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)


Application

Audio
Automotive
Broadband
Digital Control
Military
Optical Networking
Security
Telephony
Video & Imaging
Wireless


Pinout




Specifications

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. . . . . . . . . . . . . . -65°C to +150°C
Lead Temperature (Soldering, 10 seconds) . . . . . . . . . . 300°C


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.