ULP stands for ultra-low power and although both the phrase and the acronym are in fairly common use, a clear definition has been more elusive.
Nordic Semiconductor recently offered its version of a definition, which seems pretty useful to me.
It all starts with a practical distinction based on batteries. Electronic systems that run for a days or weeks on a AA or AAA battery are defined as low-power systems. If you can run a system on a single coin cell (the CR 2032) for a year or more, then you are in ULP territory.
Nordic, by the way, is (as one might guess) very much into ULP. Its wireless transceiver chips were targeted for Nokia's short-lived WiBree initiative. When WiBree was rolled into the Bluetooth SIG as its ULP technology, Nordic came along for the ride, although the role of its technology in a standard-based environment is not entirely certain.
The idea of running a system on a coin cell for a year has practical appeal. Nordic could have chosen another coin cell as its benchmark but that's pretty much of a quibble. Applications would include sensors worn on the body that communicate with a small collection device such as a watch or mobile phone.
The numbers behind Nordic's version of UPL are also pretty simple: A peak current of 20 mA and an average current of 2 μA. Clearly, you can't be running at 20mA for very long if you intend to average 2 μA over the course of a yearand that's where both semiconductor technology and protocols come in.
I'll be writing more about this in the future but if you have any comments, you can post them by clicking the "log in or register here" link below.
If you'd like to look a little deeper into Nordic's technology, visit www.nordicsemi.com.