INA310A: Extending common mode voltage for legacy DAQ reading a high side shunt.

Hello Eli, 

Thank you for your post. 

I can only comment on the current sense amplifier devices that we offer.

I will need additional details from you: 

• What is the frequency of the shunt current?
• Correct me if I am wrong but you have to use your DAQ with 16V of input range and potentially have a current sense amplifier as an "analog level translator" to bring down the 48V common mode signal with 600mV amplitude signal for the shunt voltage?
• Can you use only the positive rail of your +/-15V setup? If you can then I would suggest using +15V as the supply for the CSA. 
• Is there a reason you are looking at the INA310 with an integrated comparator? I am guessing you may want to have an overcurrent threshold.
• This device will not allow you to have a bidirectional current sensing configuration so we will have to look at other options once I get your full requirements. 

I hope this helps, 

Joe

Joe,

Thanks for the response.  

-It's relatively slow, the application is a programmable DC load, the card scans at around 100Hz, but it's a DC load with set point changes less <10 Hz.

-That's correct, we want to be able to read a high side shunt at 48V common mode voltage with a 16V DAQ.  We have a 600mV 48V common mode differential voltage that we want to become a 600mV 0V (or something < 16V) common mode differential voltage.  

-We can use both the + and - rails of the 15V.  I'd prefer to not have to make a 48V rail form the 5V or +-15V rail if we can't find a solution, but I guess that would be possible.  

- I had to put a part to post to the forum, I couldn't find a CSA with low/no gain, high common mode voltage, and < 15V supply.  Comparator and protection are not needed, just the voltage reading. 

- We only want to read in one direction, bidirectionality is not needed.  

Like you said we're looking for an "analog level translator" with good accuracy to feed to a differential DAQ.  If that involves multiple opamps with something like a CSA to a OPA262 that would work as well.  Thanks.

Hi Eli, 

Thank you for providing those details.

What I am thinking is we use a high input common mode (48V) CSA that operates off of the +15V rail so that the inputs can see the high common mode signal while the output is compatible with your DAQ. 

I also don't know why I was thinking bidirectional so thank you for correcting me. 

So my recommendation is either the INA290 or the INA293.

The benefits for these devices are the high input common mode range (122V) and up to 22V supply which I would recommend using your +15V rail if possible. 

This is a great device if cost is not an issue. 

You will also notice the BW is VERY high. So to make it more suitable for your application, I would recommend low-pass filtering the output. 

It offers the benefit of high accuracy as well. 

Please let me know if this sounds feasible to you. 

Best Regards, 

Joe

Joe, thanks again, that looks good, one question would be the gain.  It looks like the lowest available gain is 20 V/V, that would take my 600mV signal to 12V.  This fits my 0-16V common mode voltage limit, but I'm not sure I can change the DAQ input measurement range from 0-1V to 0-12V.  If I can't, is there another chip I could add to get that 0-12V signal back down to 0-600mV again, while keeping reasonable accuracy?