Low dropout regulators deliver more power to the portable world

Power Electronics / Power Management

4 July 2001 Power Electronics / Power Management

Today's increasingly portable world is calling for new ways to regulate voltage while meeting space and high-volume cost demands. The answer, says Analog Devices, lies in its line of anyCAP low dropout regulators (LDOs), that deliver high accuracy, low dropout and stability with any type of output capacitor, including MLCC.

The anyCAP range allows maximum design flexibility, minimum footprint and true system-level benefits that include longer battery life, increased time between charges and the opportunity to use a smaller battery stack. Housed in one of the smallest thermally-enhanced package sizes available - incorporating proprietary leadframe design - these LDOs dissipate up to 30% more power, while considerably shrinking system size.

Figure 1. The anyCAP control loop

New topology

The anyCAP uses a patented, new topology - a single loop for regulation and reference functions. This single loop is controlled by a very high gain error amplifier. A unique noninverting driver between the error amplifier and the pass transistor is designed specifically to enable the frequency compensation to include the load capacitor in a pole-splitting arrangement, achieving reduced sensitivity to the value, type and ESR of the load capacitance.

Figure 2. In a cellular phone that operates off three fully discharged NiMH batteries, anyCAP LDOs provide an accurate output of 2,7 V from a 3,0 V ±10% input. Industry standard devices require a fourth NiMH battery to obtain the same minimum output voltage

As low as Zero ESR

Most LDOs place strict requirements on the range of ESR values for the output capacitor because they are difficult to stabilise due to the uncertainty of load capacitance and resistance. Moreover, the ESR value required to keep conventional LDOs stable changes depending on load and temperature. These ESR limitations make designing with other LDOs more risky and more difficult due to unclear specifications based on typical ESR values.

The anyCAP LDOs have no restraints on minimum ESR. The innovative design enables stability even with an MLCC and capacitor values as low as 0,47 mF. The very high regulator gain also leads to excellent line and load regulation with ±1,4% overall accuracy - one of the best in the industry.

Advanced features

With additional features such as a dropout detector, optional noise reduction, current and thermal limiting and a low shutdown current, designers have more ways to improve their portable designs. The anyCAP LDOs come in a variety of output voltages - as well as output current options.

For further information, contact CST Electronics, (011) 452 0706.

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Power Electronics / Power Management

Low dropout regulators deliver more power to the portable world

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