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DAC81401: Voltage sense - use of VSENSEN input

Ian Willats
Prodigy 250 points
Part Number: DAC81401
Other Parts Discussed in Thread: DAC81402,

Tool/software:

Hello,

The data sheet for the DACx1401 suggests that the VSENSEN input should be connected to ground but does not explain whether this required.  Is it possible to lift VSENSEN from ground so that a low-side current sense resistor can be inserted between VSENSEN and ground?  In that case does the device still control VOUT correctly, that's to say maintaining exactly the requested voltage between VSENSEP and VSENSEN, provided VSENSEN is kept well below its absolute maximum of +0.3V (e.g. limited to a maximum of +0.1V)?

While I'm asking: am I right to assume that a high-side current sense resistor can be inserted between VOUT and VSENSEP without any problems, assuming there is enough voltage headroom for the DAC to compensate for it?

I noticed that on the DAC81401EVM, both VSENSEP and VSENSEN are brought out to jumpers which allow them to be disconnected from VOUT and GND respectively, so I am guessing that the DAC will correct its output for small (current sense) voltages in either the high or low side are both supported.

Are there any disadvantages, specifically for the DAC1x401, of using low- vs high-side current sensing?

Thanks,

Ian

  • 0
    TI__Expert 5490 points

    Hi Ian,

    If possible I would request you to go ahead and use the DAC81402 where VSENSEN supports +/-12V offset from GND. 

    Can you please share your design block diagram with DAC81401 where you are trying to implement the low side current sensing and the workings of the same? I can better after that.

    Thanks,
    Sanjay 

  • 0 in reply to Sanjay
    Prodigy 250 points

    Hello Sanjay,

    Thanks for the hint.  Is the DAC81402 not just a dual DAC81401, then?  I see that block diagrams in the respective data sheets do have some differences related to the sense inputs.  Please can you clarify the differences between the two parts, apart from the DAC81402 being dual-channel?

    Being a single-channel part, I'd prefer to use the DAC81401 if possible; I'll post a block diagram shortly to illustrate how I had hoped the low-side current sense might work.

    Ian

  • 0 in reply to Ian Willats
    TI__Expert 5490 points

    Hi Ian,

    I understand your point here. I will check with the team and get back to you in next couple of days. In the meantime, please do send the block diagram.

    Thanks,
    Sanjay