides a gain of 9.98k/100. By installing
the optional resistor, R8, the gain can be reduced. The gain
error is primarily set 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
Optional Settings
1.To power the LT6119 from a supply separate from the
load, remove R1 and connect the power supply to the
V+ turret.
2.There are a number of optional components that allow
the DC2193 to be tailored to a specific application:
A) To free comparator inputs INC1 and INC2 for other
use, remove R7, R10 and R11 and install R8. Connect LE turret as required.
B) To add filtering to the amplifier output, install C3.
C) If driving the LE turret from an external source,
pressing the reset button, SW1 will short the signal.
A resistor can be added at R13 to help isolate the
external signal.
- 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.
A
B
C
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1
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
TECHNOLOGY
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5
A
B
C
D
DEMO MANUAL DC2261A
Schematic Diagram
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DEMO MANUAL DC2261A
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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Linear Technology Corporation
LT 0115 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
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●
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