Subscriber Identity Module (SIM) cards can have a big impact on the average current consumption on your designs.
Historically, SIM cards were designed for devices with big batteries and current consumption optimization was typically not considered during development. However, in ultra-low power devices like nRF9160, we often see SIM idle currents that are 10 times larger than the Power Saving Mode (PSM) floor current of nRF9160.
Current measurements are easy with the accessible pins on the nRF9160 DK. We recommend that you ask your SIM card provider about this and gather how much current their SIM card is consuming in clock stop mode.
Our advanced modem automatically optimizes the power consumption of the SIM card, but you can further improve this if the SIM card has the UICC suspend-resume feature enabled (specified in 3GPP TS 31.102 chapter 5.1.11). You can request this when ordering SIM cards to ensure that the SIM card does not use unnecessary current when not in use.