Hello,

I'm in need to measure current draw on 5 lines. My idea was to have power coming from LDO trough current sensor (ina226) to 1:8 power switch. 1:8 analog switches seem to be scares. 3 lines are typically up to 0.25A, 2 up to 0.6A. Power is coming from 3.95V LDO.
Currently I'm thinking about using BD8LB600FS switch.

Is there a better way to do this? Without having 5 current sensors ofcourse.

 

Is the purpose of the 1:8 switch to select one load at a time for measurement?
SG

 

@sghioto Yes, one at a time.

 

Yes, one at a time.

Then you would only need one INA226 and one current shunt,correct?
SG

 

Yes, current sensor before Input to switch.

 

Seems to me you have this figured out OK, without seeing a full schematic?
SG

 

Thank you. Working on schematic now. New to EE. Figured I will ask if there other ways. Eventually I want to make a version measuring 60 lines.
Essentially right now is LDO > Current Sense > Switch to 7 lines.

 

Working on schematic now.

Sounds good. Post the schematic and I'm sure there will be more input from other members here.
SG

 

Will this kind of resistance pose a problem?

 

Hi goextreme, to clarify, your 5 lines each have a sense resistor in them? So you just need to switch the one of the sense terminals of the INA226?
Your idea to use an analog switch sounds ok, and you should be able to find quite a variety around, like the MAX328.

 

Attaching schematic. I've put 2:8 L9825 switch since I might use 2 different voltage for 2 lines.

@DickCappels I'm not sure. This is to measure leaks on the charging circuit.

 

Hi GoExtreme, you are unlikely to find an analog switch that are able to cope with the current you are using. Your best bet would be to use either your existing high side arrangement, and some P-Mosfets that you switch (with some sort of multiplexer). Or you use low side sensing and use N-Mosfets and multiplexing. The latter would be more simple.

 

When you get to the bigger design I can get routed on 1 chip a 50 channel mux with 16 bit
A/D and Vref ( you should not need IA). The A/D is 20 bit but I would stick with 16 bit. That
would give you a res of ~ 15 uV, a range to 1 V, and its CMR is 100 mV outside the rails
on part. This part has arm core.

One possible approach is to do one high end chip with 50 channels, a low end controlled
by high end with the other 10 or more channels.

Regards, Dana.