MC44608(2010) Ver la hoja de datos (PDF) - ON Semiconductor

Número de pieza

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MC44608
(Rev.:2010)

Few External Components Reliable and Flexible SMPS Controll

ON Semiconductor 

MC44608

EQUATION 7

dBM =

1

⎪⎧⎩ ⎪⎧⎩  ⎪⎫⎭⎪⎫⎭ 1 +

IccS+ IG

Istup

×

kS∕Stup +

kS∕L

×

Istup

IccL+ Ipin3

EQUATION 8

    dBM =

⎪⎪⎨⎧⎩ 1 +

k1

+

IG

Istup

1

⎧

⎪⎪⎪⎩×

kS∕Stup + (kS∕L ×

k2+

1

Ipin3

Istup

)⎪⎪⎪⎫⎭⎪⎪⎬⎫⎭

where: k1 = Iccs/Istup

k2 = IccL/Istup

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

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

PULSED MODE CURRENT SENSE CLAMPING LEVEL

Equations 9, 10, 11 and 12 allow the calculation of the Rcs value for the desired maximum current peak value during the

SMPS standby mode.

EQUATION 9

Ipkstby =

Vcs–th − (Rcs × Ics)

RS

where: Vcs--th is the CS comparator threshold

Ics is the CS internal current source

RS is the sensing resistor

Rcs is the resistor connected between pin 2 and RS

EQUATION 10

  1 −

Rcs ×

Ics

Vcs–th

Ipkstby = Vcs–th ×

RS

EQUATION 11

Ipkstby

=

Vcs–th

×

1

−

(Rcs

× Ycs–stby

RS

)

where: Ycs--stby = Ics/Vcs--th

Taking into account the circuit propagation delay (δtcs) and the Power Switch reaction time (δtps):

EQUATION 12

  Ipkstby =

Vcs–th

×

1

−

(Rcs

× Ycs–stby

RS

)

+

Vin

×

(δtcs

Lp

+

δtps)

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