LTC1265 LINER [Linear Technology], LTC1265 Datasheet - Page 10

• Manufacturer Part Number: LTC1265
• Description: 1.2A, High Efficiency Step-Down DC/DC Converter
• Manufacturer: LINER [Linear Technology]

LTC1265/LTC1265-3.3/LTC1265-5
APPLICATIONS
10
Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1265. These items are also illustrated graphically in
the layout diagram of Figure 5. Check the following in your
layout:
1. Are the signal and power grounds segregated? The
2. Does the (+) plate of the C
3. Is the input decoupling capacitor (0.1 F) connected
LTC1265 signal ground (Pin 11) must return to the (–)
plate of C
anode of the Schottky diode, and the (–) plate of C
whose leads should be as short as possible.
(Pins 1,13) as close as possible? This capacitor pro-
vides the AC current to the internal P-channel MOSFET
and its driver.
closely between power V
ground (Pin 12)? This capacitor carries the high fre-
quency peak currents.
OUT
. The power ground (Pin 12) returns to the
U
1k
3900pF
INFORMATION
U
IN
IN
1000pF
Figure 5. LTC1265 Layout Diagram (See Board Layout Checklist)
connect to the power V
(Pins 1,13) and power
W
1
2
3
4
5
6
7
PWR V
V
LB
LB
C
I
SENSE
TH
IN
T
OUT
IN
–
IN
LTC1265
1000pF
U
N/C (V
PWR V
SENSE
PGND
SGND
SHDN
SW
FB
IN
IN
IN
+
)
,
14
13
12
11
10
9
8
4. Is the Schottky diode closely connected between the
5. Does the LTC1265 SENSE
6. Are the SENSE
7. Is SHDN (Pin 10) actively pulled to ground during
SHDN
WITH ADJUSTABLE VERSION ONLY
power ground (Pin 12) and switch (Pin 14)?
close to R
applications, the resistive divider, R1 and R2, must be
connected between the (+) plate of C
ground.
minimum PC trace spacing? The 1000pF capacitor
between Pins 7 and 8 should be as close as possible to
the LTC1265.
normal operation? The SHDN pin is high impedance
and must not be allowed to float.
OUTPUT DIVIDER REQUIRED
+
C
IN
V
SENSE
IN
R1
R2
–
and the (+) plate of C
and SENSE
D1
+
0.1 F
C
OUT
LTC1265 F05
–
+
(Pin 7) connect to a point
leads routed together with
BOLD LINES INDICATE
HIGH PATH CURRENTS
R
L
SENSE
V
OUT
OUT
OUT
? In adjustable
and signal