Datasheet

LTC3631
6
3631fe
For more information www.linear.com/LTC3631
pin FuncTions
SW (Pin 1): Switch Node Connection to Inductor. This
pin connects to the drains of the internal power MOSFET
switches.
V
IN
(Pin 2): Main Supply Pin. A ceramic bypass capacitor
should be tied between this pin and GND (Pin 8).
I
SET
(Pin 3): Peak Current Set Input. A resistor from this
pin to ground sets the peak current trip threshold. Leave
floating for the maximum peak current (225mA). Short
this pin to ground for the minimum peak current (50mA).
A 1µA current is sourced out of this pin.
SS (Pin 4): Soft-Start Control Input. A capacitor to ground
at this pin sets the ramp time to full current output dur
-
ing start-up. A 5µA current is sourced out of this pin. If
left floating, the ramp time defaults to an internal 0.75ms
soft-start.
RUN (Pin 5): Run Control Input. A voltage on this pin
above 1.2V enables normal operation. Forcing this pin
below 0.7V shuts down the LTC3631, reducing quiescent
current to approximately 3µA.
V
OUT
/V
FB
(Pin 6): Output Voltage Feedback. For the fixed
output versions, connect this pin to the output supply. For
the adjustable version, an external resistive divider should
be used to divide the output voltage down for comparison
to the 0.8V reference.
HYST (Pin 7): Run Hysteresis Open-Drain Logic Output.
This pin is pulled to ground when RUN (Pin 5) is below
1.2V. This pin can be used to adjust the RUN pin hysteresis.
See Applications Information.
GND (Pin 8, Exposed Pad Pin 9):
Ground. The exposed
pad must be soldered to the printed circuit board ground
plane for optimal electrical and thermal performance.
Typical perForMance characTerisTics
Soft-Start Waveform Load Step Transient Response Short-Circuit Response
OUTPUT
VOLTAGE
1V/DIV
5ms/DIVC
SS
= 0.047µF
3631 G19
OUTPUT
VOLTAGE
50mV/DIV
LOAD
CURRENT
50mA/DIV
1ms/DIV
3631 G20
V
IN
= 24V
V
OUT
= 5V
OUTPUT
VOLTAGE
2V/DIV
INDUCTOR
CURRENT
100mA/DIV
200µs/DIV
3631 G21
V
IN
= 10V
V
OUT
= 5V