Optimizing always means sacrifice!?
It turns out that’s only half the truth. Every designer working on battery-powered devices knows the frustration: carefully selecting low-power components, meticulously designing a board, and then realizing—post-production—that sneaky leakage currents are reverse-supplying a chipset. So, how do we avoid these pitfalls?
1️⃣ Wake Up on Interrupt: Minimize active time by using event-driven interrupts. This eliminates energy-draining polling and allows your device to sleep.
2️⃣ Let Others Do the Work for You: Think Smart. Can sensors or radios trigger wake-ups for your system? Many state-of-the-art devices feature functions like wake-up on activity. Combine this with a smart state machine for even better results.
3️⃣ Learn to Read the Datasheet: Datasheets can be tricky. Sleep mode doesn’t always mean the lowest power state. Take the time to study the datasheet and familiarize yourself with the manufacturer’s terminology.
4️⃣ To Cut the Power Line or to Sleep? Weigh the trade-off: Hardware-controlled power gating offers near-zero leakage but slower startup. Deep sleep modes have slightly higher leakage but quicker wake-up. Be aware that some devices don’t save configurations and must be reconfigured on startup. Factor this into your budget.
5️⃣ Understand Your Battery Chemistry: Choosing the right battery for your application can feel like a science. Consider voltage levels, discharge curves, and temperature dependencies for optimal performance.
6️⃣ Support with a Supercapacitor: Small IoT batteries often can’t handle peak currents required for TX. Use a supercapacitor to smooth out transient peaks, but don’t forget about self-discharge.
7️⃣ Protect Polarity Efficiently: Avoid voltage drops by replacing diodes with low-R,DS,on MOSFETs.
8️⃣ Turn Off Unused Peripherals: Unused doesn’t mean inactive. Explicitly disable peripherals like ADCs, UARTs, and SPI interfaces to avoid unintentional power draw.
9️⃣ Measure Current Consumption Properly: Accurate measurements are the foundation of efficient design. Disconnect supercapacitors, debuggers, and COM cables during testing to prevent skewed readings.
🔟 Avoid Rookie Mistakes: Unintendedly supplying peripherals through pin diodes can lead to hidden current paths. Check for current drains through resistor dividers; replace static dividers with dynamically enabled circuits.
1️⃣1️⃣ Don’t Forget Shelf Mode: Devices are often stored long before deployment. Measures like battery tabs or hall sensors can achieve near-zero quiescent current. Alternatively, implement a firmware-based shelf mode.
1️⃣2️⃣ Manage Your Expectations: Start with a simplified battery calculator sheet. Summarize consumptions and duty cycles to estimate your device’s power profile. This helps pinpoint which blocks consume the most and where optimization matters most.
Got any low-power IoT design tips of your own? What are your favorite tools for power profiling?
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