Datasheet

MAX8650
4.5V to 28V Input Current-Mode Step-Down
Controller with Adjustable Frequency
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Pin Description (continued)
PIN NAME FUNCTION
17 OVP
Output Voltage Sensing for Overvoltage Protection. Connect OVP to the center of a resistor-divider
from OUT to GND to set the FB independent output overvoltage trip point. Connect OVP to FB if this
independence is not desired. The OVP threshold is 115% of the nominal FB regulation voltage.
18 FB
Feedback Input. Connect FB to the center of a resistor voltage-divider between the output and GND
to set the output voltage. The FB threshold regulates at 0.7V or V
REFIN
.
19 COMP
Loop Compensation. Connect COMP to an external RC network to compensate the loop. COMP is
internally pulled to GND through 20Ω during shutdown.
20 SS
Soft-Start. Connect a 0.1µF to 1µF ceramic capacitor from SS to GND. This capacitor sets the soft-
start period during startup. SS is internally pulled to GND through 20Ω during shutdown.
21 REFIN
External Reference Input. Connect REFIN to AVL to use the internal 0.7V reference for the feedback
threshold.
22 ILIM2
P r og r am m ab l e C ur r ent- Li m i t Inp ut for the Low - S i d e M OS FE T ( LX - P G N D ) . C onnect a r esi stor fr om ILIM 2
to GN D to set the val l ey cur r ent- l i m i t thr eshol d . ILIM 2 sour ces 5µA thr oug h the r esi stor , and the vol tag e
at ILIM 2 i s attenuated 5:1 to set the fi nal cur r ent l i m i t. For exam p l e, a 50kΩ r esi stor r esul ts i n 250m V at
ILIM 2. Thi s r esul ts i n a cur r
ent- l i m i t thr eshol d ( V
L X
- V
P GN D
) of 50m V . V
I LI M 2
m ust not exceed 1V .
23 SCOMP
Programmable Slope-Compensation Input. The slope-compensation voltage rate is the voltage at
SCOMP times 0.1 divided by the oscillator period (T). Connect SCOMP to AVL or GND to set to the
default of 250mV/T or 125mV/T, respectively.
24 POK
Open-Drain Output that Is High Impedance when the Output Voltage Rises Above 92% of the
Nominal Regulation Value. POK pulls low during shutdown and when the output drops below 88% of
the nominal regulation value.