With the integration of evermore sophisticated logic circuits with power FETs, the search is on for the universal power management device, writes Tamara Schmitz
Power management ICs can deliver increased power, greater efficiency, programmability and higher integration.
At the same time, they are required to reside in smaller packages and enable more sophisticated power management abilities for new applications that require them.
Development of advanced power management technology, such as dramatically lower power requirements and smaller ICs, did not take place overnight. For example, just a half dozen years ago, linear regulators were the choice of many board level designers as they were simple to use and required little to no power design expertise.
Combined with the low cost of linear devices, this simplicity made linear regulators the voltage regulator of choice, while switching regulators were relegated to higher output loads requiring higher efficiency.
There are numerous factors which are make switching regulators more prevalent and relevant for many emerging applications. First, better power dissipation leads to the elimination of special power packages and heat sinks, thereby reducing total complexity and cost.
Second, the power budget management has become extremely important to system designers and, as a result, efficiency has become the main factor in selecting the right devices. Power management is the area in which switching regulators excel, particularly when higher loads are driven.
Third, the cost of switching regulators has decreased over the past few years as rapid improvements in process technologies have allowed higher integration and resulted in smaller die sizes.
Many of today’s switching regulators have PWM controllers, FET drivers and the power FET(s) integrated into a single package.
This is the fourth factor, the higher integration that has allowed a major increase in switching frequencies, which in turn leads to very positive reductions in the size of external inductors and capacitors. The ultimate consequence is a smaller footprint.
A fifth factor: the increase in the “ease of use” factor. With internally-compensated regulators, a designer is no longer required to perform tedious complex calculations to determine the optimal external components to achieve an efficient and stable control loop.
The designer can simply select the input and output capacitors and output inductor from a table based on a set of parameters. With this simplification in implementing switching regulators, the average designer can now take advantage of the higher efficiencies achieved with switching regulators to minimize heat dissipation and maximise power budgets.
Better heat dissipation, higher efficiency, reduced cost, higher integration, higher switching frequency and consequently smaller footprint, as well as ease of use have made switching regulators an attractive alternative to linear regulators.
There remain certain cases in which linear regulators are still the optimal choice, but switching regulators are now the preferred solution among system designers.
Another evolution in power regulation is the adoption of wide input voltage (Vin), multiple output power solutions with highly programmable features.
More and more systems are requiring numerous voltage rails to support the various semiconductors that reside on the board. For example, memory blocks operate at very low voltages to minimise power. Display drivers, on the other hand, must use higher voltages.
Multiple output power controllers can address this demand. For example, the ISL6442 contains two PWM controllers and a linear controller and has an input voltage range of 4.5V to 24V. The switching frequency is programmable from 600kHz to 2.5MHz and features include soft start, voltage monitoring, sequencing, voltage tracking and PGOOD output.
With advances in smaller geometry power semiconductor processes (0.25µm and smaller) and power packaging, power supply chip manufacturers are able to combine high density logic with power FET(s) to create very cost effective, highly integrated and programmable power solutions.
It is now possible to combine power stages that deliver high current (2A - 20A) while accepting a wide Vin (4.5V to 36V) with a digitally programmable controller. This can be a flexible power management design for most system requirements.
What is the end result? A universal, polyphase, wide Vin switching synchronous regulator with highly programmable features including switching frequency, output voltage, variable load, sequencing and control loop parameters.
All we are missing are the voice recognition commands.
Tamara Schmitz works for Intersil
www.intersil.com
