BM2P034 datasheet(7/19 Pages) ROHM

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Datasheet

BM2PXX4 Series

TSZ02201-0F2F0A200070-1-2

28.NOV.2012.Rev.003

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

Switching

VCC(1pin)

FB(8pin)

Soft

Start

Within

32ms

Iout

Normal Load

Light LOAD

Within

32ms

VCC=8.2V

Over Load

Within

32ms

Internal REF

Pull Up

Burst mode

B C

Switching

stop

VCC=13.5V

Figure 7. Start sequences Timing Chart

A : Input voltage VH is applied

B : This IC starts operating VCC pin voltage rises when VCC > V

UVLO1 (13.5 V typ).

Switching function starts when other protection functions are judged as normal.

Between the secondary output voltage become constant level, because the VCC pin consumption current causes the VCC

value to drop, IC should set to start switching until VCC<V

UVLO2 (8.2V typ).

C : With the soft start function, overcurrent limit value is restricted to prevent any excessive rise in voltage or current.

D : When the switching operation starts, VOUT rises.

Once the output voltage starts, set the rated voltage within the T

FOLP period (32ms typ).

E : When there is a light load it reaches FB voltage < VBST (= 0.4Vtyp, burst operation is used to keep power consumption

down.

During burst operation, it becomes low-power consumption mode.

F : When the FB Voltage＞V

FOLP1A（=2.8V.typ）, it becomes a overload

G: When FB pin voltage keeps V

FOLP1A (= 2.8V typ) at or above T FOLP (32ms typ), the overload protection function is triggered

and switching stops. During the TFOLP period (32ms typ) if the FB pin voltage becomes FB<VFOLP1B even once, the IC’s

internal timer is reset.

H : If the VCC voltage drops to VCC < V

UVLO2 (7.7Vtyp) or below, restart is executed.

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

J : Same as F

K : Same as G

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