Other Parts Discussed in Thread: DRV8320
Oddly when all output drives are low (off) the inverter phases are nearly at full VDS of supply (40v). Our other DC inverters using typical single NFETS have lower VDS leakage <3v. As the high side VDS increased >150vdc that same high FET VDS nears 10v-13v on the phases depending on the 1/2 bridge drive current. The observation was noticed EMF low divider resistor has some effect upon the magnitude of VDS leakage. Obviously the concern is for any static phase voltage >12v being present and more of a human body safety artifact to consider.
1. Has TI ever consider how the resistor divider values raises R1/R2 potentiometer drop across the phase drive output to an unsafe level?
Oddly in our test inverter connected launchXL-x49c reducing R2 top value (470k) to 100k reduced 10v VDS leakage <3v well below 40 VDS.
2. How can the drv8320rs or it's master controller have any affect to reduce the 40v VDS leakage across the NexFETS?
A. Is there an internal register control (drv8320rs) that might lead to excessive IDss driving higher VDS in the NexFETS?
Phase A/B input drive/s held low by MCU during idle time and or high impedance state made no difference to reduce 40 VDS.
Seemingly it is not safe to say since all phases have same leakage they can do no harm. A sweaty repair person might get an unexpected experience should they encounter such leakage. Lets think of the men/women on the front line doing repair jobs perhaps in high summer Tx heat nearing 105°F. Not so much a concern at this early stage of DC motor drives but over time may become more relevant.
3. How does 9k in the R2 (lower EMF divider position) help to reduce VDS leakage across the phase output circuit to much safer level than 40v?
4. Might the PGA amplifiers (F280049c) provide a solution to reduce voltage divider circuit values as to shunt IDss off NexFETS and reduce VDS leakage <40v?
5. Could the drv8320rs Enable pin have some effect on the NexFET idle VDS leakage and or does drv8320rs gate drive controls account for excessive high side VDS?
