Susie Maestre

user Electronics Engineer

city Innovuze Solutions Inc.

  • Buck Converter with LDO Regulator at 500kHz Switching Frequency

  • Created: Apr 12, 2016

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This reference design features the TPS65321-Q1 device from Texas Instruments, which is a combination of a buck converter and a low-dropout regulator. This is designed to operate at a 500kHz switching frequency. The input voltage ranges from 3.6V-36V for the buck converter, and 3V-36V for the LDO regulator. The buck regulator has an integrated high side MOSFET and an active low, open-drain output pin (nRST). On the other hand, the LDO regulator has also an integrated MOSFET and features a low-input current of 35uA in no load condition.

In this design, resistor R5, which is connected on the RT/CLK pin, determines the switching frequency. The RT/CLK pin voltage has a typical voltage of 0.5V. The buck regulator provides a flexible design to fit system needs. The external loop compensation circuit, which is connected to the COMP pin, allows for optimization of the converter response for the appropriate operating conditions. This COMP pin is the error-amplifier output of the buck regulator and the input to the output switch-current comparator of the buck regulator. Further in this design, a bootstrap capacitor is placed between the BOOT and SW pins to supply bias voltage for the integrated high side MOSFET. The enable pins EN1 and EN2 of the buck and LDO regulators respectively are connected together, and are pulled externally to enable both the buck and the LDO regulators.

The nature of the IC, which integrates both the buck and linear regulators, makes the design useful in applications that require both a buck converter and linear regulator. This design is also essential in automotive infotainment and cluster, Advanced Driver Assistance System (ADAS), automotive telematics, eCall, and 12-V and 24-V industrial, commercial, low power systems.