Datasheet
MAX8655
Highly Integrated, 25A, Wide-Input,
Internal MOSFET, Step-Down Regulator
14 ______________________________________________________________________________________
Design Procedure
Setting the Output Voltage
To set the output voltage for the MAX8655, connect FB
to the center of an external resistor-divider from the out-
put to GND (R3 and R5 of Figure 5). Select R5 between
5kΩ and 24kΩ, and then calculate R3 with the following
equation:
where V
FB
= 0.7V or V
REFIN
. R3 and R5 should be
placed as close as possible to the IC.
RR
V
V
OUT
FB
35 1=× −
⎛
⎝
⎜
⎞
⎠
⎟
MAX8655
PVIN
PVIN
PVIN
PVIN
PVIN
LX
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
LX
LX
LX
LX
LX
OFF
ON
PVIN
C14
1µF
C8
0.22µF
C10
100pF
C12
560pF
C13
0.022µF
C15
0.22µF
C1–C5
5 x 10µF
CERAMIC
C16
0.22µF
R1
1.74kΩ
R4
11.5kΩ
R3
11.5kΩ
R2
3.57kΩ
R9
71.5kΩ
R7
243kΩ
R6
3.09kΩ
L1
1µH
1.6mΩ
C18
2.2µF
R8
76.8kΩ
R13
100kΩ
R14
13kΩ
R11
140kΩ
C9
0.22µF
ENABLE
INPUT
INPUT 6V TO 20V
FOR INTERNAL
OSCILLATOR
OPERATION ONLY
POWER-OK OUTPUT
FSYNC INPUT
SYNC OUTPUT
OUTPUT 3.3V
UP TO 20A
AVL
AVL
D1
VL
AVL
LX
VLGND
GND
VL
IN
EN
AVL
GND
SCOMP
ILIM2
REFIN
SS
COMP
FB
OVP
ILIM1
CS-
CS+
N.C.
N.C.
PVIN
PVIN
PVIN
PVIN
PVIN
PVIN
LXB
N.C.
GND
BST
SYNCO
MODE
FSYNC
POK
GND
R12
10kΩ
C6–C19
3 x 220µF
15µΩ ESR
R5
3.09kΩ
Figure 4. Single-Phase, 350kHz Switching, 6V to 20V Input, and 3.3V/20A Output
MAX8655
LX
R5
R3
FB
Figure 5. Setting the Output Voltage with a Resistor Voltage-
Divider