44608 데이터 시트보기 (PDF) - ON Semiconductor

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44608

Few External Components Reliable and Flexible SMPS Controller

ON Semiconductor 

MC44608

EQUATION 7

dBM +

ȧȡȢ 1 )

IccS) IG

Istup

1

ǒ ǒ kSńStup ) kSńL

ǓǓ Istup

IccL) Ipin3

ȧȣȤ

EQUATION 8

dBM +

ȡ

ǒ Ǔ ȧȧȥ 1 )

k1

)

IG

Istup

Ȣ

1

ȡ

ȧȧȧkSńStup ) (kSńL

Ȣ

ȣȣ

ǒ Ǔ k2)

1

Ipin3

Istup

)ȧȧȧȧȧȦ

ȤȤ

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 stand−by mode.

EQUATION 9

Ipkstby +

Vcs–th * (Rcs

RS

Ics)

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

Ipkstby + Vcs–th

ǒ Ǔ 1 * Rcs

Ics

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 (dtcs) and the Power Switch reaction time (dtps):

EQUATION 12

ƪ Ipkstby + Vcs–th

ƫ 1 * (Rcs Ycs–stby )

RS

) Vin

(dtcs ) dtps)

Lp

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10

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