Bq24195 SYS voltage


As I understand, when the battery voltage is above a threshold, BQ24195 connects Vbat to SYS pin. (The schematic says that BQ24195 outputs 3.8V but I can’t find this in the BQ24105 datasheet)

If this is the case, when we connect a fully charged Lipo which is around 4.2V, it will be connected to Ublox Sara module.

Ublox Sara states that maximum input voltage is 4.0V, aren’t we pushing the limits here?

Can you please tell me what I am missing here?

@rifo, the SARA-U2 series has a Vcc range of 3.3v to 4.4v (see page 23 of datasheet) with a typical operating voltage of 3.8v. As such, at 4.2v the SARA is safe. However, the configuration on the Electron is to run the BQ24195 in “boost mode” (OTG pin pulled HIGH, see datasheet section which produces the 3.8v for the SARA module. :wink:

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@peekay123, thanks a lot! I definitely mixed up the typical operating voltage of Sara-U2 series with NB-IOT version.

Due to regulations (I can’t register the imei of sara-U2 on electron to national imei database due to paperwork) I am trying to build an electron by myself.

I soldered the BQ24195 and set it to “boost mode” (OTG pin pulled high, REG01[5:4] = 1,0) but I still see SYS as 4.1V, am I doing something wrong? or does boost mode start working once the battery drops below 3.8V

Note that, since the operating voltage of Sara-U2 is 4.2V, none of this matters but I am asking this out of curiosity.