LM5574-Q1

SNOSB22C – OCTOBER 2008 – REVISED OCTOBER 2014

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Pin Functions (continued)

PIN

I/O

DESCRIPTION

APPLICATION INFORMATION

NO.

NAME

12

PGND

Ground

Power ground

Low side reference for the PRE switch and the IS

sense resistor.

13

IS

I

Current sense

Current measurement connection for the re-

circulating diode. An internal sense resistor and a

sample/hold circuit sense the diode current near the

conclusion of the off-time. This current measurement

provides the DC level of the emulated current ramp.

14

SW

O

Switching node

The source terminal of the internal buck switch. The

SW pin should be connected to the external Schottky

diode and to the buck inductor.

15

PRE

O

Pre-charge assist for the bootstrap capacitor

This open drain output can be connected to SW pin

to aid charging the bootstrap capacitor during very

light load conditions or in applications where the

output may be pre-charged before the LM5574-Q1 is

enabled. An internal pre-charge MOSFET is turned

on for 250 ns each cycle just prior to the on-time

interval of the buck switch.

16

BST

I

Boost input for bootstrap capacitor

An external capacitor is required between the BST

and the SW pins. A 0.022-µF ceramic capacitor is

via an internal diode during the off-time of the buck

switch.

6 Specifications

6.1 Absolute Maximum Ratings

(1) (2)

MIN

MAX

UNIT

76

V

BST to GND

90

V

PRE to GND

76

V

SW to GND (Steady State)

–1.5

V

76

V

14

V

BST to SW

14

V

OUT to GND

SYNC, SS, FB, RAMP to GND

7

V

(1)

Absolute Maximum Ratings are limits beyond which damage to the device may occur. Recommended Operating Conditions are

conditions under which operation of the device is intended to be functional. For ensured specifications and test conditions, see the

Electrical Characteristics.

(2)

If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and

specifications.

6.2 Handling Ratings

MIN

MAX

UNIT

Storage temperature range

–65

150

°C

Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all

2

Electrostatic discharge

kV

(1)

JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

6.3 Recommended Operating Conditions

MIN

MAX

UNIT

6

75

V

Operation Junction Temperature

–40

150

°C

4

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