Hey all,
I'm in the process of trying to use the DRV8301 as a FET driver for a 3-phase step-up (boost) converter, which to date has been met with only moderate success.
Below is a part of the schematic for the custom board I'm working on. The DRV8301 is more or less used as designed, the only major difference is the addition of an external charge pump that ensures that the bootstrap capacitors (C505, C506, C507) remain charged in the presence of a DC bias on the SH_n nodes. This is more or less what is described in this thread; http://e2e.ti.com/support/applications/motor_drivers/f/38/t/285753.aspx and seemed (?) to work at the time.
Note; R504, R506, R507 are changed to 100k and R512 is changed to 1R.
I've made sure to initialize the DRV8301 in a way similar to what was done in the aforementioned thread, below is an example of my start-up routine for the DRV8301;
And a more detailed view here;
First off, I write 0x16C0 (1.7A drive current, No reset, Normal (6-wire) PWM mode, OCMODE for current limit, and a current limit of 1.491V), which I verify with a 0x9000. This returns 0x16C0 so I'm relatively confident the values were parsed correctly. Similarly, I write 0x1800 (OCTW mode both, internal gain of 10, calibration disabled, and OC off-time normal) and verify in the same way. Afterwards, I send a few short pulses to the INL_x inputs, and finally apply the desired duty cycle.
My main problem at the moment is that phase B does not start up at all, regardless of the input there is no output on neither the high side nor low side gate. At first I had not mounted the additional charge-pump and I experienced behaviour similar to that in the link above, and couldn't start up at voltages above 13V or so. This threshold varied slightly from phase to phase. After adding the charge pump the bootstrap capacitors are consistently held at around 12V (both in idle and when active) by the external charge pump section and phases A and C start up reliably, however phase B does not.
(For reference, the three phases are driven 120° out of phase, currently at 20kHz, using the IRFS3006-7PPbF FET (Qg_tot typ 200nC, max 300nC)).
Does anyone have any idea as to how I can get going? Any help would be very appreciated; I've spent far too much time on this as it is already...
//Jonathan