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dc2392af
DEMO MANUAL DC2392A
Description
LTC7860
High Voltage Switching
Surge Stopper
Demonstration circuit 2392A is a high efficiency switching
surge stopper featuring the
LTC
®
7860
. The board operates
from an input range of 7V to 100V, and provides a 7V to
34V output at 0A to 10A. Its output is current limited. A
soft-start feature controls output voltage slew rate at start-
up, reducing current surge and voltage overshoot. The
demonstration board includes an optional reverse polarity
protection MOSFET and has options for an input filter and
diode to attenuate spikes. For a lower output voltage limit
of less than 12V, there is an optional feedback circuit.
The LTC7860 high efficiency surge stopper protects loads
from high voltage transients. High efficiency compared to
linear circuits permits higher currents and smaller solution
sizes. During an input overvoltage event, such as a load
dump in vehicles, the LTC7860 controls the gate of an
external MOSFET to act as a switching DC/DC regulator
(PROTECTIVE PWM mode). This operation regulates the
output voltage to a safe level, allowing the loads to oper-
ate through the input overvoltage event. During normal
operation (SWITCHON mode), the LTC7860 turns on the
external MOSFET continuously, passing the input voltage
through to the output. An internal comparator limits 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
voltage across the current sense resistor and regulates the
maximum output current to protect against overcurrent
faults. An adjustable timer limits the time that the LTC7860
can spend in overvoltage or overcurrent regulation. When
the timer expires, the external MOSFET is turned off until
the LTC7860 restarts after a cool down period. By strictly
limiting the time in PROTECTIVE PWM mode when the
power loss is higher, the components and thermal design
can be optimized for normal operation and safely oper-
ate through high voltage input surges and/or overcurrent
faults. This demo board takes advantage of the LTC7860’s
V
IN
-centric PMOS architecture to float the control ground
allowing operation beyond the controller’s 60V rating.
This board is suitable for a wide range of automotive,
military, telecom, industrial, and other applications. The
LTC7860 is available in a small 12-pin thermally enhanced
MSOP package. For other output requirements, see the
LTC7860 data sheet or contact the LTC factory.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2392A
Specifications are at T
A
= 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input Supply Range
Normal Operation
7
32
V
500ms Ride-Through
7
100
V
DC Survival
0
100
V
V
OUT
Output Voltage
7
28
35
V
I
OUT
Output Current Range, continuous
Free Air
0
10
A
I
LIMIT
Current Limit
V
IN
= 28V
13
A
I
LIMIT
Current Limit
V
IN
= 40V
10.5
A
V
IN
-V
OUT
Insertion Loss
V
IN
= 28V, I
OUT
= 10A
400
mV
F
SW
Switching (Clock) Frequency
350
kHz
T
PWM
PROTECTIVE PWM Mode Time Limit
V
IN
> 35V
0.85
1.06
1.24
s
V
OUT P-P
Output Ripple
V
IN
= 40V, V
OUT
= 17.2V, I
OUT
= 5A (20MHz BW)
100
mV
P–P
Approximate Size
Component Area x Top Component Height
35 × 42 × 10
mm
