TL3845PG4

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TL3845PG4 application field and working principle

The TL3845PG4 is a high-performance, PWM dc/dc switching controller from Texas Instruments, designed for flyback and forward converter control applications. It is used for step-down and step-up operations. The device supports low-cost, high-performance voltage-regulation designs, and could be used in 9W and above power applications. It features a two-pin enable, current-limit protection, and clock synchronization.

Features

• Wide operating voltage: 2.7V to 16V
• Two-pin enable
• Low total component count
• PWM mode: Frequency up to 500kHz
• Error amplifier bandwidth TBD
• Current-limit protection
• External clock synchronization

Applications

• Power supplies for personal computers (PCs); DSP and ASIC power supplies
• Battery-powered devices
• Portable DVD players and digital cameras
• DC/DC converters for telecom and automotive applications

Working Principle

The TL3845PG4 works according to the pulse-width modulation technique. It receives an analog (or digital) input voltage, and produces an output voltage in response to that input voltage. The output voltage is a duty cycle signal that has the same duty cycle as the input voltage, but has a different amplitude.

The output voltage\'s duty cycle can be adjusted. A higher duty cycle reduces the output voltage, while a lower duty cycle increases it. The duty cycle is controlled by an internal current-limit circuit that monitors the current in the output inductor. When the current in the inductor reaches the maximum current-limit threshold, the controller will reduce the duty cycle, thereby reducing the amount of energy supplied to the inductor and thus reducing the load current.

The TL3845PG4 also has a two-pin enable feature which can be used to reduce power consumption when the circuit is not in use. This feature is often referred to as "sleep mode". When the enable pin is asserted, the TL3845PG4 will reduce the output voltage to a safe minimum level. When the enable pin is de-asserted, the TL3845PG4 will restore the output voltage to the previous level.

The TL3845PG4 supports external clock synchronization. When in external clock synchronization mode, the TL3845PG4 will generate the output voltage in step with the external clock signal. The synchronization signal must be below the PWM inverse frequency to prevent the output voltage from becoming too high. This feature is useful when a system needs to be powered up on a consistent voltage and current level.

Conclusion

The TL3845PG4 is a high-performance, PWM dc/dc switching controller designed for flyback and forward converter control applications. It supports low-cost, high-performance voltage-regulation designs, and could be used in 9W and above power applications. It features a two-pin enable, current-limit protection, and clock synchronization, making it an ideal solution for powering portable devices, PCs, and digital cameras. In addition, the TL3845PG4 allows the output voltage to be synchronized with an external clock, making it helpful in telecom and automotive applications.

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