Power Electronics
New LDO Suits Next-Generation Embedded Processors

New LDO Suits Next-Generation Embedded Processors

Microchip’s MCP1727 is a LDO voltage regulator that incorporates shutdown, power good, programmable power good delay and bond-wire compensation in a single chip. Fixed- and adjustable-output versions of the device are available. With this combination of features, the device is ideally suited for powering a variety of high-performance embedded processors and next-generation logic cores.



According to Qi Deng, senior product engineer with Microchip’s Analog and Interface Products Division, the motivation for developing the device was the trend in smaller-geometry processing technology that has created a new class of advanced CPUs and logic cores that require higher operating currents and lower core voltages. With output voltage down to 0.8 V and output current up to 1.5 A, this LDO is equipped to power these types of systems. The device’s typical dropout voltage of 330 mV at full load current and quiescent current of 120 µA contribute to its efficiency.



This part is similar to the MCP1726, which has a lower dropout voltage (220 mV) at full load and lower current capacity (1 A). Deng stated one key difference between these parts is that the voltage feedback input is provided through a separate pin and bond wire for both the fixed and adjustable versions of the MCP1727. This allows the voltage control loop to sample the voltage across the load while bypassing the voltage drop caused by the bond wire connected to the voltage output pin.



The resulting typical voltage regulation accuracy for the MCP1727 is 0.5%. Furthermore, the voltage control loop can be stabilized with a 1-μF ceramic output capacitor. The output voltage range of the device is from 0.8 V to 5.0 V for both the fixed and adjustable versions.



Current sensing and limiting for the pass device, an integrated PMOS transistor, is accomplished through a current mirror structure, according to Deng. The output of the current mirror is compared to an internal current source, limiting the output current to 3 A.



The power good output delay is user-programmable by the value of a single capacitor. This allows a broad range of power sequencing options.



The device also includes thermal protection. While the thermally capable 8-pin SOIC or 3 mm x 3 mm DFN packages allow for driving 1.5-A loads, internal overtemperature protection circuitry is designed to prevent the junction temperature of the device from reaching 150°C. Deng stated that a good design practice is to ensure the regulator will never approach this condition under anticipated worst-case conditions.



One way to accomplish this is through the use of the shutdown feature. This feature allows the LDO to be controlled by system control logic signals.



The MCP1727 is now available for sampling and volume production. Pricing is $1.26 each in 10,000-unit quantities for the 8-pin SOIC package, and $1.34 each in 10,000-unit quantities for the 3 mm x 3 mm, 8-pin DFN package.



Microchip also offers the MCP1726 1-A LDO Evaluation Board (Part # MCP1726EV) that can be used to support development using the MCP1727. The board enables designers to evaluate the MCP1727 with the power good output, shutdown input and power good delay features. It is available for $30.



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