SC420A 查看數據表（PDF） - Semtech Corporation

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SC420A

High Speed, Combi-Sense™, Synchronous Power MOSFET Driver for Mobile Applications

Semtech Corporation 

POWER MANAGEMENT

Applications Information (Cont.)

Start-up Sequencing

Proper sequencing of the Combi-SenseTM controller and

SC420A driver during both start-up and shut-down is very

important. In general, the design must ensure that the

driver powers up (during start-up) before the controller does,

and that the driver powers down last during shut-down.

This ensures that the driver will never issue gate drive

pulses that are not well-controlled.

In general it is recommended that the Vcc’s for the Combi-

Sense Controller and SC420A be connected to the same

(5V) supply. If the EN controls are not used (tied high)

then the UVLO settings for the controller and driver will

guarantee the proper sequencing (the SC420A maximum

UVLO value is guaranteed to be lower than the Combi-

SenseTM Controller minimum UVLO value).

For absolute guarantee of proper sequencing it is recom-

mended that the EN controls be used as shown in the

following block diagram. With this arrangement the de-

layed PWRGD signal from the VccVID regulator is used to

enable both ICs. The Soft-Start time established for the

controller ensures it will come up well after the SC420A.

During power-down de-assertion of VID_PWRGD will en-

sure simultaneous disabling of the Combi-SenseTM Control-

ler and SC420A.

SC420A

Manufacturing Guidlines

Detailed information on manufacturing and rework

of PCBs using the MLP package can be found in the

MLP application note “Comprehensive User’s Guide

- Micro Lead Frame Package”. Please contact your

local Semtech representative to obtain a copy of this

application note.

V5

SC1403

SYS_PWRGD

V3

VR_ON

VccVID Regulator

VID_PWRGD

Combi-

SenseTM

Controller

EN

Vcc-CORE

CO

SC420A

EN

VccPWRGD

© 2004 Semtech Corp.

10

United States Patent No. 6,441,597

www.semtech.com

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