Mini-PMUs meet rapidly evolving power demands

Mini-PMUs meet rapidly evolving power demands

Mini-PMUs offer designers the ability to extend existing system functionality and take advantage of cost and space benefits

BY BILL WEISS
Advanced Analogic Technologies
Sunnyvale, CAhttp://www.analogictech.com

Take a look at today’s popular portable electronics devices and it’s easy to see how crucial a role functional integration has played in their success. Handsets that fit into the palm of a hand, MP3 players that slide into a shirt pocket, and Bluetooth devices that, weighing just a few ounces, can comfortably hang on an ear vividly illustrate how successful designers have been in collapsing multiple functions into smaller and smaller footprints.

When most consumers think of these rapid advances in product design, they invariably think of the progress IC manufacturers have achieved in digital integration. But clearly much of the credit for the rapidly shrinking footprint of today’s popular electronics devices must also be attributed to the use of complex power management units (PMUs). By collapsing multiple power circuits into a single device capable of managing functions as far ranging as display backlighting, battery charging, powering noise-sensitive RF circuits, and DSPs, these large, highly integrated PMUs have played a key role in today’s digital revolution.

At the same time it is a widely accepted axiom in the electronics industry that fast time to market is mandatory. Design teams that deliver a new technology to market before their competitors usually win larger market share and maximize profitability. That, in turn, increases a company’s probability of earning back its substantial up-front investment in R&D and, eventually, developing more new products. Accordingly, many argue that shortening the development cycle has a direct impact on the long-term survivability of any company in today’s competitive electronics market.

The question for many design teams today is how to reconcile the disparate requirements for high integrations and fast time to market for market success. Customer requirements for smaller and lower-cost products demand higher levels of functional integration. But the larger and more complex a PMU, the more up-front planning and design time it requires. In addition, the more functions a design team integrates into a PMU, the more specific its potential application. Ultimately, that fact places tremendous pressure on a design team to anticipate future product feature trends.

Today’s rapidly changing consumer markets make that a very difficult task. Often a design team must add new functionality on short notice to meet a new customer demand or to extend an existing product line with a new, emerging technology. As an example, the introduction over recent years of Wi-Fi capability and the development of affordable Bluetooth devices offered cellular handset designers exciting new functionality options if they could deliver their product to market quickly. Similarly, the current rollout of HD radio offers designers a new opportunity to extend the feature set of MP3 players, portable GPS devices, and other products. The key question for many portable electronics design teams today is, how can they capitalize on the new market opportunities these technological advances present and still maximize the benefit of cost and space savings that functional integration offers?

Assessing design options

Traditionally designers adding new functionality to an existing device could power those functions in either of two ways. Take as an example a design team of a successful personal navigation device (PND) that suddenly realizes it needs to add Bluetooth capability to stay competitive. Let’s assume the existing product uses a large PMU to power all existing functions. In this case, the designers can recast their existing design and replace their existing PMU with another device that integrates the additional step-down converter and low dropout linear regulators (LDOs) needed to support Bluetooth capability. This strategy will ultimately offer the smallest footprint and maybe the lowest cost of any option. But it also entails significant market risk. The time needed to specify a new PMU and respin the entire design could cost the manufacturer precious market share.

Alternately, the designers can add a discrete step-down converter and discrete LDOs to meet this new functional requirement. Many power IC manufacturers, for example, offer discrete step-down converters ideally sized for these applications. Some come in packages as small as 2 x 2 mm. At the same time designers can find from multiple vendors a wide variety of discrete LDOs offering low noise and active filtering. This discrete approach offers designers maximum flexibility. They can introduce this new capability in an extension to their product line and still leverage their existing design. But the addition of new discrete components will invariable drive up BOM cost and increase board space requirements.

Today designers have a third option. Rather than spend the time revising their existing design or introducing multiple new discrete power components, they can rapidly add new functionality by adding a mini-PMU to their design. New devices such as AnalogicTech’s AAT2504, combine an 800-mA step-down converter with two 300-mA LDOs, each with its own independent input, on a single IC. Its step-down converter offers power efficiency in the 95% range, and the LDOs provide can post regulate from the step-down converter.

This approach allows designers to add new functionality, such as Bluetooth capability, quickly without recasting their existing design. At the same time, it gives designers the chance to take advantage of functional integration by using fewer components and less board space than a pure discrete approach. Ultimately, this compromise option allows designers to meet the consumer market’s demanding cost and footprint requirements, simplify the board layout of the new function, and still deliver their new product to market quickly.

Mini-PMUs such as the AnalogicTech AAT2504 combine an 800-mA step-down converter with two 300 mA LDOs.

This strategy is not limited to the AAT2504. A wide and growing array of mini-PMU options is now available. Devices are available with single and multiple dc/dc converters, single and multiple LDOs in a broad array of combinations, and some with lithium-ion battery chargers. Most devices offer high levels of power efficiency across the entire load range and low quiescent current to help extend battery life.

For more on power management units, visit http://electronicproducts-com-develop.go-vip.net/linear.asp.