LT3470 LINEAR [Linear Integrated Systems], LT3470 Datasheet - Page 6

• Manufacturer Part Number: LT3470
• Description: Micropower Buck Regulator with Integrated Boost and Catch Diodes
• Manufacturer: LINEAR [Linear Integrated Systems]

PI FU CTIO S
BLOCK DIAGRA
LT3470
SHDN (Pin 1): 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
NC (Pin 2): This pin can be left floating or connected to V
V
internal regulator and to the internal power switch. This
pin must be locally bypassed.
GND (Pin 4): Tie the GND pin to a local ground plane below
the LT3470 and the circuit components. Return the feed-
back divider to this pin.
SW (Pin 5): The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
6
IN
U
(Pin 3): The V
V
IN
U
C1
IN
3
2
1
U
pin supplies current to the LT3470’s
V
NC
SHDN
IN
W
ONE SHOT
500ns
1.25V
V
REF
R2
FB
8
R1
BURST MODE
IN
DETECT
R
S
pin.
g
m
ENABLE
Q′
Q
+
–
IN
.
BOOST (Pin 6): 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): The BIAS pin connects to the internal boost
Schottky diode and to the internal regulator. Tie to V
when V
BIAS pin will supply current to the internal regulator.
FB (Pin 8): 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
(1 + R1/R2) or R1 = R2 (V
–
+
OUT
> 2V or to V
GND
4
BOOST
IN
BIAS
SW
otherwise. When V
OUT
7
6
5
/1.25 – 1).
C3
L1
C2
3470 BD
BIAS
OUT
V
OUT
> 3V the
= 1.25V
OUT
3470f