Sleep Current Arithmetic behind a Five Year Battery Claim
Five-year battery claims require balancing microampere sleep floors, primary cell passivation derating, and protocol airtimes across 43,800 hours.
NB-IoT PSM Energy
Meaning
Discrete quantity of electricity consumed by a narrow-band internet of things module while operating in its power saving mode represents the baseline drain of the connected terminal. Calculating the NB-IoT PSM energy involves measuring the residual current drawn when the radio transceiver and the main microcontroller enter their lowest sleep states while retaining their network registration. This measurement helps designers project battery life without the overhead of renegotiating network attachments upon each wake-up.
Timing Parameter
Active duration is governed by specific timers configured by the network during the connection handshake. The tracking area update timer determines how often the module wakes to inform the cell of its status. Between these updates, the device remains dormant but registered.
Network Registration
Re-attaching to the mobile cell is avoided because the module stores its session keys and network configuration in non-volatile memory during the sleep phase. This continuity eliminates the high-energy cost of a full network search and negotiation when the unit wakes up to transmit fresh sensor readings. If the device remains in this mode for months, the accumulated energy is dominated by the quiescent current of the regulators.
The selection of high-efficiency low-dropout regulators is therefore an important design choice.
Current Profile
Visualizing the power signature on an oscilloscope reveals a prolonged flat baseline interrupted by intermittent peaks during the brief sleep-exit validation routines. Designers measure the area under this curve to isolate the current consumed during the sleep intervals from the active transmission peaks. This measurement determines the limits of the overall power budget for long-term remote monitoring applications.