Linear LTC7860 Demo Manual

Description
Demonstration circuit 2392A is a high efficiency switching
surge stopper featuring the
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

performance summary

SYMBOL PARAMETER
V Input Supply Range
IN
V Output Voltage
OUT
I Output Current Range, continuous
OUT
I Current Limit
LIMIT
I Current Limit
LIMIT
V -V Insertion Loss
IN OUT
F Switching (Clock) Frequency
SW
T PROTECTIVE PWM Mode Time Limit
PWM
V Output Ripple
OUT P-P
Approximate Size
LTC 7860. The board operates
®
Specifications are at T
CONDITIONS
Normal Operation
500ms Ride-Through
DC Survival
Free Air
V = 28V
IN
V = 40V
IN
V = 28V, I
IN OUT
V > 35V
IN
V = 40V, V
IN
Component Area x Top Component Height
DEMO MANUAL DC2392A
High Voltage Switching
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 -centric PMOS architecture to float the control ground
IN
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
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.
= 25°C
A
= 10A
= 17.2V, I = 5A (20MHz BW)
OUT OUT
LTC7860
Surge Stopper
MIN TYP MAX
7 32
7 100
0 100
7 28 35
0 10
13
10.5
400
350
0.85 1.06 1.24
100
35 × 42 × 10
UNITS
V
V
V
V
A
A
A
mV
kHz
s
mV
P–P
mm
dc2392af
1