DRV8305 Reference Design Questions

Hi Asifjahmed,

Please refer to the following answer.
1) Just because C2000 MCU need more than 50mA current which is beyond the output ability of DRV8305.
2) Vds is the sensing voltage from MOS's D to S for over current protection. So not quite understand your question about PVDD and Vds. In this design we need to make sure the overall voltage of the PVDD bus <30V. TPD4E05U06 is to do ESD protection as well as peak noise voltage to DRV8305. It is not a must be component but it will help to make the design more robust in all conditions.

I will inform our designer of this to make any comments to you question.

Best regards,

Hi Asif,

1). Wilson is correct. The DRV8305 regulator is not big enough to supply a C2000. It can power many lower end MCUs though. We have another reference design that highlights this. http://www.ti.com/tool/tida-00645

2) TIDA-00643 is design to run on 3s and 4s LiPo batteries typically used in ESC design. This gives you the margin with 30 V. We rate the design to 30 V since it is fully functional to 30 V. You are correct thought, at 30 V their would be no margin with the MOSFET breakdown spec.

On reference design we often try to highlight additional TI components. The TVS is giving some additional protection to the MCU against ESD strikes on the motor and supply lines. A common path for ESD is through connectors to the PCB.

 

Thanks much Wilson and Nick!

That is a real bummer about the DRV83053 not having enough juice to supply the TMS320F28027F :-( I am unable to find a spec on the current requirements of the device?

And that makes sense on the TVs protection. Seems like a sound design consideration!

Best,

-asifjahmed

Current consumption by the MCU depends heavily on the operating mode and what peripherals are active.

http://www.ti.com/lit/ds/symlink/tms320f28027f.pdf

Section 6.4 (page 81) of the datasheet is where they start describing.

Thanks, Nick.

So clearly I will need a switching regulator and supporting components in my design (the 50 mA from the DRV83053 being insufficient was an oversight on my part). Honestly, as convenient as it would be for me to use the same circuit in your reference designs (LMR16006), the selected components are all on the pricier side.

As an alternative, I have found the Rohm BD9G101G (http://www.mouser.com/pdfdocs/bd9g101ge-2.PDF). This seems to be a comparable IC, but I have one primary concern.

In the data sheet, it says that the minimum output voltage is based on the minimum on pulse, which is around 100nsec. According to my calculations, this means that I cannot achieve 3.3 V if the input voltage is > 22 V. However, in one of their application notes (http://rohmfs.rohm.com/en/products/databook/applinote/ic/power/switching_regulator/bd9g101g_brd_appli-e.pdf), they have a reference circuit with 3.3 V out and 24 - 40 V in. Can someone please help me understand this better?

Here are my design specs:

Input voltage:             6.6 - 33.6 V
Output voltage:           3.3 V
Output current (RMS): 250 mA



Apologies in advance if I didn't provide all the necessary info. Any help is much appreciated!

Hi Asif,

I cannot comment on non-TI devices.