LTM8026 LINER [Linear Technology], LTM8026 Datasheet - Page 18

• Manufacturer Part Number: LTM8026
• Description: 36VIN, 5A, 2-Quadrant CVCC Step-Down
• Manufacturer: LINER [Linear Technology]

LTM8052
applicaTions inForMaTion
when the input voltage exceeds some threshold. This
Figures 5a through 5c are crowbar circuits, which attempt
to prevent the input voltage from rising above some level
by clamping the input to GND through a power device. In
some cases, it is possible to simply turn off the LTM8052
is possible when the voltage power source that drives
current into V
circuit is shown in Figure 5d. When the power source on
the output drives V
the comparator pulls down on the RUN pin and stops
switching in the LTM8052. When this happens, the input
capacitance needs to absorb the energy stored within the
LTM8052’s internal inductor, resulting in an additional
voltage rise. As shown in the Block Diagram, the internal
inductor value is 2.2uH. If the LTM8052 negative current
limit is set to 5A, for example, the energy that the input
18
OUT
never exceeds V
IN
above a predetermined threshold,
Figure 5c. The SCR Latches On When the Activation Threshold is
Reached, So a Fuse or Some Other Method of Disconnecting the
Load Should be Used
Figure 5d. This Comparator Circuit Turns Off the LTM8052 if
the Input Rises Above a Predetermined Threshold. When the
LTM8052 Turns Off, the Energy Stored in the Internal Inductor
Will Raise V
10µF
IN
. An example of this
SCR
IN
a Small Amount Above the Threshold.
ZENER
DIODE
–
+
V
IN
LTM8052
REFERENCE
EXTERNAL
GND
VOLTAGE
V
RUN
IN
LTM8052
V
OUT
capacitance must absorb is 1/2 LI
the comparator circuit in Figure 5d is set to pull the RUN
pin down when V
according to the capacitor energy equation:
If the total input capacitance is 10μF, the input voltage
will rise to:
For applications where only sourcing current (one quadrant
operation) is desired, use LTM8026.
27.5µJ =
V
2
1
GND
IN
V
FUSE
C (V
OUT
= 15.2V
CURRENT
IN
CURRENT
LOAD
LOAD
SOURCING
2
SOURCING
− V
LOAD
2
1
LOAD
10µF(V
8052 F05a
TRIP
8052 F05d
TRIP
2
) = 27.5µJ
IN
= 15V. The input voltage will rise
2
− 15V
2
)
2
= 27.5μJ. Suppose
8052fa