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  • LMZ20501 1.0 A Simple Switcher

  • Created: Jul 11, 2016

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This reference design is a simple switcher Nano module regulator, which is identical to synchronous step down converter. It has an exceptional efficiency and accuracy that is capable of driving up to 1A of load from an input voltage of up to 5.5V. It uses the Texas Instruments’ LMZ20501 Nano regulator featuring an adjustable output voltage that ranges from 0.8V to 3.6V with current limit, thermal shutdown and UVLO protection.

The simple switcher is a voltage mode buck regulator with an integrated inductor. It has basically two operating modes, which allows user to tailor the regulator to their specific requirements. In forced PWM mode, the regulator operates as a full synchronous device with a 3MHz switching frequency and very low output voltage ripple. In AUTO mode, the regulator moves into PFM when the load current drops below the mode change threshold. Meanwhile in PFM, the device regulates the output voltage between wider ripple limits than in PWM. This results in much smaller supply current than in PWM, at light loads and high efficiency. In the circuit, the output capacitor C3 and C2, are adjusted for the best transient response and highest loop phase margin. However, it should be noted that output capacitance should be limited to 100uF to 200uF so it will not prevent the regulator from starting-up correctly.

This design incorporates world-class package technology to provide a 1A power supply with a total volume of only 21cu mm. It is a typical application of LMZ20501 Nano module regulator, which incorporates cycle-by-cycle peak current, limit on both the high and low side MOSFETs. This feature limits the output current in case the output is overloaded. During the overload, the peak inductor current is limited to that value found in the Electrical Characteristics table under the heading of "ILIM". Moreover, this design is typically used to convert a higher DC voltage to a lower DC voltage with a maximum output current of 1A. It is also suitable for point of load regulation and space constrained applications.



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