The engineers who design linear regulator are doing their part to help portable products continue shrinking. Packages continue to get smaller while performance specs get better.
These devices trim overall size by squeezing two parts into a single package or by incorporating functions so fewer external parts are needed. Either way, linear regulators are helping make products more compact without sacrificing battery lifetimes.
Small parts have big specs
Micrel Inc. has packaged dual ultra-low dropout voltage ULDO linear regulators in a 1.6 × 1.6 mm 6-pin MLF package. Despite their small size, the parts have ultra-low dropout voltages of 35 mV at 150 mA and more than 70 db Power Supply Rejection Ratio. Engineers can reduce the footprint of their systems by 71 percent compared to standard 3 × 3 mm packages.
Both members of the line, the MIC5320 and MIC5321, deliver 117 mA per square mm which makes possible very compact form factor designs. The parts both feature low quiescent current, a fast turn-on time of 30 µsec, current limit and thermal shutdown protection, and can operate from -40 to 125C.
The ICs also offer the industry's lowest dropout for a 150 mA dual LDO, enabling longer battery life in portable applications with a Li-Ion battery. Pricing starts at $0.64 for 1K quantities.
Regulator reduces need for external components
A 100 mA low drop-out CMOS linear regulator from National Semiconductor Corp. is shipping in LLP packaging. The LP5900SD emits a low 6.5 µVRMS of noise without an external bypass capacitor, five times less than competing parts that require an external bypass capacitor. The LP5900SD is stable with just 0.47 µF of input and output capacitance, requiring two very tiny ceramic chip capacitors.
The LP5900SD also features a high power supply rejection ratio (PSRR) of 85 dB. The device, housed in a six-lead LLP package that measures 2.20 × 2.50 × 0.8 mm, features high power supply ripple rejection, consuming a mere 25 µA of quiescent current. A low 80 mV dropout improves system efficiency by enabling regulation from the lowest possible voltage source. Output voltage accuracy of ±2 perecent over the full line/load/temperature guarantees maximum performance of the signal-path device being powered.
Dual regulators fit incompact package
The LTC3446 from Linear Technology Corp. is a 1A, 2.25 MHz, synchronous buck regulator with two 300mA VLDOs in a single package.
The triple output regulator is designed for battery-powered systems, with an input voltage range of 2.5 to 5.5V. It can generate output voltages as low as 0.8V from the buck regulator and 0.4V for each of the VLDOs, levels used by low voltage DSPs and microcontrollers. An automatic Burst Mode feature reduces quiescent current to only 140 uA, maximizing battery run-time.
The buck regulator's 2.25 MHz switching frequency helps reduce the need for external components. The VLDO is house in a14-lead, 3 × 4 mm DFN package. Pricing starts at $2.75 each in 1,000-piece quantities.
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