MAX8686 Maxim Integrated Products, MAX8686 Datasheet - Page 14

• Manufacturer Part Number: MAX8686
• Description: DC-DC Converter Delivers Up To 25A Per Phase
• Manufacturer: Maxim Integrated Products

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Single/Multiphase, Step-Down,
DC-DC Converter Delivers Up to 25A Per Phase
The MAX8686 provides output overvoltage protection
(OVP). The OVP threshold is set at 20% above the set
output voltage. When the overvoltage condition is expe-
rienced, the output is latched to PGND through the low-
side MOSFET. To clear the latch, the EN/SLOPE input
should be pulled logic-low and then reinitialized. The
output starts up in a soft-start mode. To prevent the
overvoltage protection from initializing during power-up,
some consideration should be given to the soft-start
timing to reduce the inrush current. In addition, the
proper compensation network would prevent overshoot
during power-up.
Figure 2. Single-Phase Application Circuit Operating at V IN = 12V
14
______________________________________________________________________________________
ENABLE
POWER-
(EN)
115kΩ
R4
10nF
2.2nF
OK
C3
10kΩ
C4
R1
150pF
GFREQ
C4
5.6kΩ
R5
162kΩ
LX
R16
150kΩ
200kΩ
15pF
R2
R3
C2
C17
1µF
0.22µF
330pF
C18
C1
31
32
33
34
35
36
37
38
39
40
Overvoltage Protection
BST
POK
FREQ
SS
ILIM
REFIN
PHASE/REFO
COMP
RS+
RS-
10Ω
+
R13
0.22µF
C16
GFREQ
C15
0.1µF
LX
10Ω
R12
MAX8686
U1
POK is an open-drain output that monitors the output volt-
age. When the output is above 90% of its nominal regula-
tion voltage, POK goes high impedance. There is a 3%
hysteresis to prevent the POK output from chattering. The
POK indicator can be used for sequencing.
Thermal-overload protection limits total power dissipa-
tion in the MAX8686. When the junction temperature
exceeds +160°C, an internal thermal sensor shuts
down the device, allowing it to cool down. The thermal
sensor turns the device on again after the junction tem-
perature cools by 30°C, resulting in a pulsed output
during continuous thermal-overload conditions. See
Figures 2, 3, and 4.
PGND
PGND
PGND
PGND
PGND
N.C.
LX
IN
IN
IN
20
19
18
17
16
15
14
13
12
11
Thermal-Overload Protection
270Ω
R11
C13
10µF
0.56µH
L11
Power-OK (POK) Signal
C12
10µF
270Ω
R14
C14
1µF
C11
10µF
6V TO 20V
INPUT
C6
220µF
C7
220µF
1.2V/25A
OUTPUT