UC2861N

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UC2861N is a high-performance current-mode control pulse width modulation (PWM) in a 16-pin package. The device features a built-in reference, error amplifier, and an 8 MHz oscillator. It provides a cost-effective solution for off-line and dc-to-dc fixed frequency current Mode control. UC2861N is a 3-terminal adjustable negative voltage regulator with specified thermal stability over a wide temperature range. It operates over a wide input voltage range from 2.5 V to 40 V, and is capable of providing a regulated negative output voltage, adjustable from 3 V to 17 V.

PMIC - AC DC Converters, Offline Switchers

The UC2861N can be used in a wide range of ac-to-dc converter and offline switcher applications, including SMPS (Switch Mode Power Supplies) and flyback converters. UC2861N is an ideal solution for off-line and dc-to-dc applications because of its fast transient response and low noise. Furthermore, the device features a built-in fixed frequency oscillator and low-cost current mode control schemes to optimize performance and efficiency.

Moreover, UC2861N can be used as an offline switcher with enhanced efficiency and transient response. The device offers a single feedback loop with minimum external components, as needed in offline switcher applications. Additionally, its flexible control scheme with wide operating frequency range allows it to be used in applications such as power-factor-correction (PFC) and wide range of output voltage (from 3 V to 17 V) applications.

Working Principle

The operating principle of UC2861N is based on current-mode control. It senses the pulses at peak current on the input side, and adjusts their magnitude to control the output voltage. The internal oscillator runs at a pre-set frequency of 8 MHz, and provides the switching element with a clock signal. The error amplifier senses the difference between the output voltage and its reference voltage, and sets the peak current magnitude that is required to keep the output voltage steady.

The UC2861N relies on the pulse-by pulse current limiting for overload protection. When the output voltage starts to fall, the voltage loop forces the output frequency to increase until the output current reaches its maximum limit. An additional protection is provided by the frequency fold-back feature. Frequency fold-back reduces the oscillator frequency when the current limit is exceeded, limiting the output power dissipation.

In summary, UC2861N is an ideal device for off-line and dc-to-dc applications due to its fast transient response and low noise. The device provides a single feedback loop with minimum external components, as needed in offline switcher applications. Its flexible control scheme with wide operating frequency range allows it to be used in applications such as power-factor-correction (PFC) and wide range of output voltage applications. Furthermore, the device features a built-in fixed frequency oscillator and low-cost current mode control schemes to optimize performance and efficiency.

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