Hello,
Actually, the offset you are referring to (the one set by GDUCSO) is intended to compensate for slight offset changes only - not to create the base offset. In chapter 18.3.2.11 of the Reference manual, you can see the offset voltage can be set from +9mV to -9mV (GDUV5 and V6) or +15mV to -15mV (GDUV4). Integrating an internal full-range voltage reference would be very expensive and would not fit to some usecases anyway. Therefore an external voltage reference should be used to create the base offset.
To create this base offset (e.g. 2.5 V), a voltage divider supplied from 5 V (VDDA) can be used, but it should be of the same impedance as the opamp input resistor network. Or, you can simply reuse what is implemented in our S12ZVM-MINIBRD (see the schematics at https://www.nxp.com/docs/en/user-guide/S12ZVML-MINIBRD_UM.pdf ).
Regarding to your second question, I'm not aware of any simulation model of the opamp provided (maybe somebody else could help on this). From my personal experience, the opamp is designed as an amplifier of these low level signals and I would use it with a gain of approx. 10 to 50, which perfectly fits most of the motor control applications at 12 Volts. I would not recommend to use it as a voltage reference and also not with the gain of 1 (or close to 1).
Best regards,
Matej
