PH

VIN

15

14

13

GND

12

11

10

9

8

7

6

5

16

GND

VIN

PH

PH

1

2

3

4

SS/TR

PowerPAD

(17)

QFN16

RTE PACKAGE

(TOP VIEW)

TPS54478

www.ti.com

SLVSAS2

– JUNE 2011

ELECTRICAL CHARACTERISTICS (continued)

DESCRIPTION

CONDITIONS

MIN

TYP

MAX

UNIT

Output low

0.2

0.3

V

Minimum VIN for valid output

1.2

1.6

V

DEVICE INFORMATION

PIN CONFIGURATION

PIN FUNCTIONS

PIN

DESCRIPTION

NAME

NO.

AGND

5

Analog Ground should be electrically connected to GND close to the device.

BOOT

13

A bootstrap capacitor is required between BOOT and PH. If the voltage on this capacitor is below the minimum

required by the BOOT UVLO, the output is forced to switch off until the capacitor is refreshed.

COMP

7

Error amplifier output, and input to the output switch current comparator. Connect frequency compensation

components to this pin.

EN

15

Enable pin, internal pull-up current source. Pull below 1.21 V to disable. Float to enable. Can be used to set the

on/off threshold (adjust UVLO) with two additional resistors.

GND

3, 4

Power Ground. This pin should be electrically connected directly to the power pad under the IC.

PH

10, 11,

The source of the internal high side power MOSFET, and drain of the internal low side (synchronous) rectifier

12

MOSFET.

PowerPAD

17

GND pin should be connected to the exposed power pad for proper operation. This power pad should be

connected to any internal PCB ground plane using multiple vias for good thermal performance.

PWRGD

14

An open drain output; asserts low if output voltage is low due to thermal shutdown, overcurrent,

over/under-voltage or EN shut down.

RT/CLK

8

Resistor Timing or External Clock input pin.

SS/TR

9

Slow start and tracking. An external capacitor connected to this pin sets the output voltage rise time. The SS

provides higer charge current when SS is below 0.15V, resulting in two slopes of the SS voltage.

This pin can also be used for tracking.

VIN

1, 2, 16

Input supply voltage, 2.95 V to 6 V.

Copyright

© 2011, Texas Instruments Incorporated

5