Datasheet

LT3502/LT3502A
7
3502fd
pin Functions
V
IN
(Pin 1/Pin 10): The V
IN
pin supplies current to the
LT3502/LT3502A’s internal regulator and to the internal
power switch. This pin must be locally bypassed.
BD (Pin 2/Pin 8): The BD pin is used to provide current
to the internal boost Schottky diode.
FB (Pin 3/Pin 7): The LT3502/LT3502A regulate their
feedback pin to 0.8V. Connect the feedback resistor di
-
vider tap to this pin. Set the output voltage according to
V
OUT
= 0.8 (1 + R1/R2). A good value for R2 is 10k.
SHDN (Pin 4/Pin 6): The SHDN pin is used to put the
LT3502 in shutdown mode. Tie to ground to shut down
the LT3502/LT3502A. Tie to 2V or more for normal
operation. If the shutdown feature is not used, tie this pin
to the
V
IN
pin. The SHDN pin also provides soft-start and
frequency foldback. To use the soft-start feature, connect
R3 and C4 to the SHDN pin. SHDN Pin voltage should
not be higher than V
IN
.
GND (Pin 5/Pin 5): Ground Pin.
DA (Pin 6/Pin 4): Connect the catch diode (D1) anode to
this pin. This pin is used to provide frequency foldback
in extreme situations.
BOOST (Pin 7/Pin 2): The BOOST pin is used to provide a
drive voltage, higher than the input voltage, to the internal
bipolar NPN power switch. Connect a boost capacitor from
this pin to SW Pin.
SW (Pin 8/Pin 1): The SW pin is the output of the internal
power switch. Connect this pin to the inductor, catch diode
and boost capacitor.
(DFN/MS)