MAX1624-MAX1625 查看數據表（PDF） - Maxim Integrated

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MAX1624-MAX1625

High-Speed Step-Down Controllers with Synchronous Rectification for CPU Power

Maxim Integrated 

High-Speed Step-Down Controllers with

Synchronous Rectification for CPU Power

REF

AGND

VCC

REF

REF1

REF2

SLOPE

COMPENSATION

FREQ

OSCILLATOR

CC1

CC2

REF

40k

10k

REF

REF2

REF1

WINDOW

RESET

Q

CONTROL AND

DRIVE LOGIC

Q

SET

MAX1625

N

CSL

CSH

BST

DH

LX

VDD

DL

PGND

FB

Figure 4. MAX1625 Simplified Block Diagram

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. Slope compensa-

tion is necessary to stabilize current-mode feedback

controllers with a duty cycle greater than 50%. Maximum

duty cycle is greater than 85% (see Typical Operating

Characteristics).

PWM Controller Block and Integrator

The heart of the current-mode PWM controller is a

multi-input open-loop comparator that sums three sig-

nals: the buffered feedback signal, the current-sense

PWROK

signal, and the slope-compensation ramp. This direct-

summing configuration approaches ideal cycle-by-

cycle control over the output voltage. The output

voltage error signal is generated by an error amplifier

that compares the amplified feedback voltage to an

internal reference.

Each pulse from the oscillator sets the main PWM latch

that turns on the high-side switch for a period deter-

mined by the duty factor (approximately VOUT / VIN).

The current-mode feedback system regulates the peak

inductor current as a function of the output voltage

14 ______________________________________________________________________________________

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