1

2

3

4

5

10

9

8

7

6

VIN

VCC

RT

FB

UVO

SW

BST

N/C

RTN

UV

LM34923

SNVS695 – MARCH 2011

www.ti.com

Connection Diagram

Figure 1. Top View

10–Lead MSOP

Pin Functions

Pin Descriptions

Pin

Name

Description

Application Information

1

SW

Switching Node

Power switching node. Connect to the output inductor, re-circulating diode or

synchronous FET, and bootstrap capacitor.

2

BST

Boost Pin

An external capacitor is required between the BST and the SW pins (0.01uF or

greater ceramic). The BST pin capacitor is charged from Vcc through an internal

diode when SW is low.

3

N/C

Do not connect

4

RTN

Ground pin

Ground for the entire circuit.

5

UV

Input pin for the under voltage

A resistor divider from VIN, or some other system voltage, programs the under-

indicator

voltage detection threshold. An internal current sink is enabled when UV is

below 2.5V to provide hysteresis.

6

UVO

Under voltage status indicator

This open drain output is high when the UV pin voltage is below 2.5V, or when

7

FB

Feedback Input from Regulated

This pin is connected to the inverting input of the internal regulation comparator.

Output

The regulation level is 2.5V.

8

RT/SD

On-time set pin and shutdown input

A resistor between this pin and Vin sets the switch on-time as a function of Vin,

and the frequency. The minimum recommended on-time is 200 ns at max input

voltage. Taking this pin to ground shuts off the regulator.

9

VCC

Output from the internal high voltage

The internal regulator provides bias supply for the Buck switch gate driver and

series pass regulator. Regulated at

other internal circuitry. A 1uF ceramic capacitor to ground is required. The

7.5V.

regulator is current limited to

≈30 mA.

10

VIN

Input Voltage

The operating input range is 6V to 75V

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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