PSM floor value double (8uA instead of 4uA) and eDRX values bigger ( 24uA instead of 19uA) compared to Product specifications using FW 1.1.1

[CommTech]

HI,

We are evaluation the nRF9160 in the devkit and we are trying to obtain the values specified in the nRF9160 Product Specefication v 1.1. After following the different software configuration and HW setups (ex: https://devzone.nordicsemi.com/nordic/cellular-iot-guides/b/hardware-design/posts/measuring-psm-idle-current-on-the-nrf91-dk), we are able to properly activate PSM and eDRX using different values. We are able to achieve pretty slow values but they are all bigger than in the Product Specification :

• PSM floor: 8uA instead of 4uA in the Product Specification
• eDRX cycle for 81.92 eDRX cycle: 25uA instead of 19uA (configured PTW = 1 (2.56sec.) and DRX=2.56)
• Test details:
  • Technology: Cat M1
  • Voltage: 3.7V
  • Current measurement tool: Otii from Quoitech (properly calibrated and achieving the expected low values in other modules that we are evaluating)
  • Modem Firmware: 1.1.1

Do you confirm that modem FW 1.1.1 is able to achieve the values in specification? Any other parameter non stated here that we should take into account.

Here you have some screenshots of the measurements.

eDRX:

PSM

Thanks for the help,

[Heidi-Irene Harvey Sollie]

Hi,

You should set the VDD_IO switch (SW11) to 3V. There is leakage through the RESET pin when VDD_IO is at 1.8 V.

The current consumption during an eDRX cycle is determined by the sleep current for the SIM card, and some cards pull more than others. So the increase is due to the SIM card you're using. 

You can measure the current from the SIM_1V8 pin from the nRF9160 SiP to find this value from the SIM card.

Best regards,

Heidi

[Thomas]

Hi Heidi, 

This leakage current - does it apply only to the devkit? Or is it an issue related to the nrf9160 itself? If not just the dev kit, what is the minimum voltage required for VDD_IO to avoid the excess current?

Kind regards,

Thomas

[Heidi-Irene Harvey Sollie]

Hi! The leakage only applies to the DK, not the nRF9160 SiP itself. 

Best regards,

Heidi