LM34919 datasheet(3/18 Pages) NSC

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Pin Descriptions

Pin Number

Name

Description

Application Information

RON/SD

On-time control and shutdown

An external resistor from VIN to this pin sets the buck switch

on-time. Grounding this pin shuts down the regulator.

RTN

Circuit Ground

Ground for all internal circuitry other than the current limit

detection.

Feedback input from the regulated

output

Internally connected to the regulation and over-voltage

comparators. The regulation level is 2.5V.

SGND

Sense Ground

Re-circulating current flows into this pin to the current sense

resistor.

Softstart

An internal current source charges an external capacitor to

2.5V, providing the softstart function.

ISEN

Current sense

The re-circulating current flows through the internal sense

resistor, and out of this pin to the free-wheeling diode.

Current limit is nominally set at 0.64A.

VCC

Output from the startup regulator

Nominally regulates at 7.0V. An external voltage (7V-14V)

can be applied to this pin to reduce internal dissipation. An

internal diode connects VCC to VIN.

VIN

Input supply voltage

Nominal input range is 8.0V to 40V.

Switching Node

Internally connected to the buck switch source. Connect to

the inductor, free-wheeling diode, and bootstrap capacitor.

BST

Boost pin for bootstrap capacitor

Connect a 0.022 µF capacitor from SW to this pin. The

capacitor is charged from V

CC via an internal diode during

each off-time.

LM34919 Datasheet(PDF) 3 Page - National Semiconductor (TI)

LM34919 Datasheet(HTML) 3 Page - National Semiconductor (TI)

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