9014 查看數據表（PDF） - Fairchild Semiconductor

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9014

Fairchild QFET for Synchronous Rectification DC to DC Converters

Fairchild Semiconductor 

3. Synchronous Rectification DC to DC Converter

Recent increases in computer microprocessor processing speed have demanded lower oper-

ating voltages. A broad range of input voltages and currents are required by Intel microproces-

sors with processing speeds that range from 233-1000MHz. Tables 3-1 and 2 list voltage and

current specifications recommended by Intel Corp for the Celeron™ and Pentium® III proces-

sors. (Refer to Intel VRM 8.4 DC-DC Converter Design Guidelines)

Table 3-1. Pentium® III processor (>2.0V) Voltage and Current Specifications

Symbol

VccCORE

IccCORE

IccSGNTCORE

IccDSLPCORE

dIccCORE/dt

Parameter

VCC for processor core

VccCORE static tolerance at

processor connector pins on

system board

VccCORE transient tolerance

at processor connector pins

on system board

Current for VccCORE

ICC for Stop-Gain VccCORE

ICC for Deep-Sleep VccCORE

ICC slew rate

Processor core

frequency [MHz]

<600

600 / 600B

600 / 600B

550

533B

500

450

Min. Typ. Max.

2.00

2.05

-0.070

0.070

-0.140

0.140

17.8

17.0

16.7

16.1

14.5

1.68

0.50

20

Unit

V

V

V

A

A

A

A/µs

Table 3-2. Pentium® III processor (<1.7V) Voltage and Current Specifications

Symbol

Parameter

VccCORE

VCC for processor core

VccCORE static tolerance at

processor connector pins on

system board

VccCORE transient tolerance

at processor connector pins

on system board

IccCORE

Current for VccCORE

IccSGNTCORE

IccDSLPCORE

dIccCORE/dt

ICC for Stop-Gain VccCORE

ICC for Deep-Sleep VccCORE

ICC slew rate

Processor core

frequency [MHz]

All SECC2

All PC-GPA

All SECC2

All FC-PGA

All SECC2

All FC-PGA

700-733

600-667

500-550

Min. Typ. Max.

1.65

1.60

-0.080

0.040

-0.080

0.040

-0.080

0.050

-0.130

0.080

14.6

13.3

11.0

2.5

2.2

20

Unit

V

V

V

A

A

A

A/µs

The DC-DC converter responsible for supplying only the microprocessor input voltage and

current recommended in Tables 3-1 and 2, used in the computer motherboard, is required to

output high quality DC voltage almost free of ripples. Because of system characteristics, a

step-down DC-DC converter that employs feedback control through the PWM controller is

generally used. Figure 3-1 shows the basic circuit of a step-down (Buck topology) DC-DC con-

3

Rev. B, July 2000

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