MAX798 查看數據表（PDF） - Maxim Integrated

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MAX798

High-Accuracy Step-Down Controller with Synchronous Rectifier for CPU Power

Maxim Integrated 

High-Accuracy Step-Down Controller

with Synchronous Rectifier for CPU Power

VIN, 4.5V TO 30V

R3

2.2µF

10Ω

4.7µF

0.33µF

ON

OFF

V+

REF

SHDN

SKIP VL

BST

DH

LX

MAX798

DL

0.1µF

C3

47pF

0.01µF

SS

SYNC

PGND

R4

1M

CSH

CSL

FB

GND

C1

C2

Q1

L1

12µH

Q2

15mΩ

VOUT, +2.5V @ 4.2A

C4

C5

470pF

R1

R2

Q1, Q2 = SILICONIX Si4410DY or IRF7413

C1, C2 = 10µF/30V SANYO OS-CON (30SA10)

C4 = 470µF/4V SPRAGUE 594D SERIES (594D477X0004R2T)

L1 = SUMIDA CDRH127 120

R1 = 6.49kΩ, 1%

R2 = 11.5kΩ, 1%

f = 150kHz

Figure 1. Standard Application Circuit

_______________Detailed Description

The MAX798 is a BiCMOS, switch-mode power-supply

controller designed primarily for buck-topology regula-

tors in battery-powered applications where high accu-

racy, high efficiency, and low quiescent supply current

are critical. The MAX798 also works well in other

topologies such as boost, inverting, and CUK due to

the flexibility of its floating high-speed gate driver.

Light-load efficiency is enhanced by automatic idle-

mode operation—a variable-frequency pulse-skipping

mode that reduces losses due to MOSFET gate charge.

The step-down power-switching circuit consists of two

N-channel MOSFETs, a rectifier, and an LC output filter.

The output voltage is the average of the AC voltage at

the switching node, which is adjusted and regulated by

changing the duty cycle of the MOSFET switches. The

gate-drive signal to the N -channel high-side MOSFET

must exceed the battery voltage and is provided by a

flying capacitor boost circuit that uses a 100nF capaci-

tor connected between BST and LX.

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