LT3479
5
3479fc
PIN FUNCTIONS
SW (Pins 1, 2/Pins 1, 2): Switch Pins. Collector of the
internal NPN power switch. Connect the inductor and diode
here and minimize the metal trace area connected to this
pin to minimize electromagnetic interference.
L (Pin 3/Pin 3): Inductor Pin. Connect the inductor to
this pin.
V
S
(Pin 4/Pin 4): Inductor Supply. Must be locally bypassed.
Powers the switch and the inductor. In case only one supply
voltage is available, tie V
IN
and V
S
together.
V
IN
(Pin 5/Pin 5): Input Supply. Must be locally bypassed.
Powers the internal control circuitry.
R
T
(Pin 6/Pin 6): Timing Resistor Pin. Adjusts the switch-
ing frequency. Do not leave this pin open. See Table 4 for
R
T
values and switching frequencies.
SHDN (Pin 7/Pin 7): Shutdown. Tie to 1.5V or greater to
enable the device. Tie below 0.3V to turn off the device.
V
REF
(Pin 8/Pin 9): Bandgap Voltage Reference. Internally
set to 1.235V. Connect this pin to FBP if generating a posi-
tive output, or to an external resistor divider if generating a
negative voltage. This pin can provide up to 100μA of current
and can be locally bypassed with a 100pF capacitor.
FBP (Pin 9/Pin 10): The Noninverting Input to the Error
Amplifi er. Connect resistive divider tap here for negative
output voltage.
FBN (Pin 10/Pin 11): The Inverting Input to the Error
Amplifi er. Connect resistive divider tap here for positive
output voltage.
V
C
(Pin 11/Pin 12): Compensation Pin for Error Amplifi er.
Connect a series RC from this pin to GND. Typical values
are 10kΩ and 2.2nF.
SS (Pin 12/Pin 13): Soft-Start. Place a soft-start capacitor
here. Leave fl oating if not in use.
GND (Pins 13, 14/Pins 8, 14, 15, 16): Ground. Tie directly
to local ground plane.
Exposed Pad (Pin 15/Pin 17): Power Ground. Must be
connected to electrical PCB ground.
(DFN/TSSOP)
