UC2845AM Microchip

UC184xA / 284xA / 384xA CURRENT MODE PWM CONTROLLER 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 UC184xA family of control ICs provides externally programmable oscillator to set LOW START-UP CURRENT. all the necessary features to implement off-line frequency and maximum duty cycle. The (0.5mA max.) fixed-frequency, current-mode switching power undervoltage lock-out is designed to operate with TRIMMED OSCILLATOR DISCHARGE CURRENT. (See supplies with a minimum of external 250A typ. start-up current, allowing an efficient Product Highlight) components. The current mode architecture bootstrap supply voltage design. Available OPTIMIZED FOR OFF-LINE demonstrates improved load regulation, pulse- options for this family of products, such as start- AND DC-TO-DC by-pulse current limiting and inherent protection up voltage hysteresis and duty cycle, are CONVERTERS. of the power supply output switch. The IC summarized below in the Available Options AUTOMATIC FEED FORWARD includes: A bandgap reference trimmed to 1% section. The UC184xA family of control ICs is COMPENSATION. accuracy, an error amplifier, a current sense also available in 14-pin SOIC package which PULSE-BY-PULSE CURRENT comparator with internal clamp to 1V, a high makes the Power Output Stage Collector and LIMITING. current totem pole output stage for fast Ground pins available. ENHANCED LOAD RESPONSE switching of power MOSFET s, and an CHARACTERISTICS. UNDER-VOLTAGE LOCKOUT IMPORTANT: For the most current data, consult MICROSEMIs website: PRODUCT DA TABOOK 1996/1997 UC184xA/284xA/384xA C URRENT MODE PWM CONTROLLER P RODUCTION D ATA S HEET PACKAGE PIN OUTS ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (Low Impedance Source) (V ) ......................................................... 30V CC COMP 1 8 V REF Supply Voltage (I < 30mA).......................................................................... Self Limiting CC V 27 V FB CC Output Current............................................................................................................. 1A I 36 OUTPUT SENSE Output Energy (Capacitive Load)................................................................................. 5J R /C 45 GND T T Analog Inputs (V & I ) ........................................................................ -0.3V to +6.3V FB SENSE M & Y PACKAGE Error Amp Output Sink Current ............................................................................... 10mA (Top View) Power Dissipation at T = 25C (M Package) .............................................................. 1W A Storage Temperature Range .................................................................... -65C to +150C Lead Temperature (Soldering, 10 Seconds) ............................................................. 300C 1 8 COMP V REF Peak Package Solder Reflow Temp. (40 second max. exposure)..........................................260C (+0, -5) 27 V V FB CC Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect 36 I OUTPUT SENSE to Ground. Currents are positive into, negative out of the specified terminal. Pin 45 R /C GND T T numbers refer to DIL packages only. DM PACKAGE THERMAL DATA (Top View) M PACKAGE: THERMAL RESISTANCE-JUNCTION TO AMBIENT, 95C/W COMP 1 14 V JA REF N.C. 213 N.C. DM PACKAGE: V 312 V FB CC 165C/W THERMAL RESISTANCE-JUNCTION TO AMBIENT, N.C. 411 V JA C I 510 OUTPUT SENSE D PACKAGE: N.C. 69 GND THERMAL RESISTANCE-JUNCTION TO AMBIENT, 120C/W R /C 78 PWR GND JA T T Y PACKAGE: D PACKAGE THERMAL RESISTANCE-JUNCTION TO AMBIENT, 130C/W (Top View) JA RoHS / Pb-free 100% Matte Tin Lead Finish = T + (P x ). Junction Temperature Calculation: T J A D JA The numbers are guidelines for the thermal performance of the device/pc-board system. JA All of the above assume no ambient airflow Copyright 1995 2 Rev. 1.2a 10/25