LMG5200: Power stage for Three-Phase Inverter

luca debs

Part Number: LMG5200
Other Parts Discussed in Thread: LMG2100R044

Tool/software:

Hi!

I should design a three-phase inverter to drive a brushless motor with 7 pole pairs.

I don't have the exact motor data yet, but I know it will be powered with 48V and maximum 5-7A (..tell me if these two data are enough for you or if you need more)

I would like to ask your advice on which power device to use, I have found three:

- LMG5200 (in my opinion perfect for my specifications)

- LMG2100R044 (maybe too high V and I ratings for my specifications, I have an 5-7A motor ... I don't need 35A, right?)

- can you recommend any others devices if there are any and if you think they are more suitable for my specifications? (I have no price problems)

Another thing, for the same specifications, I understand that the LMG5200 (compared to the LMG2100) dissipates more power due to higher Rds,on and Rja... am I wrong?

I ask because heat will be a big problem in the design I have to do and I need to avoid it as much as possible!

5 months ago

0 luca debs 5 months ago

Prodigy 220 points

LMG5200: https://www.ti.com/product/LMG5200

LMG2100R044: https://www.ti.com/product/LMG2100R044

0 Subhransu Satpathy 5 months ago in reply to luca debs

TI__Intellectual 1560 points

Hi Luca,

The overall loss in your system will have both switching and conduction losses.

Given your concern for thermals,

LMG2100R044 (4.4mOhm) seems a good option. But please share the target switching frequency. In case you have a high switching frequency inverter operation, the higher switching loss (due to higher Qoss) of LMG2100R044 may dominate.

Thanks,

Subhransu

0 luca debs 5 months ago in reply to Subhransu Satpathy

Prodigy 220 points

Thank you for your detailed answer.

At the moment I don't know for sure the switching frequency of the Field Oriented Control, I think it will be 30kHz or 60kHz

If I understand correctly:

- at low frequencies dominate the conduction losses given by Rds,on .. so the LMG2100R044 is preferable because Rds,on is much less than that of the LMG5200

- at high frequencies dominate the switching losses given by Qg and Qoss ... so the LMG5200 is preferable because Q is much lower than that of the LMG2100R044

Right?

+1 Subhransu Satpathy 5 months ago in reply to luca debs

TI__Intellectual 1560 points

Yes, this understanding is correct. Since the target switching frequency is not that high, please consider LMG2100R044 for your target application.

Thanks,

Subhransu

0 luca debs 5 months ago in reply to Subhransu Satpathy

Prodigy 220 points

Thank you, very kind.

The fact that my motor draws a maximum of 5-6A while the driver can produce 6 times as much (35A), is that still OK? Or is it oversized?

0 Subhransu Satpathy 5 months ago in reply to luca debs

TI__Intellectual 1560 points

Hi Luca,

Please consider the fact that the RthJA is a variable function of not just the package, but of many other system level characteristics such as the design and layout of the printed circuit board (PCB) on which the part is mounted. Hence it may widely differ from the optimistic value of 29 deg C/W. Hence the exact hearting allowable for you calculated based on your design RthJA best answer your question of how much of an over design is it.

Thanks,

Subhransu

Power management

Power management forum

LMG5200: Power stage for Three-Phase Inverter