Embedded Systems & Firmware

A sensor device runs at 10 mA for 1% of the time and sleeps at 10 µA for the remaining 99%. What is the closest average current?

  1. AAbout 0.11 mA
  2. BAbout 5 mA
  3. CAbout 10 µA
Show answer and explanation

Answer: A. About 0.11 mA

The average current is the sum of each current multiplied by its fraction of time: 10 mA × 0.01 = 0.1 mA and 10 µA × 0.99 ≈ 0.0099 mA, about 0.11 mA in total. As here, even a brief active time often dominates the average, so finishing work quickly to sleep sooner and minimizing sleep current both extend battery life.

  • A. Correct. 0.1 mA plus about 0.01 mA.
  • B. That averages without weighting by time.
  • C. The active current contributes significantly.
Practice this topic Back to topic

More Embedded Systems & Firmware questions

  1. Why does firmware on small microcontrollers often avoid dynamic memory allocation such as malloc?
  2. On a small microcontroller without an MMU, what should be kept in mind about excessive stack use?
  3. A 12-bit A/D converter with a 3.3 V reference reads a value of 2048. What is the closest input voltage?
  4. When a microcontroller captures many A/D conversion results at regular intervals, what is the advantage of using DMA?
  5. When representing peripheral registers with C bit-field structs, what needs care?