Analog Devices Linear ADI Power LTC4249 Quick setup guide

1
DEMO MANUAL DC2733A
Rev. 0
DESCRIPTION
LTC4249
65V Dual Electronic Circuit Breaker
with Current Monitors
The DC2733 is a demonstration system for the LTC
®
4249,
65V Dual Electronic Circuit Breaker with Current Monitors.
The LTC4249 provides dual independent 1.2A, 75mΩ
circuit breakers that can function independently or work
together in parallel. Each circuit breaker channel has its
own enable, ready, and IMON pins.
The DC2733 demo board gives access to both channels of
the LTC4249, including the independent RDY and IMON
outputs and the EN inputs. Resistors at the IMON pins set
the circuit breaker thresholds as well as the IMON current-
to-voltage gains. The IC draws power from the IN1 input.
All registered trademarks and trademarks are the property of their respective owners.
BOARD PHOTO
DC2733 Board Features
• Demonstrate dual LTC4249 circuit breaker channels
• Monitor each channel current with IMON
• Gang multiple parallel channels for larger currents
• Convenient on-board pushbutton enable control
DC2733 Hardware Required
• DC2733 board
• Input power supply between 6V and 65V
•Two 1.2A loads
Design files for this circuit board are available.
LED INDICATORS
SIGNAL ACCESS TURRETS
ON/OFF PUSHBUTTON
ENABLE JUMPERS

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DEMO MANUAL DC2733A
Rev. 0
PERFORMANCE SUMMARY
Specifications are at TA= 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
IN1 and OUT1 Operating Voltage Range Referenced to GROUND 6 65 V
IN2 and OUT2 Operating Voltage Range (1) Referenced to GROUND 1.5 65 V
(INn- OUTn) Channel off.
Reverse voltage not permitted.
0 65 V
INnForward Current Forward current flows from INnto OUTn0 1.2 A
INn Reverse Current (2) Reverse current flows from OUTnto INn –1.2 0 A
CHnSwitch Resistance while On Channel enabled 75 150 mΩ
CHnSwitch Resistance while Off 300 kΩ
Circuit Breaker Response Time (1x OC) VIMON > 1.2V 60 μs
IMON Output Current Accuracy (3) IOUT = 1.0A –3 3 %
Circuit Breaker Threshold Accuracy 1x threshold –2.5 2.5 %
(1) IN2 may be tied to GND if unused.
(2) Reverse current is only permitted when the channel is on. An internal diode from OUTnto INnwill forward bias if OUTnvoltage is above INn.
(3) IMON does not register reverse current. The circuit breaker will not respond to reverse current.

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DEMO MANUAL DC2733A
Rev. 0
QUICK START PROCEDURE
The LTC4249 is a positive voltage circuit breaker. It has
two independent 75mΩ switches that turn on when their
associated ENnpin is high, and turn off either when ENn
is lowered or when the forward current causes the voltage
at the IMON pin to exceed 1.2V. On the DC2733 demo
board, each hardware channel is independent, with an
input port, INn, and an output port, OUTn. Current flow-
ing from IN to OUT is positive. Voltage at both the input
and output pins must remain between 0V and 65V with
respect to GROUND. Each channel’s input-to-output volt-
age must remain positive:(VIN – VOUT) > 0.0V. A reverse
biased channel will conduct reverse current, even when
the circuit breaker is off, due to an internal diode across
the circuit breaker switch. Both circuit breaker channels
may be shorted together and used in parallel to increase
current carrying capacity.
An enabled circuit breaker output indicates ready with the
RDYnpin. Each circuit breaker channel operates indepen-
dently. Reset a circuit breaker channel by lowering and
raising its ENninput.
Please read the LTC4249 datasheet for more information.
On the DC2733A board there are two configuration jump-
ers that connect the ENninputs of the IC to the pushbutton
ON/OFF switch. The default jumper settings are suitable
for both channels activated together by the pushbutton.
The pushbutton uses an LTC2954 pushbutton control-
ler that is powered by an on-board auxillary 3.3V power
domain. The 3.3V power rail is produced from IN1 by an
LT3010 linear regulator. Refer to the board schematics
for details.
Table1. Jumper Summary
JUMPER SETTING COMMENT
EN1
(J7)
Connected
(DEFAULT)
The LTC4249 EN1 input is connected to
the pushbutton ON/OFF switch.
Removed The LTC4249 EN1 input is floating and
may be driven externally. **
EN2
(J6)
Connected
(DEFAULT)
The LTC4249 EN2 input is connected to
the pushbutton ON/OFF switch.
Removed The LTC4249 EN2 input is floating and
may be driven externally. **
ENABLE
(SWO)
Pushbutton toggle Enable/disable the ENnpins.
** LTC4249 ENninputs have internal pull-up currents to INTVCC.
The LEDs on the board indicate the state of the ENnpins,
the RDYnpins, and the 3.3V auxillary power rail.
LED Function
EN1
(LED4)
Illuminates green when the EN1 pin of the
LTC4249 is high (active).
EN2
(LED5)
Illuminates green when the EN2 pin of the
LTC4249 is high (active).
RDY1
(LED2)
Illuminates green when the RDY1 pin of
the LTC4249 is high (active).
RDY2
(LED1)
Illuminates green when the RDY2 pin of
the LTC4249 is high (active).
V3.3
(LED3)
Illuminates green when the V3.3 power
rail is active (powered by IN1).

