MC44608(2010) 데이터 시트보기 (PDF) - ON Semiconductor

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MC44608
(Rev.:2010)

Few External Components Reliable and Flexible SMPS Controll

ON Semiconductor 

MC44608

EQUATION 1

Startup Phase Duration:

tstart–up

=

CVcc

×

(Vstup −

Istup

UVLO2)

where: Istup is the startup current flowing through VCC pin

CVcc is the VCC capacitor value

EQUATION 2

Switching Phase Duration:

tswitch

=

CVcc

× (Vstup

IccS +

− UVLO1)

IG

where: IccS is the no load circuit consumption in switching phase

IG is the current consumed by the Power Switch

EQUATION 3

Latched--off Phase Duration:

tlatched−off

=

CVcc

× (UVLO1 − UVLO2)

IccL + Ipin3

where: IccL is the latched off phase consumption

Ipin3 is the current drawn from pin3 adding a resistor

EQUATION 4

Burst Mode Duty Cycle:

dBM

=

tstart−up

+

tswitch

tswitch +

tlatched−off

EQUATION 5

CVcc× (Vstup −UVLO1)

dBM

=

CVcc×(Vstup −

Istup

UVLO2)

+

IccS+ IG

CVcc× (Vstup −UVLO1)

IccS+ IG

+

CVcc× (UVLO1−UVLO2)

IccL+ Ipin3

EQUATION 6

    dBM =

1+

1

kS∕Stup

×

IccS+ IG

Istup

+

kS∕L

×

IccS+ IG

IccL+ Ipin3

where: kS/Stup = (Vstup -- UVLO2)/(Vstup -- UVLO1)

kS/L = (UVLO1 -- UVLO2)/(Vstup -- UVLO1)

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