lt3465a Linear Technology Corporation, lt3465a Datasheet - Page 12

• Manufacturer Part Number: lt3465a
• Description: 2.4mhz White Led Step-up Converters With Built-in Schottky In Thinsot
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
LT3465/LT3465A
12
Open-Circuit Protection
The LT3465 and LT3465A have an internal open-circuit
protection circuit. In the cases of output open circuit,
when the LEDs are disconnected from the circuit or the
LEDs fail, the V
LT3465A will then switch at a very low frequency to
minimize the input current. V
output open circuit are shown in the Typical Performance
Characteristics.
Board Layout Consideration
As with all switching regulators, careful attention must be
paid to the PCB board layout and component placement.
To maximize efficiency, switch rise and fall times are
made as short as possible. To prevent electromagnetic
interference (EMI) problems, proper layout of the high
frequency switching path is essential. Place C
the V
the switching regulator to minimize interplane coupling.
In addition, the ground connection for the feedback
OUT
Figure 8. Recommended Component Placement.
and GND pins. Always use a ground plane under
C
OUT
OUT
R
FB
U
is clamped at 30V. The LT3465 and
1
2
3
U
OUT
6
5
4
and input current during
L
W
3465A F08a
C
IN
GND
V
CTRL
IN
OUT
U
next to
resistor R1 should be tied directly to the GND pin and not
shared with any other component, ensuring a clean, noise-
free connection. Recommended component placement is
shown in Figure 8.
Start-Up Input Current (LT3465A)
As previously mentioned, the LT3465A does not have an
internal soft-start circuit. Inrush current can therefore rise
to approximately 400mA as shown in Figure 9 when
driving 4 LEDs. The LT3465 has an internal soft-start
circuit and is recommended if inrush current must be
minimized.
200mV/DIV
200mV/DIV
2V/DIV
CTRL
FB
I
IN
Figure 9.
50µs/DIV
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