uc3842bn 

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high performance current mode controller

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).
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