下载
Maxim > Design Support > Technical Documents > Application Notes > Battery Management > APP 4427
Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 4427
Maxim > Design Support > Technical Documents > Application Notes > General Engineering Topics > APP 4427
Keywords: standby power, energy efficient, budget power, microampere, computers, notebook, set-top
box, battery life, remote air conditioning, environmental impact, voltage reference, quiescent, bandgap
APPLICATION NOTE 4427
Demonstrating Green Technology with Apples,
Oranges, Lemons, and Limes
By: Bill Laumeister, Strategic Applications Engineer
Oct 10, 2011
Abstract: Green initiatives bring home the issue of wasting standby power. Through reducing their usage
of standby power, U.S. households can save an average of $100 per year.¹ Battery life in portable
devices is important, but this application note shows that power-saving appliances in our homes are also
critical to reduce environmental waste. Maxim is taking the lead in energy-efficient integrated circuits, and
this document lists examples of Maxim parts used to reduce power in appliances, computers, and set-
top boxes.
Jim Henson's creation, Kermit the Frog says, "It's not easy being green." We concur that saving energy
is difficult, but very necessary. Smart circuit designers and progressive companies are meeting
consumer's expectations in this aspect. And the smallest details are critical: power efficiency is one
measured in microamperes (µAs), one-millionth of an ampere. For comparison, a 60W incandescent light
bulb draws 0.5A. That is 500,000µA.
Why is it necessary to measure so precisely? Because it is the sum of all currents that count and like
any budget, one must reduce every cost, no matter how small. Obviously in a battery-powered device,
customers are sensitive about battery life. Not so obviously, plug-in appliances also have a cost
associated with just being plugged in. When a device is "off", but displays a power indicator while waiting
for a remote command, button, or timer, it is consuming standby power.
What is the cost of standby power? That 60W bulb can cost $14.65* a month if it runs 24/7. An
appliance that draws 1W in standby power can cost $0.25 without doing any practical work. Walk around
a typical home and count the appliances, TVs, radios, stereos, computers, garage-door openers,
microwave ovens, washing machines, dryers, forced air heaters, and lawn sprinklers. Then add the
battery chargers. You can easily have 20 devices on standby power, and most draw more than just 1W.
That is the good news. The bad news is that a cable TV box can draw 80W while in operation and 79W
while in standby (costing $19.53 and $19.30, respectively). A satellite DVR box can consume 120W while
in operation or standby, so just add $29.30 to your monthly subscription rate.
This is relevant not only as a monthly cost; as a citizen of Earth, we must be conscious of our
environmental impact. As circuit designers, we can choose carefully, and thankfully low-energy parts are
Page 1 of 6
