LM34910

4

ON TIMER

280 ns

OFF TIMER

LEVEL

SHIFT

THERMAL

SHUTDOWN

7V SERIES

REGULATOR

UVLO

8V-36V

Input

C1

C5

10

SD

8

7

SS

6 FB

5

RTN

LOGIC

REGULATION

COMPARATOR

OVER-VOLTAGE

COMPARATOR

+

-

+

-

+

-

D1

SW 1

BST 2

COMPLETE

START

START

COMPLETE

C3

C4

R1

R2

R3

C2

CURRENT LIMIT

COMPARATOR

50 m:

2.875V

2.5V

11.5 PA

GATE DRIVE

UVLO

L1

+

-

+

-

0.7V

DRIVER

DRIVER

62.5 mV

C6

LM34910

SNVS297B – OCTOBER 2004 – REVISED MARCH 2013

www.ti.com

Typical Application Circuit and Block Diagram

PIN DESCRIPTIONS

PIN

NAME

DESCRIPTION

APPLICATION INFORMATION

Internally connected to the buck switch source. Connect to

1

SW

Switching Node

the external inductor, diode, and boost capacitor.

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

2

BST

Boost pin for boot-strap capacitor

internal diode charges the capacitor during the off-time.

Internally the current sense resistor connects from this pin to

3

Current sense input

wheeling diode. Current limit is set at 1.25A.

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

4

Sense Ground

resistor.

Ground for all internal circuitry other than the current limit

5

RTN

Circuit Ground

detection.

Internally connected to the regulation and over-voltage

6

FB

Feedback

comparators. The regulation level is 2.5V.

An internal 11.5 µA current source charges an external

7

SS

Softstart

capacitor to 2.5V to provide the softstart function.

8

On-time Control and Shutdown

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

Nominally regulated to 7.0V. An external voltage (8V-14V)

9

Output from the start-up regulator

can be connected to this pin to reduce internal dissipation.

10

Input supply voltage

Nominal input range is 8.0V to 36V.

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

2

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