Global Sources
EE Times-Asia
Stay in touch with EE Times Asia
?
EE Times-Asia > Power/Alternative Energy
?
?
Power/Alternative Energy??

A win-win arrangement, perhaps?

Posted: 16 May 2008 ?? ?Print Version ?Bookmark and Share

Keywords:MCU power supply? low-dropout regulator? digital I/O line?

Schweber: The days of "just give me a clean, stiff supply rail so I can run my MCU" may fade away in the interest of achieving additional system-level power savings.

In many smaller, low-power applications, "they" provide the MCU with a power rail, and the MCU sips that power. (Of course, "they" may be "you," wearing a different hat in the project cycle.)

And while an efficient supply matched to the application is key, it normally provides a fixed voltage. Power saving is done by the MCUs shutting down its internal functional blocks when not needed and going into sleep mode, usually under the direction of the application software.

Larger processors in complex systems do communicate with their supplies, throttling the supply back to save power while the processor goes into a slower clock mode or even to sleep. But MCUs don't have that talk-back, closed-loop option, since their supplies are usually a basic switcher or even a low-dropout regulator.

That's why I was surprised when I saw a new LDO from Texas Instruments that's designed to work with (but not limited to) TI's MPS430 series of ultralow-power MCUs.

Between two output voltages
This LDO can switch between two output voltages, set via a single control line. The MCU in turn uses a simple digital I/O line to tell the LDO which of the two voltage values it wants, depending on its operating mode. The result is that the MCU can direct the supply, and itself, into a lower-power mode. Sounds like a win-win arrangement, and in many ways, it is.

But it does mean that the MCU developer must be aware--early in the software design--of the use of this type of dual-mode LDO, and program that control line as part of the algorithms and code.

It also means that the MCU is tied, for better and for worse, to this particular LDO (those TI folks are clever!) in order to gain the power savings.

The days of "just give me a clean, stiff supply rail so I can run my MCU" may fade away in the interest of achieving additional system-level power savings.

- Bill Schweber
Site Editor, Planet Analog





Article Comments - A win-win arrangement, perhaps?
Comments:??
*? You can enter [0] more charecters.
*Verify code:
?
?
Webinars

Seminars

Visit Asia Webinars to learn about the latest in technology and get practical design tips.

?
?
Back to Top