LX1552/3/4/5 U LTR A-L OW S TAR T-U P C URREN T , C U RRENT-M ODE PWM P RODU C T ION D AT A S HEET T HE I NFI N ITE P O W ER OF I N NOVATIO N KEY FEATURES DESCRIPTION The LX155x family of ultra-low start-up current Additionally, the precise oscillator discharge Ultra-Low Start-up Current (150A (250A max), current mode control ICs offer new current gives the power supply designer Typical) levels of energy efficiency for offline converter considerable flexibility in optimizing system duty Trimmed Oscillator Discharge applications. They are ideally optimized for cycle consistency. Current (2% Typical) personal computer and CRT power supplies The current mode architecture demonstrates Initial Oscillator Frequency Better Than 4% although they can be used in any number of off-line improved load regulation, pulse by pulse current Output Pulldown During UVLO applications where energy efficiency is critical. limiting and inherent protection of the power Precision 2.5V Reference (2 Coupled with the fact that the LX155x series supply output switch. The LX155x includes a maximum) requires a minimal set of external components, the bandgap reference trimmed to 1%, an error Current Sense Delay to Output series offers an excellent value for cost conscious amplifier, a current sense comparator internally (150ns Typical) consumer applications. clamped to 1V, a high current totem pole output Automatic Feed Forward Optimizing energy efficiency, the LX155x series stage for fast switching of power MOSFETs, and Compensation demonstrates a significant power reduction as an externally programmable oscillator to set Pulse-by-Pulse Current Limiting compared with other similar off-line controllers. operating frequency and maximum duty cycle. Enhanced Load response Table 1 compares the SG384x, UC384xA and the The under voltage lock-out circuitry is designed to Characteristics LX155x start-up resistor power dissipation. The operate with as little as 250A of supply current Under-Voltage Lockout with LX155x offers an overall 4X reduction in power permitting very efficient bootstrap designs. Hysteresis dissipation. Double Pulse Suppression High Current Totem Pole Output IMPORTANT: For the most current data, consult MICROSEMIs website: PRODUCT D A TABOOK 1996/1997 LX1552/3/4/5 ULTRA-LOW START-UP CURRENT, CURRENT-MODE PWM P RODUCTIO N D ATA S HEET ABSOLUTE MAXIMUM RATINGS (Note 1) PACKAGE PIN OUTS Supply Voltage (Low Impedance Source).................................................................. 30V Supply Voltage (I < 30mA)......................................................................... Self Limiting COMP 1 8 V REF CC V 27 V Output Current............................................................................................................. 1A FB CC I 36 OUTPUT SENSE Output Energy (Capacitive Load) ................................................................................ 5J R /C 45 GND T T Analog Inputs (Pins 2, 3) ........................................................................... -0.3V to +6.3V Error Amp Output Sink Current............................................................................... 10mA M & Y PACKAGE Power Dissipation at T = 25C (DIL-8) ...................................................................... 1W (Top View) A M Package RoHS / Pb-free 100% Matte Tin Lead Finish Operating Junction Temperature Ceramic (Y Package) ............................................................................................ 150C COMP 1 8 V REF Plastic (M, DM, D, PW Packages) ........................................................................ 150C V 27 V FB CC Storage Temperature Range .................................................................... -65C to +150C I 36 OUTPUT SENSE Lead Temperature (Soldering, 10 Seconds) ............................................................ 300C R /C 45 GND T T Pb-free / RoHS Peak Package Solder Reflow Temp. (40 second max. exposure)................ 260C (+0, -5) DM PACKAGE Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect (Top View) to Ground. Currents are positive into, negative out of the specified terminal. Pin RoHS / Pb-free 100% Matte Tin Lead Finish numbers refer to DIL packages only. 1 14 COMP V THERMAL DATA REF 2 13 N.C. N.C. 3 12 V V FB CC M PACKAGE: 4 11 N.C. V C 95C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, 5 10 I OUTPUT JA SENSE 69 N.C. GND DM PACKAGE: 78 R /C PWR GND T T THERMAL RESISTANCE-JUNCTION TO AMBIENT, 165C/W JA D PACKAGE D PACKAGE: (Top View) RoHS / Pb-free 100% Matte Tin Lead Finish 120C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA Y PACKAGE: N.C. 1 20 N.C. 2 19 130C/W N.C. N.C. THERMAL RESISTANCE-JUNCTION TO AMBIENT, JA 3 18 COMP V REF PW PACKAGE: 4 17 V N.C. FB 5 16 THERMAL RESISTANCE-JUNCTION TO AMBIENT, 144C/W N.C. V JA CC 6 15 I V SENSE C = T + (P x ). Junction Temperature Calculation: T 7 14 N.C. OUTPUT J A D JA The numbers are guidelines for the thermal performance of the device/pc-board system. 8 13 R/C GND JA TT 9 12 All of the above assume no ambient airflow N.C. PWR GND 10 11 N.C. N.C. PW PACKAGE (Top View) RoHS / Pb-free 100% Matte Tin Lead Finish Copyright 1994 2 Rev. 1.0b OBSOLETE PRODUCT NOT RECOMMENDED FOR NEW DESIGNS