Evaluating Internal RC Oscillator Drift during Deep Power Down
Evaluating internal RC drift requires mapping temperature and voltage sags to expanded radio receive windows that drain battery reserves.
Deep Power Down
Meaning
Low-power states in microcontrollers disable almost all internal circuitry to minimize current consumption during inactive periods. Entering deep power down reduces the power draw of a wireless module to less than one microampere by disconnecting power to the random access memory and the main oscillators. The transition back to the active state requires a full hardware reset or a specific transition on a dedicated wake-up pin.
Current Reduction
The elimination of leakage currents represents the primary advantage of this state. Disconnecting the internal power distribution networks ensures that only the wake-up detection circuit remains biased. This architecture allows the device to remain in place for years on a single button cell.
Wakeup Latency
The recovery from this state takes significantly more time than a recovery from a light sleep mode. Since the system must execute a complete boot sequence, the startup routine consumes a measurable amount of energy. This transient energy consumption can offset the savings from the low-power state if the cycle occurs too frequently.
State Retention
Volatile memory contents are lost when the device enters this low-power configuration. Any network security keys or calibration parameters must be written to non-volatile storage prior to initiating deep power down. Engineers must design the software architecture to reconstruct the system state upon boot.
This initialization step adds a computational overhead that must be factored into the total power budget of the product.