How aggravating is it to pick up an electronic device that you’ve barely used, only to find that the battery is nearly or completely dead? If your device was just on standby or asleep, this may have happened because of a small but crucial specification: quiescent current.
What is quiescent current?
Quiescent is defined as “a state or period of inactivity or dormancy.” Thus, quiescent current, or IQ, is the current drawn by a system in standby mode with light or no load. Quiescent current is commonly confused with shutdown current, which is the current drawn when a device is turned off but the battery is still connected to the system. Nevertheless, both specifications are important in any low battery-consumption design.
Quiescent current applies to most integrated circuit (IC) designs, where amplifiers, boost and buck converters, and low dropout regulators (LDOs) play a role in the amount of quiescent current consumed. In this blog post, I’ll focus on LDOs because of their simple design and ease in calculating power dissipation.