Datasheet

LTC3809
21
3809fc
APPLICATIONS INFORMATION
PC Board Layout Checklist
When laying out the printed circuit board, use the following
checklist to ensure proper operation of the LTC3809.
• The power loop (input capacitor, MOSFET, inductor,
output capacitor) should be as small as possible and
isolated as much as possible from LTC3809.
• Put the feedback resistors close to the V
FB
pins. The I
TH
compensation components should also be very close
to the LTC3809.
• The current sense traces should be Kelvin connections
right at the P-channel MOSFET source and drain.
• Keeping the switch node (SW) and the gate driver nodes
(TG, BG) away from the small-signal components, es-
pecially the feedback resistors, and I
TH
compensation
components.
10μF
s2
V
IN
2.75V TO 8V
V
OUT
2.5V
(5A AT 5V
IN
)
MP
Si7540DP
MN
Si7540DP
3809 F10
2
1
6
4
3
9
8
10
7
5
11
L
1.5μH
R
ITH
15k
187k
59k
L: VISHAY IHLP-2525CZ-01
C
OUT
: SANYO 4TPB150MC
C
ITH
220pF
100pF
C
OUT
150μF
SYNC/MODE
V
IN
PLLLPF
IPRG
I
TH
V
FB
TG
SW
BG
RUN
GND
LTC3809EDD
+
10μF
s2
V
IN
2.75V TO 8V
V
OUT
1.8V
(5A AT 5V
IN
)
MP
Si7540DP
MN
Si7540DP
D
OPT
3809 F11
2
1
6
4
3
9
8
10
7
5
11
10k
L
1.5μH
15k
118k
100pF
59k
L: VISHAY IHLP-2525CZ-01
D: ON SEMI MBRM120L (OPTIONAL)
470pF
100pF
10nF
C
OUT
22μF
s2
SYNC/MODE
V
IN
PLLLPF
IPRG
I
TH
V
FB
TG
SW
BG
RUN
GND
LTC3809EDD
Figure 11. Synchronizable DC/DC Converter with Ceramic Output Capacitors
Figure 10. 550kHz, Synchronizable DC/DC Converter with Internal Soft-Start