UC3845BNG

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UC3845BNG is an integrated circuit (IC) from Texas Instruments which belongs to the type of Switched-Mode Power Supply (SMPS) controllers. It is an enhancement of UC3845B and is typically used to implement switching mode converter applications. It has an on-chip 3-terminal adjustable regulator suitable for power sources up to 20V and contains necessary features for pulse-width modulation for controlling power carrievers.

UC3845BNG is a DC/DC switching controller that provides all the necessary features to design a step-down (buck), step-up (boost), flyback, or a forward converter. It has additional low-side drivers, like open drain and totem-pole output, which enables it to control the power switches of the design with more flexibility. This device can be used in a wide range of applications, such as offline fixed-frequency wired power supplies, DC/DC converters, panel displays, mainframe power systems, and digital microprocessor-controlled power supplies.

The working principle of UC3845BNG is based on a comparison between two voltage signals: an error voltage, and a sawtooth voltage. When the error voltage is higher than the sawtooth voltage, the output driver is disabled, and the controller remains in charge pump mode to refresh the timing capacitor. When the error voltage is lower than the sawtooth voltage, the output driver is enabled and the MOSFETs of the power stage switch.

The output voltage level of a DC/DC switching converter is determined by the applied duty cycle of the pulse width modulation (PWM) signal that is generated by the controller. The duty cycle is set by an external feedback divider which gives a certain error voltage to the comparator input. The voltage is compared to a sawtooth ramp generated internally at regular intervals by an oscillator operating at a fixed frequency. Each time the error voltage exceeds the sawtooth level the output switches off, until the error voltage drops below the sawtooth voltage.

In addition to controlling the output of the power stage, this controller can also be configured to provide a wide range of protections, like under-voltage lockout, current limiting, and thermal shut down. This IC also features soft-start structures, peak current-mode control loop, pulse-by-pulse current limiting and an auxiliary winding clamp to limit the voltage stress on the power switches. Additionally, this device can maintain a consistent frequency operation even when the output load and supply voltage are changed or an extremely light or no load condition exists.

UC3845BNG is a highly reliable and effective DC/DC switching controller that can be used for a wide range of applications. It provides a number of features to ensure a safe and reliable operation with maximum power efficiency. With its wide range of inputs and outputs, it has become the go-to controller for digital microprocessor-controlled power supplies, panel displays, mainframe power systems, and many more.

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