Forum Post: RE: Help making DRV8412 - 2xDC_motor have simultaneous voltage & current control

Zen,

In voltage mode:
Over these 8 seconds what does the voltage look like (via an oscope).  I suspect that the voltage is likely not around 5V. 

What does the block diagram of your system look like under voltage control?  Level2 * 2?  Or Level4 where voltage is controlled instead of current?  (the first is open loop control of two motors the second is closed loop current control of two motors)


In current mode:
You previously stated that the output will be 24V under current control.  This is not technically correct.  The output voltage will be whatever it needs to be to deliver the amount of current you reference  (ie it will edit the PWM which will vary voltage slightly in order to control current).

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In general, the best (fastest response) way to limit current is to use a comparator and then trip the PWM off when a certain value is reached.  You'd do this via the internal comparators which are at A2, A4, and A6 which unfortunately aren't connected to the most important current signals. 

You could also take a look at the ADC signals to decide when to turn off the PWMs.  Limiting current this way is not ideal but it is usually good enough for voltage.


Thank you,
Brett