TOP257PG

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The TOP257PG is a versatile, wide-voltage range, high-efficiency, easy-to-use and easy-to-implement integrated switching regulator. The device is targeted for replacement of various offline SWITCHMODE power supplies (SMPS). With its integrated power switching, the TOP257PG can efficiently and economically provide the regulated output required for many different types of applications.

TOP257PG application field and working principle:

The TOP257PG is specifically designed to provide a complete primary side switchmode power supply solution for off-line non-isolated AC/DC converters and stand-alone offline switching regulators. The TOP257PG offers an integrated high voltage power MOSFET, current-mode control, wide-range line compensation, Enhanced Light Load Efficiency (LEL), high efficiency, and integrated output voltage feedback voltage. Applications of the TOP257PG include but are not limited to, cellular products, routers, modems, external storage, CCTV cameras and LED lighting applications.

The working principle of the TOP257PG is based on a pulse-width-modulation (PWM) in combination with a quasi-resonant (QR) topology, where a primary-side switch and a transformer provide a basic power-factor-correction, combined with good efficiency. Due to the low audible noise, the TOP257PG is especially suitable for small to mid-range, end-products with strict acoustic noise requirements.

The TOP257PG consists of an on-chip oscillator, an error amplifier, an on-chip power switch, an output voltage feedback, and a low harmonic distortion waveform shaping circuit. The enabled/drawable transformer allows the user to easily integrate a transformer with tight/cost sensitive applications. Unlike other conventional switchers, the TOP257PG starts up into skip mode with a burst-mode frequency at the beginning, and if the load requires a higher current, the device will transition to a fixed full-bridge mode.

The TOP257PG provides internal leading edge blanking (LEB) and trailing edge blanking (TEB) along with optimized frequency synchronization from 10kHz to 350kHz. Additionally, the TOP257PG provides a very low off-time with interleaving of both channels such that the critical conduction losses can be minimized. The TOP257PG also incorporates an Enhanced Light Load Efficiency (ELLE) sub-system that reduces the power lost in light-load conditions, allowing for improved overall efficiency versus traditional designs.

The TOP257PG offers excellent line regulation, which is typically less than 5%, and the output voltage ranges from 0.9V to 7V. Output voltage accuracy is typically 2.5%. With its integrated power switching and wide operating range, the TOP257PG is able to provide the regulated output required for various AC/DC applications.

The TOP257PG also has the advantage of an internal soft-start function, which reduces in-rush current and prevents the onset of overload conditions. The soft-start circuit needs an external R-C network for programming. With the built-in short circuit protection and thermal shutdown, it is also very safe and reliable. The TOP257PG also includes a shutdown input pin that can be used to shut down the circuit when not in use.

In conclusion, the TOP257PG is an efficient, cost effective, and easy-to-implement integrated switching regulator targeted for replacement of various offline SWITCHMODE power supplies. The device is highly efficient and provides excellent line regulation with a wide operating range, making it ideal for use in a variety of AC/DC converter and offline switching regulator applications.

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