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DEMO MANUAL DC2733A
Rev. 0
+
-
SOURCE
KELVIN
GROUND
CURRENT
FLOW
LOAD 1
LOAD 2
Figure1. Source and Load Connections. Current Return Outside
of Board.
Connect input power supplies to IN1 and IN2 inputs, and
connect independent loads to OUT1 and OUT2 ports, as in
Figure1. The same input supply may connect to both IN1
and IN2. The LTC4249 draws power from the IN1 port,
so powering IN1 is a minimal requirement. Driving IN2
is optional. If channel 2 is unused tie IN2 to GND. OUT2
may be left floating.
The board has several connections labeled GROUND.
When connecting power supplies and loads, the cur-
rents naturally flow from INnpins, through the LTC4249,
then out through the OUTnpins. On the current return
path, however, it is best to avoid ground currents flowing
through the GROUND plane of the demo board. Instead,
connect a single wire from ground near the power sup-
plies to one of the GROUND connections on the board,
forming a Kelvin connection back to the system ground
point. This avoids load currents flowing through the
GROUND plane on the board. See Figure1.
In the configuration of Figure1 when the forward cur-
rent through CH1 exceeds the programmed circuit breaker
threshold the channel will turn off. The current through
CH2 will be unaffected. Re-enable a channel by toggling
ENn.
QUICK START PROCEDURE
It is also possible to use channels in parallel, as shown in
Figure2. Channels will share current, but remember that
channel impedances are not perfectly matched, so cur-
rents will share slightly unevenly. When the circuit breaker
trips it will trip in one channel first, followed quickly by
the other channel, usually within about 20μs.
+
-
SOURCE
KELVIN
GROUND
CURRENT
FLOW
LOAD
Figure2. Parallel Channel Operation
A transient fault will trip the circuit breaker then allow the
LTC4249 to restart after the retry interval. A fault lasting
longer than 3 seconds (3 retries) will result in a persistent
off condition. Clear a faulted channel by toggling ENnlow
then high.
The demo board has 10kΩ resistors at both of the IMON
pins. This is the recommended value to give a circuit
breaker current threshold of 1.2A (1.2V on IMON). While
10kΩ is the smallest recommended resistor value, it is
possible to replace R1 and R2 on the board with larger
valued resistors to lower the circuit breaker current
threshold. The relationship between resistance and CB
threshold is:
ICB =1.2 •
R
IMON
10000
⎛
⎝
⎜⎞
⎠
⎟
(1)
Note that circuit breaker accuracy is directly related to the
accuracy of R1 and R2. We use 0.1% resistor tolerance
for best results.

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DEMO MANUAL DC2733A
Rev. 0
In addition to controlling the circuit breaker, the IMON pins
can be used by an external circuit to read channel current.
The IMON pin voltage represents the current flowing in
its channel. Attach a voltage meter or ADC to each IMON
pin as shown in Figure3.
+
-
SOURCE
KELVIN
GROUND
CURRENT
FLOW
LOAD 1
LOAD 2
IMON 2
IMON 1
(1.2 V/A)
(1.2 V/A) V
V
Figure3. IMON Current Monitoring
Each LTC4249 channel switch has a body diode that will
conduct in the OUT-to-IN direction if voltage is reversed.
For this reason V(OUT) must always be less than or equal
to V(IN). To prevent potential backward flowing current
use two switches in series, back-to-back, as shown in
Figure4. In this case the return current necessarily flows
externally to the board, but the Kelvin GND connection is
still required.
+
-
SOURCE
LOAD
Figure4. Series Switches to Eliminate Potential Reverse Current
QUICK START PROCEDURE

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DEMO MANUAL DC2733A
Rev. 0
SCHEMATIC DIAGRAM

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DEMO MANUAL DC2733A
Rev. 0
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Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
SCHEMATIC DIAGRAM

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DEMO MANUAL DC2733A
Rev. 0
 ANALOG DEVICES, INC. 2021
05/21
www.analog.com
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circuitry, damage may occur on devices subjected to high energy ESD. Therefore, proper ESD precautions should be taken to avoid performance degradation or loss of functionality.
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