描述 Description

The UC284xB family of control ICs provides the necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. Internally implemented circuits include a trimmed oscillator for precise DUTY CYCLE CONTROL under voltage lockout featuring start-up current less than 0.5mA, a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM comparator which also provides current limit 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 the off-state.

Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle ranges. The UC2842B and UC2844B have UVLO thresholds of 16V (on) and 10V (off), ideally suited off-line applications The corresponding thresholds for the UC2843B and UC2845B are 8.5V and 7.9V. The UC2842B and UC2843B can operate to duty cycles approaching 100%. A range of the zero to < 50 % is obtained by the UC2844B and UC2845B by the addition of an internal toggle flip flop which blanks the output off every other clock cycle.

特性 Features

? LOW START-UP AND OPERATING CURRENT
? UNDERVOLTAGE LOCKOUT WITH HYSTERESIS
? INTERNALLY TRIMMED REFERENCE WITH UNDERVOLTAGE LOCKOUT
? CURRENT LIMITING
? TRIMMED OSCILLATOR FOR PRECISE FREQUENCY CONTROL
? CURRENT MODE OPERATION TO 500kHz
? OSCILLATOR FREQUENCY GUARANTEED AT 250kHz
? LATCHING PWM FOR CYCLE-BY-CYCLE
? HIGH CURRENT TOTEM POLE OUTPUT
? AUTOMATIC FEED FORWARD COMPENSATION

簡介

UC3844B屬于集成電路（IC）的DC-DC開關(guān)控制器。由制造生產(chǎn)的UC3844BDC-DC 開關(guān)控制器PMIC（電源管理集成電路）DC 到 DC 開關(guān)式控制器是用于高效率電路的穩(wěn)壓 IC，其配置為生成高于（突升或步升）或低于（突降或步降）輸入電源的輸出電源電壓。其他拓?fù)浣Y(jié)構(gòu)可能包括：降壓-升壓、反激、正激、Cuk、SEPIC、全橋、半橋和推挽式。這些器件不同于需要最小電壓并“燒盡”多余電壓的線性穩(wěn)壓器。