lt3663 Linear Technology Corporation, lt3663 Datasheet - Page 5

• Manufacturer Part Number: lt3663
• Description: 1.2a, 1.5mhz Step-down Switching Regulator With Output Current Limit
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
V
internal regulator and internal power switch. Capacitively
bypass the pin to ground.
RUN (Pin 2): The Run pin is used to put the LT3663 into
shutdown mode. Tie to ground to shut down the LT3663.
Tie to 2.5V or more for normal operation. If the shutdown
feature is not used, connect this pin to V
FB (Pin 3): The LT3663 regulates the FB pin to 0.8V. Con-
nect the feedback resistor divider tap to this pin.
I
a resistor to ground to program the regulator output cur-
rent limit.
V
minal of the internal output current limit sense resistor.
FUNCTIONAL BLOCK DIAGRAM
LIM
OUT
IN
V
C1
IN
(Pin 1): The V
R
(Pin 4): Output Current Limit Program Pin. Connect
ILIM
(Pin 5): The V
V
RUN
I
LIM
IN
IN
OUT
2.5V INTERNAL
UVLO AND OVP
pin supplies current to the LT3663’s
REGULATOR,
REFERENCE,
pin is connected to the negative ter-
R
SENSE1
COMPENSATION
V
C
INTERNAL
–
+
A1
COMPENSATION
IN
.
SLOPE
OSCILLATOR
EXPOSED PAD (GND)
+
–
I
internal output current limit sense resistor. The I
is also the anode to the internal BOOST diode.
BOOST (Pin 7): The BOOST pin is used to provide a drive
voltage, higher than the input voltage, to the internal power
switch. The BOOST pin is also internally connected to the
cathode of the BOOST diode.
SW (Pin 8): The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
Exposed Pad (Pin 9): Ground. The Exposed Pad must be
soldered to the PCB and electrically connected to ground.
Use a large ground plane and thermal vias to optimize
thermal performance.
SENSE
R
S
G2
G1
(Pin 6): The I
Q
–
+
–
+
0.8V
SENSE
DRIVER
+
–
pin is the positive input to the
Q1
R
SENSE2
BOOST
I
SENSE
D2
V
OUT
SW
FB
3663 BD
R1
R2
C3
LT3663
C2
SENSE
D1
V
OUT
3663fa
5
pin
L