Standard Application Circuit

The standard application circuit (Figure 1) generates a

2.5V rail for general-purpose use in a notebook computer.

See Table 1 for component selections. Table 2 lists com-

ponent manufacturers.

High-Speed Step-Down Controller with

Accurate Current Limit for Notebook Computers

_______________________________________________________________________________________

9

PIN

QSOP

QFN

NAME

FUNCTION

14

11

Analog Supply Input. Connect to the system supply voltage, 4.5V to 5.5V, with a series 20

Ω resistor.

Bypass to GND with a 1µF (min) ceramic capacitor.

15

12

TON

On-Time Selection-Control Input. This four-level logic input sets the nominal DH on-time. Connect to

16

13

V+

Battery Voltage Sense Connection. Connect to input power source. V+ is used only to set the PWM

one-shot timing.

17

14

SKIP

enable pulse-skipping operation.

18

15

BST

Boost Flying-Capacitor Connection. Connect to an external capacitor and diode according to the

Standard Application Circuit (Figure 1). See the MOSFET Gate Drivers (DH, DL) section.

19

16

LX

External Inductor Connection. Connect LX to the switched side of the inductor. LX serves as the

lower supply rail for the DH high-side gate driver.

20

17

DH

High-Side Gate-Driver Output. Swings from LX to BST.

Pin Description (continued)

Table 1. Component Selection for

Standard Applications

COMPONENT

2.5V AT 4A

C1 Input Capacitor

10

µF, 25V

Taiyo Yuden TMK432BJ106KM or

TDK C4532X5R1E106M

C2 Output Capacitor

330

µF, 6V

Kemet T510X477108M006AS or

Sanyo 6TPB330M

D1 Schottky

Nihon EP10QY03

L1 Inductor

4.7

µH

Coilcraft DO33116P-682 or

Sumida CDRH124-4R7MC

Q1 High-Side MOSFET

Fairchild Semiconductor

1/2 FDS6982A

Q2 Low-Side MOSFET

Fairchild Semiconductor

1/2 FDS6982A

0.015

Ω ±1%, 0.5W resistor

IRC LR2010-01-R015F or

Dale WSL-2010-R015F

Table 2. Component Suppliers

*Distributor

SUPPLIER

USA PHONE

FACTORY FAX

Coilcraft

847-639-6400

1-847-639-1469

Dale-Vishay

203-452-5664

1-203-452-5670

Fairchild

408-822-2181

1-408-721-1635

IRC

800-752-8708

1-828-264-7204

Kemet

408-986-0424

1-408-986-1442

NIEC (Nihon)

805-867-2555*

81-3-3494-7414

Sanyo

619-661-6835

81-7-2070-1174

Sumida

847-956-0666

81-3-3607-5144

Taiyo Yuden

408-573-4150

1-408-573-4159

TDK

847-390-4461

1-847-390-4405