i.MX53 voltage monitoring and shutdown

[KarelH]

Hello,

I am working on i.MX53 loco board now, but I would like to make own board based on loco.

I would like to use Li-Ion battery instead of power supply.

What is the best way to monitor the battery voltage in Linux? I want to be able to shutdown the board when the power goes low.

Probably there will be MC34708 as pmic and an external charger.

Thank you,

Karel Havlovic

[JorgeRama_rezRi · Accepted solution]

Hi Karel,

I don't know much about SW and Linux commands, but I can provide a general scope on how to implement your battery monitor:

First of all, the MC34708 shuts down automatically when the voltage at the BP pin (where the battery is normally connected) drops below VBAT_TRKL[1:0] - 100mV. These bits can be programmed by writting to the MC34708 registers via I2C to the following voltages: 2.8, 2.9, 3.0 (default) and 3.1V. For more info, please see section 7.5.3.5 of the datasheet here:

http://cache.freescale.com/files/analog/doc/data_sheet/MC34708.pdf?fsrch=1&sr=2

If these voltages are not suitable for your application, you can implement the monitor manually through MC34708 ADC channel 2. This channel monitors BP, so your software has to keep checking this channel and shut down when it reaches a certain level.

These are the easiest, fastest solutions since they are already implemented in the MC34708. If none of these works for you, you can implement an external monitor to the battery.

I hope this helps!

Best regards.

Jorge.