DESCRIPTION
The LX155X family of ultra-low start-up current (250µA max.), current mode control ICs offer new levels of energy efficiency for offline converter applications. They are ideally optimized for personal computer and CRT power supplies although they can be used in any number of off-line applications where energy efficiency is critical. Coupled with the fact that the LX155X series requires a minimal set of external components, the series offers an excellent value for cost conscious consumer applications.
Optimizing energy efficiency, the LX155X series demonstrates a significant power reduction as compared with other similar off-line controllers. Table 1 compares the SG384X, UC384XA and the LX155X start-up resistor power dissipation. The LX155X offers an overall 4X reduction in power dissipation. Additionally, the precise oscillator discharge current gives the power supply designer considerable flexibility in optimizing system duty cycle consistency.

KEY FEATURES
■ ULTRA-LOW START-UP CURRENT (150µA typ.)
■ TRIMMED OSCILLATOR DISCHARGE CURRENT (±2% typ.)
■ INITIAL OSCILLATOR FREQUENCY BETTER THAN ±4%
■ OUTPUT PULLDOWN DURING UVLO
■ PRECISION 2.5V REFERENCE (±2% max.)
□ CURRENT SENSE DELAY TO OUTPUT (150ns typ.)
□ 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 (±1Amp peak)
□ 500kHz OPERATION

APPLICATIONS
■ ECONOMY OFF-LINE FLYBACK OR FORWARD CONVERTERS
■ DC-DC BUCK OR BOOST CONVERTERS
■ LOW COST DC MOTOR CONTROL