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DRV8301: reduce amplification of internal OP?

gerd.mitlaender
Prodigy 110 points
Other Parts Discussed in Thread: DRV8301

Hi...

Is it possible to reduce the internal amplification of the DRV8301 by placing additional serial resistors in front of SN and SP? According to DRV8301 pdf (SLOS719, page 13) the op amplification is set by a 5k serial resistor and 50k/100k/200k/400k in feedback loop resulting in 10x/20x/40x/80x.

Adding additional resistors in front of SN/SP of

a) e.g. 5k would lower the resulting amplification to 5x/10x/20x/80x.

b) e.g. 15k would lower the resulting amplification to 2.5x/5x/7.5x/10x.

Is that possible?

Gerd

  • 0
    TI__Guru 55615 points

    Gerd,

    Theoretically, this would be possible, but you can't rely on that 5k resistor actually being 5k over process and temperature.  We layout the device so that the resistance will track over process and temperature as much as possible.  In other words, the 50k in the feedback can change +/-30% and the input will shift a similar +/-30%.  This keeps the gain within the tolerances we specify in the datasheet over process. 

    That is the risk of putting a series resistor external that doesn't account for the shift in the input resistance.