LT3493 Просмотр технического описания (PDF) - Linear Technology

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LT3493

1.2A, 750kHz Step-Down Switching Regulator in 2mm × 3mm DFN

Linear Technology 

LT3493

PIN FUNCTIONS

FB (Pin 1): The LT3493 regulates its feedback pin to

780mV. Connect the feedback resistor divider tap to this

pin. Set the output voltage according to VOUT = 0.78V •

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

GND (Pin 2): Tie the GND pin to a local ground plane

below the LT3493 and the circuit components. Return the

feedback divider to this pin.

BOOST (Pin 3): The BOOST pin is used to provide a drive

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

NPN power switch.

SW (Pin 4): The SW pin is the output of the internal power

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

boost capacitor.

VIN (Pin 5): The VIN pin supplies current to the LT3493’s

internal regulator and to the internal power switch. This

pin must be locally bypassed.

SHDN (Pin 6): The SHDN pin is used to put the LT3493 in

shutdown mode. Tie to ground to shut down the LT3493.

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.

Exposed Pad (Pin 7): The Exposed Pad must be soldered

to the PCB and electrically connected to ground. Use a

large ground plane and thermal vias to optimize thermal

performance.

BLOCK DIAGRAM

VIN

5 VIN

C2

INT REG

AND

UVLO

ON OFF

R3

SHDN

6

C4

3

SLOPE

COMP

OSC

FREQUENCY

FOLDBACK

VC

RQ

SQ

gm

780mV

DRIVER

BOOST

3

Q1

SW

4

D2

C3

L1

D1 C1

VOUT

GND

2

FB

1

R2

R1

3493 BD

3493fb

6

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