DRV8876 - Anyone use the current measuring feature?

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Joined Jul 12, 2016
TI provides a spice model for this motor controller part which I am running in LTspice. The input controls and power outputs seem to work ok. The model explicitly says it does not support the voltage boost circuit which creates the voltage to drive the internal high side nFETs. It also does not model the power consumption. It does claim to model the current measurement output IPROPI which is a current mirror output at 1/1000 to the current through the low side FETs.

The data sheet talks about the measurement reflecting whichever low side FET is turned on as long as the current is flowing into the chip, as they put it, drain to source. When both low side FETs are on if only one is conducting current into the chip the measurement is supposed to be of that one pin otherwise it sums the current of both FETs. The trouble is in simulation this seems to work for a few periods of time in brake mode when both FETs are conducting drain to source, but otherwise the IPROPI current appears to be rather random not being the sum or difference or equal to either of the two low side output currents.

I'm hoping this is just a simulation bug. But if this feature doesn't work in the chip, constructing a board will be a total waste of time. Support is trying to help, but they start with all manner of advice that is not very relevant. They now have my simulation files. Maybe I'm using the chip wrong in some way, but it seems pretty simple.

I'm wondering if anyone has used this device and can tell me if the current measurement works in the chip.