LM3151, LM3152, LM3153

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SNVS562G – SEPTEMBER 2008 – REVISED MARCH 2011

PIN DESCRIPTIONS

Pin

Name

Description

Function

Supply Voltage for

Nominally regulated to 5.95V. Connect a 1 µF to 2.2 µF decoupling capacitor from this pin to

1

VCC

FET Drivers

ground.

Supply pin to the device. Nominal input range is 6V to 42V. See ordering information for Vin

2

VIN

Input Supply Voltage

limitations.

To enable the IC apply a logic high signal to this pin greater than 1.26V typical or leave

3

EN

Enable

floating. To disable the part, ground the EN pin.

Internally connected to the resistor divider network which sets the fixed output voltage. This

4

FB

Feedback

pin also senses the output voltage faults such a over-voltage and short circuit conditions.

Ground for all internal bias and reference circuitry. Should be connected to PGND at a single

5,9

SGND

Signal Ground

point.

An internal 7.7 µA current source charges an external capacitor to provide the soft-start

6

SS

Soft-Start

function.

Internally not electrically connected. These pins may be left unconnected or connected to

7,8

N/C

Not Connected

ground.

Switch pin of controller and high-gate driver lower supply rail. A boost capacitor is also

10

SW

Switch Node

connected between this pin and BST pin

Gate drive signal to the high-side NMOS switch. The high-side gate driver voltage is supplied

11

HG

High-Side Gate Drive

by the differential voltage between the BST pin and SW pin.

High-gate driver upper supply rail. Connect a 0.33 µF-0.47 µF capacitor from SW pin to this

Connection for

12

BST

pin. An internal diode charges the capacitor during the high-side switch off-time. Do not

Bootstrap Capacitor

connect to an external supply rail.

Gate drive signal to the low-side NMOS switch. The low-side gate driver voltage is supplied by

13

LG

Low-Side Gate Drive

VCC.

Synchronous rectifier MOSFET source connection. Tie to power ground plane. Should be tied

14

PGND

Power Ground

to SGND at a single point.

Exposed die attach pad should be connected directly to SGND. Also used to help dissipate

EP

EP

Exposed Pad

heat out of the IC.

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