IL44608 Datasheet, PDF (9/13 Pages) IK Semicon Co., Ltd – External Components Reliable and Flexible SMPS Controller

IL44608N
EQUATION 1
Start–up Phase Duration:
t _{START−UP}
=
C _Vcc
× (V_STUP − UOLO2)
I _STUP
where: I_stup is the start–up current flowing through V_CC pin
C_Vcc is the V_CC capacitor value
EQUATION 2
Switching Phase Duration:
t _switch
=
C _Vcc
× (V_STUP − UOLO1)
I _ccS + I _G
where: I_ccS is the no load circuit consumption in switching phase
I_G is the current consumed by the Power Switch
EQUATION 3
Latched–off Phase Duration:
t _{latched−off}
= ^{C Vcc}
× (UVLOP1 − UOLO2)
I _ccL + I _pin3
where: I_ccL is the latched off phase consumption
I_pin3 is the current drawn from pin3 adding a resistor
EQUATION 4
Burst Mode Duty Cycle:
t _SWITCH
d = _BM
t + t + t _start-up
switch
latched-off
EQUATION 5
C _Vcc × (V_STUP − UVLO1)
d _BM
=
C _Vcc
× (V_STUP
− UVLO2)
+
C _Vcc
I _ccS + I _G
× (V_STUP − UVLO1)
+
C _Vcc
× (UVLO1 − UVLO2)
I _STUP
I _ccS + I _G
I _ccL + I _Ipin3
EQUATION 6
d _BM
=
1
+


k
S/Stup
× ^{IccS + IG}
I _stup
1


+


k
S/L
×
I_ccS + I_G
I_ccL + I _pin3


where: k_S/Stup = (V_stup – UVLO2)/(V_stup – UVLO1)
k_S/L = (UVLO1 – UVLO2)/(V_stup – UVLO1)
EQUATION 7
d _BM
=

1 +

I_ccS + I_G
I _stup
1

×


k
S/Stup
+


k
S/L

×
I _stup
I_ccL + I _pin3



2011, February, Rev. 01