Datasheet

The MAX8650 can also be synchronized to an external
clock by connecting the clock signal to FSYNC. In
addition, SYNCO is provided to synchronize a second
MAX8650 controller 180° out-of-phase with the first by
connecting SYNCO of the first controller to FSYNC of
the second. When the first controller is synchronized to
an external clock, the external clock is inverted to gen-
erate SYNCO. Therefore, to get 180° out-of-phase oper-
ation, the clock input to the first controller should have
a 50% duty cycle.
Power-Good Signal (POK)
POK is an open-drain output on the MAX8650 that mon-
itors the output voltage. When the output is above 92%
of its nominal regulation voltage, POK is high imped-
ance. When the output drops below 89% of its nominal
regulation voltage, POK is internally pulled low. POK is
also internally pulled low when the MAX8650 is shut
down. To use POK as a logic-level signal, connect a
pullup resistor from POK to the logic supply rail.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa-
tion in the MAX8650. When the junction temperature
exceeds +160°C, an internal thermal sensor shuts
down the device, allowing the IC to cool. The thermal
sensor turns the IC on again after the junction tempera-
ture cools by 15°C, resulting in a pulsed output during
continuous thermal-overload conditions.
R
f
ns
k
ns
FSYNC
S
=−
⎛
⎝
⎜
⎞
⎠
⎟
⎛
⎝
⎜
⎞
⎠
⎟
1
2
162
1
16 34
Ω
.
MAX8650
4.5V to 28V Input Current-Mode Step-Down
Controller with Adjustable Frequency
______________________________________________________________________________________ 13
SYNC
EN
ON
R2
R1
R5
R6
C5
C13
R14
Q1
Q2
D2
D1
C11
C6
FSYNC
EN
POK
SYNCO
SCOMP
ILIM2
REFIN
SS
ILIM1
COMP
FB
OVP
2
4
5
6
7
8
9
10
12
14
15
13
MODE
BST
DH
LX
DL
PGND
VL
IN
AVL
CS+
CS-
GND
1
11
24
3
23
22
21
20
16
19
18
17
C9A
C9B
C14
R15
C3
V
OUT
3.3V/15A
V
IN
10V TO 24V
L1
C15
C10
C12
C7
C8
R13
R9
R10
R8
OFF
POK
SYNCO
MAX8650EEG
C2
C1
R11
R12
Figure 3. Applications Circuit with 500kHz Switching, 10V to 24V Input, and 3.3V/15A Output