LT3470
6
3470fd
SHDN (Pin 1/Pin 8): The SHDN pin is used to put the
LT3470 in shutdown mode. Tie to ground to shut down
the LT3470. Apply 2V or more for normal operation. If the
shutdown feature is not used, tie this pin to the V
IN
pin.
NC (Pin 2/Pin 7): This pin can be left floating or connected
to V
IN
.
V
IN
(Pin 3/Pin 6): The V
IN
pin supplies current to the
LT3470’s internal regulator and to the internal power
switch. This pin must be locally bypassed.
GND (Pin 4/Pin 5): Tie the GND pin to a local ground plane
below the LT3470 and the circuit components. Return the
feedback divider to this pin.
SW (Pin 5/Pin 4): The SW pin is the output of the internal
power switch. Connect this pin to the inductor, catch diode
and boost capacitor.
BOOST (Pin 6/Pin 3): The BOOST pin is used to provide
a drive voltage, which is higher than the input voltage, to
the internal bipolar NPN power switch.
BIAS (Pin 7
/Pin 2):
The BIAS pin connects to the internal
boost Schottky diode and to the internal regulator. Tie to
V
OUT
when V
OUT
> 2V or to V
IN
otherwise. When V
BIAS
>
3V the BIAS pin will supply current to the internal regulator.
FB (Pin 8
/Pin 1):
The LT3470 regulates its feedback pin
to 1.25V. Connect the feedback resistor divider tap to this
pin. Set the output voltage according to V
OUT
= 1.25V
(1 + R1/R2) or R1 = R2 (V
OUT
/1.25 – 1).
Exposed Pad (
DD, Pin 9):
Ground. Must be soldered to
PCB.
Boost Diode Forward Voltage
Minimum Input Voltage, V
OUT
= 3.3V
Minimum Input Voltage, V
OUT
= 5V
Typical perForMance characTerisTics
BOOST DIODE CURRENT (mA)
0
SCHOTTKY V
F
(V)
500
600
700
200
3470 G17
400
300
0
50
100
150
100
200
900
800
LOAD CURRENT (mA)
0
3.0
INPUT VOLTAGE (V)
3.5
4.0
4.5
5.0
5.5
6.0
50 100 150 200
3470 G18
T
A
= 25°C
V
IN
TO START
V
IN
TO RUN
LOAD CURRENT (mA)
0
INPUT VOLTAGE (V)
6
7
200
3470 G19
5
4
50
100
150
8
T
A
= 25°C
V
IN
TO START
V
IN
TO RUN
pin FuncTions
(ThinSOT/DD)
