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UC2825 Dataheets PDF



Part Number UC2825
Manufacturers Unitrode
Logo Unitrode
Description High Speed PWM Controller
Datasheet UC2825 DatasheetUC2825 Datasheet (PDF)

High Speed PWM Controller application INFO available UC1825 UC2825 UC3825 FEATURES • Compatible with Voltage or Current Mode Topologies • Practical Operation Switching Frequencies to 1MHz • 50ns Propagation Delay to Output • High Current Dual Totem Pole Outputs (1.5A Peak) • Wide Bandwidth Error Amplifier • Fully Latched Logic with Double Pulse Suppression • Pulse-by-Pulse Current Limiting • Soft Start / Max. Duty Cycle Control • Under-Voltage Lockout with Hysteresis • Low Start Up Current (1.

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


UC2823 UC2825 100182


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