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              1. "
                L4990
                L4990A
                PRIMARYCONTROLLER
                CURRENT-MODECONTROLPWM
                SWITCHINGFREQUENCYUPTO1MHz
                LOWSTART-UPCURRENT<0.45mA
                HIGH-CURRENTOUTPUTDRIVESUITABLE
                FORPOWERMOSFET(1A)
                FULLYLATCHEDPWMLOGICWITHDOU-
                BLEPULSESUPPRESSION
                PROGRAMMABLEDUTYCYCLE
                100%AND50%MAXIMUMDUTYCYCLE
                LIMIT
                PROGRAMMABLESOFTSTART
                PRIMARYOVERCURRENTFAULTDETEC-
                TIONWITHRE-STARTDELAY
                PWMUVLOWITHHYSTERESIS
                IN/OUTSYNCHRONIZATION
                DISABLELATCHED
                INTERNAL100nsLEADINGEDGEBLANK-
                INGOFCURRENTSENSE
                PACKAGE:DIP16ANDSO16W
                DESCRIPTION
                ThisprimarycontrollerI.C.,developedinBCD60II
                technology,hasbeendesignedtoimplementoff
                lineorDC-DCpowersupplyapplicationsusinga
                fixedfrequencycurrentmodecontrol.
                BasedonastandardcurrentmodePWMcontrol-
                lerthisdeviceincludessomefeaturesaspro-
                grammablesoftstart,IN/OUTsynchronization,
                disable(tobeusedforovervoltageprotection
                andforpowermanagement),precisemaximum
                DutyCycleControl,100ns(typ)leadingedge
                blankingoncurrentsense,pulsebypulsecurrent
                limitandovercurrentprotectionwithsoftstartin-
                tervention.
                July1999
                .
                +
                -
                +
                -
                TIMING
                2
                3
                +
                -
                14
                T
                Vref
                CLK
                2.5V
                +
                -
                1.2V
                13
                BLANKING
                PWM
                FAULT
                SOFT-START
                R
                SQ
                25V
                16V/10V
                VREFOK
                DIS
                +
                -
                E/A
                1VR
                2R
                DIS
                2.5V
                7
                6
                5
                11
                10
                9
                4
                8
                15
                1
                13V
                PWMUVLO
                12
                SGNDCOMP
                SS
                ISEN
                DIS
                DC
                RCT
                SYNCDC-LIMV
                CC
                VREF
                D98IN1002
                VFB
                PGND
                OUT
                V
                C
                OVERCURRENT
                BLOCKDIAGRAM
                ORDERINGNUMBERS:L4990/L4990A(DIP16)
                L4990D/L4990AD(SO16W)
                MULTIPOWERBCDTECHNOLOGY
                DIP16SO16W
                1/24
                9uu