Power Saving Mode (Psm) - Quectel BC66 Hardware Design

PSM

3.5. Power Saving Mode (PSM)

Based on system performance, the module consumes an ultra-low current (maximally 5μA power
consumption) in PSM. PSM is designed to reduce power consumption of the module and improve battery
life. The following figure shows the power consumption of the module in different modes.
UE inactive time
Figure 3: Module Power Consumption in Different Modes
The procedure for entering PSM is as follows: the module requests to enter PSM in "ATTACH REQUEST"
message during attach/TAU (Tracking Area Update) procedure. Then the network accepts the request
and provides an active time value (T3324) to the module and the mobile reachable timer starts. When the
T3324 timer expires, the module enters PSM for duration of T3412 (periodic TAU timer). Please note that
the module cannot request PSM when it is establishing an emergency attachment or initializing the PDN
(Public Data Network) connection.
When the module is in PSM, it cannot be paged and stops access stratum activities such as cell
reselection, but T3412 is still active.
Either of the following methods can make the module exit from PSM:

After the T3412 timer expires, the module will exit PSM automatically.

Pulling down PSM_EINT (falling edge) will wake the module up from PSM. The timing of waking up
the module from PSM is illustrated below.
BC66_Hardware_Design
In PSM, only the 32kHz RTC is working, and the network is
disconnected. The module will exit from PSM and enter into active
mode when the timer T3412 times out, and it can also be woken up
from PSM by PSM_EINT. For more details, please refer to Chapter 3.5.
Idle
PSM
T3324
T3412
NB-IoT Module Series
BC66 Hardware Design
Idle
TAU
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