NRF9160 Firmware modem & Battery

[Alskandar]

Hi,

I encounter a problem, in my opinion, related to the modem firmware (or model B0 and B1).

My program connects to the LTE-M network and sends data from a sensor.

I use the Icarus board from Actinius and test the following configurations:

• Version B0 (old board, v 1.4) + Firmware 1.2.3 + SDK 1.9 -> Works on USB and Battery
• Version B0 (old board, v 1.4) + Firmware 1.3.2 + SDK 2.1 -> Failed (but it's normal, firmware not aligned)
• Version B1 (v2) + Firmware 1.3.2 + SDK 1.9 -> Works on USB but Failed on Battery
• Version B1 (v2) + Firmware 1.3.2 + SDK 2.1 -> Works on USB but Failed on Battery

Can't run the new B1 Version on battery (but works on USB). I don't understand why.

Battery -> LS17500 3,6V from Saft (so ok).

Does somebody have an idea ?
Does the modem need more power ??

Thanks

[ketiljo]

The battery isn't able to supply the needed peak current to the modem. 

From the battery datasheet: 

And the nRF9160 product specification: https://infocenter.nordicsemi.com/topic/ps_nrf9160/_tmp/alta.nRF9160/autodita/CURRENT/parameters.id_current_modem.html

If you scope the battery voltage, you will see that drops below the reset threshold when the modem is active. The TX peak current depends on the distance to the cell tower. When you're at the edge of the cell, the output power will be at it's highest. 

[Alskandar]

Thanks, your answer concerns the B1 (rev2) model ?
Or, is it due to a specific firmware ?

With the B0 model, i have no problem with battery.

[ketiljo]

This will be the case on all revisions. It can be a coincidence that it works on one of the revisions only depending on what cell tower it connects to. You need to use a better battery for stable system.

[Alskandar]

When you say:

ketiljo said:

If you scope the battery voltage, you will see that drops below the reset threshold when the modem is active. The TX peak current depends on the distance to the cell tower. When you're at the edge of the cell, the output power will be at it's highest. 

Is it in reference to this line ?

IRMC_23DBM

Uplink 180 kbit/s, Pout 23 dBm, RMC settings as per 3GPP TS 36.521-1 Annex A.2

100

105

115

115

mA

or

ITX_23DBM

TX subframe, Pout 23 dBm

255

275

295

290

mA

In the worst case, i need to find a battery who accept max current greater than 435mA (Cat M1), right ?

[ketiljo]

Yes, look at the peak currents at the bottom of this table: https://infocenter.nordicsemi.com/topic/ps_nrf9160/_tmp/alta.nRF9160/autodita/CURRENT/parameters.id_current_modem.html

> 300 mA is to be expected. 

[Alskandar]

Thank you, it works !