UC3844D Datasheet | STMicroelectronics

DESCRIPTION The UC3842/3/4/5family of control ICs provides the necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal externalparts count.Internallyimplementedcircuits include undervoltagelockout featuring start-up current less than 1 m A, a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM paratorwhich also providescurrentlimit control,and a totem pole output stage designed to source or sink high peak current. The output stage, suitable for driving N-Channel MOSFETs, is low in theoff-state. Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle ranges. The UC3842 and UC3844 have UVLO thresholds of 16V (on) and 10V (off), ideally suited off-line applications The corresponding thresholds for the UC3843 and UC3845 are 8.5 V and 7.9 V. The UC3842 and UC3843 can operate to duty cycles approaching 100%. A range of the zero to < 50 % is obtained by the UC3844 and UC3845 by the additionof an internal toggle flip flop which blanks the output off every other clock cycle. BLOCK DIAGRAM (toggle flip flop used only in U3844 and UC3845) October 1998 1/11 UC2842/3/4/5-UC3842/3/4/5 ABSOLUTE MAXIMUM RATINGS Symbol Vi Vi IO EO Parameter Supply Voltage (low impedance source) Supply Voltage (Ii < 30m A) Output Current Output Energy (capacitive load) Analog Inputs (pins 2, 3) Error Amplifier Output Sink Current Ptot Ptot Tstg TL Power Dissipation at Tamb ≤ 50 °C (minidip, DIP-14) Power Dissipation at Tamb ≤ 25 °C (SO14) Storage Temperature Range Lead Temperature (soldering 10s) Value 30 Self Limiting ±1 5 - 0.3 to 6.3 10 1 725 - 65 to 150 300 A µJ V m A W m W °C °C Unit V - All voltages are with respect to pin 5, all currents are positive into the specified terminal. PIN CONNECTIONS (top views) SO14 Minidip ORDERING NUMBERS T ype UC2842 UC3843 UC2844 UC2845 UC3842 UC3843 UC3844 UC3845 Min idip UC2842N UC2843N UC2844N...