UC3851N

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UC3851N is an extremely versatile controller IC for regulating the power of offline ACDC converters and also for regulating the power of offline switchers. It builds on the proven technologies of its predecessors and comes in a wide range of packages, including 4 and 6-pin Plastic Encapsulated Devices (PDE), 8 and 10-pin Plastic Quad Flat Packs (PQFP), and 12 and 14-pin Thick and Thin Quad Flat Pack (TQFP) packages. It is designed using advanced Analog and Mixed-Signal integrated circuit technology. The flexible architecture and wide range of features provide users with the flexibility and performance they have come to expect from a modern controller IC.

The UC3851N has several main functions. It can be used as either a voltage mode or current mode controller, depending on the configuration of the external circuitry. In voltage mode, it can be used for a wide range of buck, boost, forward and flyback designs, whereas in current mode it can be used for a range of resonant and discontinuous mode converters. It also has several control options, including fixed frequency, variable frequency control, soft start, burst mode operation and frequency fold back.

The UC3851N is built around a high-speed error amplifier, ramp generator, comparator and power MOSFET gate driver. The error amplifier compares an external voltage reference to the output voltage of the converter and the ramp generator generates a sawtooth wave that is compared to the output of the error amplifier. The comparator then produces an output signal that is used to control the power MOSFET switch.

The UC3851N also has a variety of protection features, including over-temperature protection, undervoltage lockout, auto-restart and over-voltage protection. The over-temperature protection prevents the IC from operating in an unsafe region by limiting the output voltage of the error amplifier in the presence of excessive temperatures. The undervoltage lockout ensures that the IC will not turn on unless the input voltage is above the minimum operating voltage, while the auto-restart feature allows the IC to be restarted if it is disabled due to a fault condition. Finally, the over-voltage protection ensures that the IC does not sustain damage in the presence of excessive voltages.

In addition, the UC3851N also has a built-in oscillator, which allows the user to set the operating frequency of the converter. The frequency is adjustable over a range of 500kHz to 3MHz, and the frequency is set using external capacitors and resistors. The frequency settings can also be changed by external logic if necessary.

In conclusion, the UC3851N is a versatile controller IC for regulating the power of offline ACDC converters and also for regulating the power of offline switchers. It is built on advanced analog and mixed-signal technology and provides users with the flexibility and performance they have come to expect from a modern controller IC. Its wide range of functions and protection features make it a great choice for come ACDC and offline switcher applications.

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