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PGA 281 Gain Setting - Correct Factors

Michael Staiger
Prodigy 10 points
Other Parts Discussed in Thread: PGA281

Hi, I'm a bit lost with the correct gain setting factor of the PGA281. 

My problem: Is the factor G in meant for the Vop and Von signal or for the difference (Vop - Von). Looking at the datasheet, page 15 says that an 8Vpp input is translated into an 2Vpp signal at either Vop and Von. The difference of Vop-Von is explained in the diagram as 4Vpp. In the parts symbol at the drawing Gain G is defined as 1/4. Besides the issue that I would expect the difference signal symmetrical to 0V and not VOCM, everything seems consistent. 

Only trouble I have, that the corresponding TINA-Model behaves differently: 

I changed in the file "High-Side Current Sensing"  VG1 to a sinus source with 4V amplitude.Then I changed the G-bits to 00001 to set G=0.25. Results from simulation show:

Input Voltage 8Vpp, but output voltage at  Vop and Von results in 1 Vpp and difference (Vop-Von) as 2Vpp. That differs from the example in the datasheet by the factor of two.

So I'm unsure, which result is correct, datasheet page 15 or TiNA simulation?

Best regards 

Michael

  • 0
    TI__Genius 12335 points

    Michael,

    Thank you for bringing this to our attention, the simulation is the correct representation of the PGA281's functionality. The gain measurement reflects the differential output voltage divided by the differential input voltage. We will work to correct the figure in the datasheet to accurately reflect this.