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KA , 05-10-2025, 05:53 AM

Hi everyone!

I’m designing an ESC to drive a BLDC motor and came across a schematic using MOSFETs in a half-bridge configuration. Since this is my first time working with high-power MOSFETs, I’d love your input on a few things:

1) **MOSFET Selection** – What’s a good thumb rule for shortlisting N-Channel MOSFETs based on voltage and current ratings of the load before diving into SOA curves? My setup: 6S (25.2V) battery, 50A continuous load.
2) **BSC016N06NS Suitability** – Is this MOSFET (https://www.infineon.com/dgdl/Infineon-BSC016N06NS-DataSheet-v02_06-EN.pdf?fileId=db3a3043353fdc160135532b353c483c) a good fit for 6S (25.2V) and 50A continuous current? From the SOA chart, 50A at 0.16V implies ~8W dissipation - is that correct? The datasheet lists 164W (Tc=25°C) and 3W (Ta=25°C) for power dissipation. How do I design the additional heat sinking?
3) **Thermal Estimation** – The thermal characteristics table includes multiple factors. Which one should I use to estimate temperature rise during continuous operation?
4) **SOA at Higher Temperatures** – The SOA is specified at Tc=25°C. How does it degrade at higher operating temps?
5) **PCB Design Considerations** – What trace widths, heatsinking, or layout practices are critical for reliability? I plan to use a 6-layer PCB with 2 or 3 oz copper.

Thanks in advance for your help!

QDrives , 05-10-2025, 03:16 PM

SOA is not interesting for BLDC motor control as you be doing hard switching and driving into saturation.
60Vds is good, but you may consider a lower voltage as your current is high.
1.6mΩ Rdson is high for 50A continues. You dissipate about 4W. With the datasheet cooling method, the temperature rise would be 200°C, way above junction limits.
Not mosfet selection, but 5V is to low voltage for the DRV8300.
Other considerations:
- Qg (total gate charge)
- Thermal conduction (both top and bottom)
- Vth (if you want to stay with 5V).

For trace widths, it depends on the temperature rise you allow. With 3oz copper, 20°C temperature rise, 0.2mm above plane -- you need about 30mm wide traces.

Sniper2 , 05-10-2025, 06:51 PM

well uou could use multiple in paralel

Sniper2 , 05-10-2025, 06:52 PM

Also is 50A at max power at max load? asking since u sort of need to compensate for battery discharge in ESC controll

Sniper2 , 05-10-2025, 07:14 PM

also wouldnt it be better to use higher voltage and less currrent? if u can change that

QDrives , 05-10-2025, 10:13 PM

Perhaps he needs to get the drone high fast before the batteries explode?

KA , 05-11-2025, 07:27 AM

@Sniper2 Yes, for e.g. a motor rated at 50A max continuous current (180s), at full throttle.
I'm trying to keep the BOM and board size small, so not intending to use FETs in parallel.

KA , 05-11-2025, 07:30 AM

I haven't finalized the mosfet. BSC016N06NS was something I shortlisted based on low Rdson. What do you suggest for *"higher voltage and less currrent"*?

Sniper2 , 05-11-2025, 07:49 AM

https://eur.vevor.com/brushless-dc-motor-c_11227/vevor-1800w-electric-brushless-dc-motor-48v-4500rpm-motor-for-e-bike-dirt-bike-p_010506884872?lang=en¤cy=eur&adp=gmc&country=RO&utm_source=google&utm_medium=cpc&utm_id=17533906258&ad_group=144696839944&ad_id=604868505519&utm_term=&gad_source=1&gad_campaignid=17533906258&gclid=Cj0KCQjwlYHBBhD9ARIsALRu09qAX6WZyO_LkmgLwtiCvXCNLv8flV5pupGktNRMW1FdZq1bERlioAEaAjl8EALw_wcB

like that 48 V motor

Sniper2 , 05-11-2025, 07:49 AM

your motor now is 24V

Sniper2 , 05-11-2025, 07:49 AM

if you double voltage u halve current

Sniper2 , 05-11-2025, 07:50 AM

but not sure what other specs you need and if there are motors for 48V with those specs

Sniper2 , 05-11-2025, 07:50 AM

maybe but that iis still 1-1.2kW continuous in his specs

Sniper2 , 05-11-2025, 07:52 AM

hmm that is way to long of a period where u can say u can tank the heat and cool later

Sniper2 , 05-11-2025, 07:54 AM

btw dont expect to find much under 1mOHM since the packet is at that point most of the RDSon

Sniper2 , 05-11-2025, 07:54 AM

maybe with a larger packet

KA , 05-11-2025, 07:55 AM

Ah, I see. This for a drone as @QDrives guessed it. 12S batteries are heavier than 6S. So the 6S battery is the constraint for the design.

Sniper2 , 05-11-2025, 07:56 AM

well for the same capacity it is heavier , but for same energy it should be the same

Sniper2 , 05-11-2025, 07:56 AM

if u need 6s ok

Sniper2 , 05-11-2025, 07:57 AM

but then you sort of need to go with paralel fets or something to cool the fets

Sniper2 , 05-11-2025, 07:57 AM

or simply FETs in a huge pack

KA , 05-11-2025, 08:05 AM

So taking the BSC016N06NS as an example — if I add 2 FETs in parallel, the power dissipation drops to 2W per FET, and the temperature rise comes down to around 100°C, right? Also, adding an aluminum heatsink on top should help dissipate the heat better?

Sniper2 , 05-11-2025, 08:13 AM

yes and no

Sniper2 , 05-11-2025, 08:13 AM

50x50x1.6 = 4W

Sniper2 , 05-11-2025, 08:14 AM

25x25x0.8 = 0.5W per fet

Sniper2 , 05-11-2025, 08:14 AM

so 1W in total

Sniper2 , 05-11-2025, 06:37 PM

@KA i think i convinced u LOL