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Datasheet

Datasheet

BM2PXX4 Series

TSZ02201-0F2F0A200070-1-2

24. Sep.2015.Rev.008

© 2012 ROHM Co., Ltd. All rights reserved.

www.rohm.com

TSZ22111・15・001

(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.

Vout

Switing

VH

VCC(1pin)

FB(8pin)

Soft

Start

64ms

Iout

Normal Load

Light LOAD

Within

32ms

VCC=8.2V

Over Load

Internal REF

Pull Up

Burst mode

AB C

D

EF

GH

I

Switching

stop

VCC=13.5V

FB OLP ON

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).

Switching function starts when other protection functions are judged as normal. Until the secondary output voltage

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 (7.7Vtyp) or below, restart is executed.

I: The IC’s circuit current is reduced and the VCC pin value rises. (Same as B)