UC1845A

电流模式PWM控制器 CURRENT MODE PWM CONTROLLER

DESCRIPTION

The UC184xA family of control ICs provides all the necessary features to implement off-line fixed-frequency, current-mode switching power supplies with a minimum of external components. The current mode architecture demonstrates improved load regulation, pulse-by-pulse current limiting and inherent protection of the power supply output switch. The IC includes: A bandgap reference trimmed to ±1% accuracy, an error amplifier, a current sense comparator with internal clamp to 1V, a high current totem pole output stage for fast switching of power MOSFET"s, and an externally programmable oscillator to set frequency and maximum duty cycle. The undervoltage lock-out is designed to operate with 250µA typ. start-up current, allowing an efficient bootstrap supply voltage design.

KEY FEATURES

■ LOW START-UP CURRENT. 0.5mA max.

■ TRIMMED OSCILLATOR DISCHARGE CURRENT. See Product Highlight

■ OPTIMIZED FOR OFF-LINE AND DC-TO-DC CONVERTERS.

■ AUTOMATIC FEED FORWARD COMPENSATION.

■ PULSE-BY-PULSE CURRENT LIMITING.

■ ENHANCED LOAD RESPONSE CHARACTERISTICS.

■ UNDER-VOLTAGE LOCKOUT WITH HYSTERESIS.

■ DOUBLE PULSE SUPPRESSION.

■ HIGH-CURRENT TOTEM POLE OUTPUT.

■ INTERNALLY TRIMMED BANDGAP REFERENCE.

■ 500KHz OPERATION.

■ LOW RO ERROR AMPLIFIER.

APPLICATIONS

■ ECONOMICAL OFF-LINE FLYBACK OR FORWARD CONVERTERS.

■ DC-DC BUCK OR BOOST CONVERTERS.

■ LOW COST DC MOTOR CONTROL.