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LT1933

1933fe

PIN FUNCTIONS

BOOST (Pin 1): The BOOST pin is used to provide a drive

voltage, higher than the input voltage, to the internal bipolar

NPN power switch.

GND (Pin 2/Pin 5 and Exposed Pad, Pin 7): Tie the

GND pin to a local ground plane below the LT1933 and

the circuit components. Return the feedback divider to

this pin.

FB (Pin 3/Pin 6): The LT1933 regulates its feedback pin to

1.245V. Connect the feedback resistor divider tap to this

pin. Set the output voltage according to VOUT = 1.245V

(1 + R1/R2). A good value for R2 is 10k.

SHDN (Pin 4): The SHDN pin is used to put the LT1933 in

shutdown mode. Tie to ground to shut down the LT1933.

Tie to 2.3V or more for normal operation. If the shutdown

feature is not used, tie this pin to the VIN pin. SHDN also

provides a soft-start function; see the Applications Infor-

mation section.

VIN (Pin 5/Pin 2): The VIN pin supplies current to the

LT1933’s internal regulator and to the internal power

switch. This pin must be locally bypassed.

SW (Pin 6): The SW pin is the output of the internal power

switch. Connect this pin to the inductor, catch diode and

boost capacitor.

(SOT-23/DFN)

BLOCK DIAGRAM

DRIVER

OSC

SLOPE

COMP

FREQUENCY

FOLDBACK

INT REG

AND

UVLO

1.245V

1933 BD

BOOST

VOUT

VIN

ON OFF

GND

SHDN

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