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BM2PXX2F
(2) Start sequences
(Soft start operation, light load operation, and auto recovery operation during overload protection)
Start sequences are shown in Figure 7. See the sections below for detailed descriptions.
VH
VCC=13.5V
VCC(1pin)
VCC=8.2V
Within
32ms
FB OLP ON
64ms
Internal REF
Pull Up
FB(8pin)
Vout
Iout
Over Load
Normal Load
Light LOAD
Burst mode
Switching
stop
Switing
Soft
Start
G H
I
C
E
F
A
B
D
Figure 7. Start sequences Timing Chart
A: Input voltage VH is applied
B: This IC starts operation when VCC pin voltage rises and VCC > VUVLO1 (13.5 V typ).Becomes constant level, VCC
voltage drops because of the VCC consumption current. VCC recharge function start if VCC voltage<VCHG1（8.7V
typ）
C: With the soft start function, over current limit value is restricted to prevent any excessive rise in voltage or current.
D: When the switching operation starts, VOUT rises.The output voltage become to stable state, VCC voltage also
become to stable state through auxiliary winding.Please set the rated voltage within the TFOLP1b period (32ms typ)
from VCC voltage > VUVLO1.
E: During a light load, if it reaches FB voltage < VBST (= 0.4Vtyp), the IC starts burst operation to keep power
consumption low. During burst operation, it becomes low-power consumption mode.
F: When the FB Voltage＞VFOLP1A（=2.8V typ）, it becomes a overload operation.
G: When FB pin voltage keeps VFOLP1A (= 2.8V typ) at or above T FOLP (64ms typ), the overload protection function is
triggered and switching stops 64mS later. If the FB pin voltage becomes FB<VFOLP1B even once, the IC’s FB OLP
timer is reset.
H: If the VCC voltage drops to VCC < VUVLO2 (8.2Vtyp) or below, restart is executed.
I: The IC’s circuit current is reduced and the VCC pin value rises. (Same as B)
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TSZ02201-0F2F0A200040-1-2
7. Mar.2017.Rev.007
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