TAN004 – Power-off Recommendations for SARA R410M-Equipped Devices

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Originally published at: Technical advisory for SARA-R410M cellular devices - Particle Changelog

TAN004 – Power-off Recommendations for SARA R410M-Equipped Devices has been published with guidance for safely powering down devices including the Boron LTE (BRN402, BRN404), B Series B402 and B404, E Series E402 and E404, and Electron LTE ELC402 and ELC404.

 

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Thank you for publishing this. Adding a battery is not possible everywhere due to the limited temperature range and increased regulatory requirements.

You are stating for the power supply of the B402:

The recommended input voltage range on this pin is between 3.6V to 4.2V DC. Make sure that the supply can handle currents of at least 2 A.

A supercapacitor being able to supply 2 A for 30s with a voltage drop of 0.6V would have a capacity of about 100F, which is quite big. The modem will probably not need 2A in this 30s, but how much energy does it need?

  • Can you please specify the requirements (max. current, energy) of the backup power source?
  • What about the Quectel modem on the B524? Can you confirm that this modem is not affected by this issue?

Thank you!

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This issue is specific to the u-blox SARA-R410M modem. It is not known to affect Quectel modems or other u-blox modems, however graceful shutdown is always recommended.

The exact amount of power is hard to quantify. It is less than 2A for 30 seconds because the modem will likely be in the process of shutting down and not transmitting at full power. However, the exact power is hard to determine because it probably will depend on when you initiate the power down. Since it’s an R410, it will be less than 500 mA, and probably even less than that.

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