1 Features
1• Peak Current Mode, Average Current Mode, or
Voltage Mode (With FeedForward) Control
Methods
• Practical Operation Up to 1 MHz
• 50-ns Propagation Delay to Output
• ±1.5-A Peak Totem Pole Outputs
• 9-V to 30-V Nominal Operational Voltage
• Wide Bandwidth Error Amplifier
• Fully Latched Logic With Double Pulse
Suppression
• Pulse-by-Pulse Current Limiting
• Programmable Maximum Duty Cycle Control
• Undervoltage Lockout With Hysteresis
• Trimmed 5.1-V Reference With UVLO
• Same Functionality as UC3823 and UC3825

2 Applications
• Off-Line and DC-DC Power Supplies
• Converters Using Voltage Mode, Peak Current
Mode, or Average Current Mode Control Methods
• Single-Ended or Two-Switch Topology Designs

3 Description
The UC28023 and UC28025 are fixed-frequency
PWM controllers optimized for high-frequency
switched-mode power-supply applications. The
UC28023 is a single output PWM for single-ended
topologies while the UC28025 offers dual alternating
outputs for double-ended and full bridge topologies.
Targeted for cost-effective solutions with minimal
external components. UC2802x devices include an
oscillator, a temperature compensated reference, a
wide bandwidth error amplifier, a high-speed currentsense
comparator, and high-current, active-high,
totem-pole outputs to directly drive external
MOSFETs.
Protection circuitry includes a current limit comparator
with a 1-V threshold, a TTL compatible shutdown
port, and a soft-start pin which doubles as a
maximum duty-cycle clamp. The logic is fully latched
to provide jitter-free operation and prohibit multiple
pulses at an output. An undervoltage lockout section
with 800 mV of hysteresis assures low start-up
current. During undervoltage lockout, the outputs are
high impedance. Propagation delays through the
comparators and logic circuitry have been minimized
while maximizing bandwidth and slew rate of the error
amplifier.
Devices are available in the industrial temperature
range of –40°C to 105°C. Package offerings are
16-pin SOIC (DW), or 16-pin PDIP (N) packages.