3513 datasheet(9/20 Pages) LINER

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LT3513

3513fa

SENSE+ (Pin 31) Positive Current Sense Input. This pin

(along with the SENSE– pin) is used to sense the inductor

current for the buck switching regulator.

FB1 (Pin 32): Feedback Pin. Tie the resistor divider tap

to this pin and set VLOGIC according to VLOGIC = 1.23V •

(1 + R1/R2). Reference designators refer to Figure 2.

SW1 (Pins 34, 35): Switch Node. The SW1 pins are the

emitter of the internal NPN bipolar power transistor for

switching regulator 1. These points must be tied together

for proper operation. Connect these pins to the inductor,

catch diode and boost capacitor.

VIN (Pins 36, 37): Input Voltage. This pin supplies current

to the internal circuitry of the LT3513. This pin must be

locally bypassed with a capacitor.

UVLO (Pin 38): Undervoltage Lockout. A resistor divider

connected to VIN is tied to this pin to program the minimum

input voltage at which the LT3513 will operate. This pin is

compared to the internal 1.25V reference. When UVLO is

less than 1.25V, the switching regulators are not allowed

to operate (the RUN/SS pins are still used to turn on each

switching regulator). When this pin falls below 1.25V,

3.9μA will be pulled from the pin to provide programmable

hysteresis for UVLO.

Exposed Pad (Pin 39): Ground. The Exposed Pad of the

package provides both electrical contact to ground and

good thermal contact to the printed circuit board. The

Exposed Pad must be soldered to the circuit board for

proper operation.

PIN FUNCTIONS

3513 Datasheet(PDF) 9 Page - Linear Technology