27 March 2012
Power component suppliers look to develop integrated solutions as space concerns grow
A range of customer requirements, including efficiency, board space and cost, are pushing suppliers of embedded power components to develop devices with an application focus.
Brian Hedayati, vp of marketing for Micrel's analogue division, said: "One clear imperative is the need to focus on customer requirements by providing innovative solutions that get them going forward."
He sees a range of trends influencing the company's product development efforts. "Energy efficiency, heat and power are important; not only for primary power, but also for battery powered systems. In both cases, there is limited space to remove heat, so we need to offer components which have the highest efficiency under standby and low load conditions. And efficiency makes a huge difference to the cost of operation."
The drive to include more functionality in products is also impacting component developers. Hedayati said: "Designers are looking to add more features or to improve performance, but within the same footprint. This often involves the use of more components, so there is less space for power management devices."
The solution is to provide components with higher levels of integration and which need less design in time. "Often," said Hedayati, "designers don't want to work out how a part operates, they just want to plug it in."
Following a similar path is Enpirion, founded as a spin out from Lucent/Bell in 2001. Mark Cieri, director of business development and marketing, said: "Enpirion was founded to address high frequency issues; for example, 20MHz switching. This is important, because high frequency design enables high densities."
Enpirion specialises in integrated power management solutions. Amongst its product portfolio is a family of dc/dc converters featuring integrated inductors, bringing high efficiency, small footprint and low noise performance.
Cieri said: "A power supply on a chip means integrated inductors, voltage regulation, fets, controller and compensation loop."
Using its patented technology, Enpirion says its solution offers 10 times the power density of conventional devices, with 65% fewer components. Cieri claimed Enpirion's parts are typically 50% smaller than similar devices, with a lower profile. "And they have increased reliability, lower cost and need fewer external components."
Hedayati believes designers are looking for solutions that address particular challenges. "For example, loads changing at high rates. The system needs to handle transients and resonance without needing a lot of filtering capacitors."
Micrel is addressing integration issues through its Ripple Blocker technology. "It's something that removes noise and ripple from power supplies," Hedayati explained. "It's an active filter integrated into LDOs and load switches.
While it's a small device, it makes a big difference in a range of applications because it enhances system performance, saves component count and board space."
Micrel's MIC94300 Ripple-Blocker is said to simplify filter design by integrating a load switch with an active filter circuit to provide a clean output voltage. The load switch is controlled by an active high enable. Forcing the enable low turns off the load switch and sends it into a near 'zero' off mode current state. When enabled, the load switch is operated in its saturation region to maintain optimum performance. This results in fixed voltage drop of approximately 170mV between the input and output voltage.
It offers an attenuation factor of about 60dB from 30kHz to 10MHz – claimed by Micrel to be an order of magnitude better than an LC filter at the same switching frequency. The internal active filter passes dc and blocks any ac components with a frequency of more than 1kHz. A third order filter provides a steep roll off, so most of the attenuation is available from 30kHz to 10MHz.
Why should designers be interested in such solutions? Hedayati noted: "If you're capturing low level signals, you need a clean power supply which doesn't interfere with the measurements." While many applications can be found in the consumer electronics world – where space is at a premium – there is also interest from other sectors. "Anywhere you're dealing with low level signals," Hedayati contended, "including security cameras, barcode scanners and medical equipment."
The dc/dc switching regulator market is said to be a 'major focus' for Micrel. An example is the MIC94310, an LDO with Ripple Blocker technology which requires 56% less board space than a discrete solution. The monolithic device provides low frequency ripple attenuation to a regulated output voltage. Micrel says this is important in applications where the converter has to raise or lower a supply voltage, but where switching noise cannot be tolerated.
Micrel has also developed the SuperSwitcher range of dc/dc regulators. "These devices feature HyperSpeed technology," Hedayati pointed out, "which can increase frequency when there's a load transient, and HyperLight, in which the frequency drops to decrease losses."
HyperSpeed is a digitally modified adaptive on time control and ripple injection technique. The digital portion maintains a constant frequency during minor changes in the output current, but switches to constant on-time mode to provide fast transient response. This offers designers the choice of better transient response with the same amount of capacitance as a traditional PWM control scheme or lower output capacitance.
HyperLight provides the same performance as HyperSpeed when operating under heavy loads. However, it trades off constant frequency operation to maintain high efficiency at light loads – potentially 1% of full load current.
The control loop operates in full variable frequency mode but, as load current decreases, the device transitions to discontinuous condition mode. This brings high efficiency – typically in excess of 80%, says Micrel – at light loads and cuts power consumption when the system is idling.
Enpirion's latest offering is the EV1320, a 2A source/sink DDR termination converter that offers a peak efficiency of 96% – said to represent a saving of 1.4W over traditional LDO based solutions. "The EV1320 enables designers to reduce the memory subsystem's power dissipation significantly without resorting to more expensive, larger switching regulator based memory termination options," Cieri commented.
Using its Bell Labs heritage, Enpirion is focusing on materials technology. "We have a 1A product running at 20MHz," said Cieri, "and that means very small inductors. We have been working on developing proprietary materials – Fe/Si alloys – and can fab our own magnetics."
Enpirion has rolled through a number of product generations. In the first generation, it used wire wound magnetics mounted on laminates, but the fourth generation packaging features an integrated leadframe in which clips are used to create the inductor's windings. "Others use off the shelf inductors," Cieri explained. "We design ours to work in the package and to give high performance."
Cieri has termination power supplies in mind for the EV1320. "As industry moves to DDR4, there are problems powering Vtt," he said. "There are two solutions. One is the LDO. Here, when you cut the voltage, you cut efficiency to 50%. While LDOs are small and low noise, as the power decreases, power dissipation problems increase, so you're trading off against heat. Or you could use a discrete regulator. These have good efficiency, but are larger than LDOs and more expensive. We say you can get the best of both worlds."
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