UC3845D8TR Integrated Circuits (ICs)

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UC3845D8TR is a monolithic, fixed–frequency current–mode Pulse-Width Modulation (PWM) voltage regulator control IC. This controller includes advanced features to realize stable and low-cost DC-DC converters.

Application Field

UC3845D8TR is widely used in many applications, such as HVAC/R appliances, DC Motor Controllers, Active and Standby power supplies, Variable Speed Drives, Uninterrupted Power Supplies, Battery Chargers, and Lighting Control.

Working Principle

The UC3845D8TR is designed with a fixed frequency current mode PWM control architecture. The primary control loop senses the output voltage between the FB and the GND pins, and the output reference voltage is compared with the detected voltage of the output voltage. The integrated error amplifier produces and error signal which is compared with the internally generated triangle wave oscillator signal. A duty cycle signal is generated, and then the power-switching output devices are controlled. The feedback signal is routed through a voltage divider to the FB terminal, thereby allowing the loop to regulate the output voltage. The UC3845D8TR can easily be used in a wide range of DC-DC converter topologies, such as flyback, forward, push-pull and SEPIC.

Protection Features

The protection features of the UC3845D8TR provide reduce of the stress in the output stage and the higher reliability of the system. The protection features include the cycle-by-cycle current limit, Under Voltage Lockout (UVLO), and the following shutdown conditions: Over Voltage (OVP), Under Voltage, Cycle–by–Cycle Over Current (OCP), and sense Over Current (SOC). The OCP and the SOC provide an additional level of protection without an external component to sense the drain current and respectively the current run–away avoidance.

IC Characteristics

The UC3845D8TR has low start-up current and low standby current to minimize power dissipation, and high input voltage capability. The device provides a wide voltage range from 8V to 45V, 75mA peak output current, precision reference, guaranteed ±5% over temperature, low operating temperature range of -25 C to +125 C, and programmable blanking intervals. The current–mode runs in the synchronization range of 300kHz to 500kHz.

Conclusion

UC3845D8TR is a high performance, monolithic, fixed–frequency current mode PWM voltage regulator control IC. It is suitable for a wide range of DC-DC converter topologies. This controller can be used in many applications, such as HVAC/R appliances, DC Motor Controllers, Active and Standby power supplies, Variable Speed Drives, Uninterrupted Power Supplies, Battery Chargers, and Lighting Control. The UC3845D8TR also provides protection features and excellent performance characteristics.

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