LTC3631 Linear Technology Corporation, LTC3631 Datasheet - Page 6

• Manufacturer Part Number: LTC3631
• Description: High Voltage 100mA Synchronous Step-Down Converter
• Manufacturer: Linear Technology Corporation

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PIN FUNCTIONS
LTC3631
TYPICAL PERFORMANCE CHARACTERISTICS
SW (Pin 1): Switch Node Connection to Inductor. This
pin connects to the drains of the internal power MOSFET
switches.
V
should be tied between this pin and GND (Pin 8).
I
pin to ground sets the peak current trip threshold. Leave
fl oating 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 fl oating, 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.
100mA/DIV
6
INDUCTOR
SET
CURRENT
IN
VOLTAGE
OUTPUT
1V/DIV
(Pin 2): Main Supply Pin. A ceramic bypass capacitor
(Pin 3): Peak Current Set Input. A resistor from this
Soft-Start Waveforms
C
SS
= 0.047μF
500μs/DIV
3631 G19
50mV/DIV
50mA/DIV
CURRENT
VOLTAGE
OUTPUT
LOAD
V
V
Load Step Transient Response
IN
OUT
= 24V
= 5V
1ms/DIV
V
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): Chip Ground.
Exposed Pad (Pin 9): Ground. Must be soldered to PCB
ground for optimal electrical and thermal performance.
OUT
/V
FB
(Pin 6): Output Voltage Feedback. For the fi xed
3631 G20
100mA/DIV
INDUCTOR
CURRENT
VOLTAGE
OUTPUT
2V/DIV
Short-Circuit Response
V
V
IN
OUT
= 10V
= 5V
200μs/DIV
3631fa
3631 G21