application INFO available UC1825 UC2825 UC3825 High Speed PWM Controller FEATURES * * * * * * * * * * DESCRIPTION Compatible with Voltage or Current Mode Topologies The UC1825 family of PWM control ICs is optimized for high frequency switched mode power supply applications. Particular care was given to minimizing propagation delays through the comparators Practical Operation Switching Frequencies and logic circuitry while maximizing bandwidth and slew rate of the to 1MHz error amplifier. This controller is designed for use in either cur50ns Propagation Delay to Output rent-mode or voltage mode systems with the capability for input voltage feed-forward. High Current Dual Totem Pole Outputs (1.5A Peak) Protection circuitry includes a current limit comparator with a 1V threshold, a TTL compatible shutdown port, and a soft start pin Wide Bandwidth Error Amplifier which will double as a maximum duty cycle clamp. The logic is fully Fully Latched Logic with Double Pulse latched to provide jitter free operation and prohibit multiple pulses at Suppression an output. An under-voltage lockout section with 800mV of hysteresis assures low start up current. During under-voltage lockout, the outPulse-by-Pulse Current Limiting puts are high impedance. Soft Start / Max. Duty Cycle Control These devices feature totem pole outputs designed to source and sink high peak currents from capacitive loads, such as the gate of a Under-Voltage Lockout with Hysteresis power MOSFET. The on state is designed as a high level. Low Start Up Current (1.1mA) BLOCK DIAGRAM UDG-92030-2 SLUS235A - MARCH 1997 - REVISED MARCH 2004 UC1825 UC2825 UC3825 CONNECTION DIAGRAMS ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (Pins 13, 15) . . . . . . . . . . . . . . . . . . . . . . . . 30V Output Current, Source or Sink (Pins 11, 14) DC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5A Pulse (0.5 s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0A Analog Inputs (Pins 1, 2, 7). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 7V (Pin 8, 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6V Clock Output Current (Pin 4) . . . . . . . . . . . . . . . . . . . . . . . -5mA Error Amplifier Output Current (Pin 3) . . . . . . . . . . . . . . . . 5mA Soft Start Sink Current (Pin 8) . . . . . . . . . . . . . . . . . . . . . 20mA Oscillator Charging Current (Pin 5) . . . . . . . . . . . . . . . . . . -5mA Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W Storage Temperature Range . . . . . . . . . . . . . . -65C to +150C Lead Temperature (Soldering, 10 seconds) . . . . . . . . . . 300C DIL-16 (Top View) J or N Package PLCC-20 & LCC-20 (Top View) Q & L Packages SOIC-16 (Top View) DW Package PACKAGE PIN FUNCTION FUNCTION PIN N/C INV NI E/A Out Clock N/C RT CT Ramp Soft Start N/C ILIM/SD Gnd Out A Pwr Gnd N/C VC Out B VCC VREF 5.1V THERMAL RATINGS TABLE Package DIL-16J DIL-16N PLCC-20 LCC-20 SOIC-16 QJA 80-120 90(1) 43-75(1) 70-80 50-120(1) QJC 28(2) 45 34 20(2) 35 Q Q 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 UC1825 UC2825 UC3825 ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for , RT = 3.65k, CT = 1nF, VCC = 15V, -55C