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.