Rainbow-electronics MAX1844 Manual de usuario descargar pdf (Pagina 9)

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.

MAX1844

High-Speed Step-Down Controller with

Accurate Current Limit for Notebook Computers

_______________________________________________________________________________________ 9

QSOP QFN

NAME

FUNCTION

14 11

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

GND, REF, V

, or leave TON unconnected to select the following nominal switching frequencies:

GND = 600kHz, REF = 450kHz, floating = 300kHz, and V

= 200kHz.

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

Pulse-Skipping Control Input. Connect to V

for low-noise, forced-PWM mode. Connect to GND to

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

10µF, 25V

Taiyo Yuden TMK432BJ106KM or

TDK C4532X5R1E106M

C2 Output Capacitor

330µF, 6V

Kemet T510X477108M006AS or

Sanyo 6TPB330M

D1 Schottky Nihon EP10QY03

L1 Inductor

4.7µH

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

SENSE

0.015Ω ±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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 22 23

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Rainbow-electronics MAX1844 Manual de usuario Pagina 9

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