The UC3842B, UC3843B series are high performance fixed

frequency current mode controllers. They are specifically designed for

Off?Line and DC?DC converter applications offering the designer

a cost?effective solution with minimal external components. These

integrated circuits feature a trimmed oscillator for precise duty cycle

control, a temperature compensated reference, high gain error

amplifier, current sensing comparator, and a high current totem pole

output ideally suited for driving a power MOSFET.

Also included are protective features consisting of input and

reference undervoltage lockouts each with hysteresis, cycle?by?cycle

current limiting, programmable output deadtime, and a latch for single

pulse metering.

These devices are available in an 8?pin dual?in?line and surface

mount (SOIC?8) plastic package as well as the 14?pin plastic surface

mount (SOIC?14). The SOIC?14 package has separate power and

ground pins for the totem pole output stage.

The UCX842B has UVLO thresholds of 16 V (on) and 10 V (off),

ideally suited for off?line converters. The UCX843B is tailored for

lower voltage applications having UVLO thresholds of 8.5 V (on) and 7.6 V (off).

特性 Features

? Trimmed Oscillator for Precise Frequency Control

? Oscillator Frequency Guaranteed at 250 kHz

? Current Mode Operation to 500 kHz

? Automatic Feed Forward Compensation

? Latching PWM for Cycle?By?Cycle Current Limiting

? Internally Trimmed Reference with Undervoltage Lockout

? High Current Totem Pole Output

? Undervoltage Lockout with Hysteresis

? Low Startup and Operating Current

? This is a Pb?Free and Halide?Free Device