MCF8316A: Maximum motor power

joe van Niekerk

Part Number: MCF8316A

We have a 24 V motor system that we need to drive at 6 A. The part specs seem to indicate this is possible, but in the forums I found mention of a 70 W input power limit. This is so far from the 35 V, 8 A spec.

Why is this not called out in the datasheet. Is it an errata? Are there any workarounds? Doesn't seem like there is a thermal reason for this limit.

over 2 years ago

0 joe van Niekerk over 2 years ago

Prodigy 50 points

Ok, found the calculator and it seems to make sense.

0 Andrew Liu over 2 years ago

TI__Mastermind 18981 points

Hi Joe,

Thanks for posting to e2e motor drivers forum - please see my answer below:

In an int-FET device such as MCF8316A (in which the MOSFET power stage is integrated to be within the IC packaging), motor phase current is conducting across the Rdson of the FETs, producing heat as a result of power dissipation). The reasoning behind the Power wattage guidelines is indeed thermals (see below).

Around 70-80 Watts is where we draw the line on device power dissipation exceeding the thermal capabilities of today's Silicon and IC packaging technology. Too much temperature will cause the thermal shutdown to trigger or induce damage.
Your specific application at 24V and 6A results in a combination outside the 70W threshold, but a different operating condition such as 24V, 2A or 12V, 6A would be more in-line with expectations for this device. Each current/voltage has its own limitations, but there is also the combined limitation of wattage

In the event that an integrated-FET's wattage limitation is not acceptable, we have other external-FET solutions within the TI BLDC driver portfolio

Further explanation of the power/thermal considerations in integrated-FET devices:

https://training.ti.com/thermal-considerations-integrated-mosfet-drivers?context=1139747-1138777-1139744-1150020

Tools for evaluating power/thermals in this device:

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1078268/faq-bldc-integrated-mosfet-thermal-calculator?tisearch=e2e-sitesearch&keymatch=faq%3Atrue

Best Regards,
Andrew

0 Andrew Liu over 2 years ago in reply to joe van Niekerk

TI__Mastermind 18981 points

Hi Joe,

Awesome!

Glad you found the answer you wanted - I was typing out the reply below, which may still have some other info useful to you (including the calculator tool).

Hope you have a nice day, and do let us know if you need further support. Thanks!

Best Regards,
Andrew

0 joe van Niekerk over 2 years ago in reply to Andrew Liu

Prodigy 50 points

Thanks, I'm sure your reply will help others as well.

0 joe van Niekerk over 2 years ago in reply to Andrew Liu

Prodigy 50 points

Are there any current or planned external FET solutions that are microcontrollerless like the MCF8316A? We currently have a microcontroller based FOC solution that can do higher power.

0 Brian Dang over 2 years ago

Genius 5040 points

joe van Niekerk said:
We have a 24 V motor system that we need to drive at 6 A.

I don't think you want to apply the full 24v at 6A to the motor at stalled condition, and so the power is not 24v x 6A. Based on the motor wiring resistance, 6A current might only need 8V across the motor.

So motor power = (voltage cross motor - BEMF)x motor current.

Brian

0 Andrew Liu over 2 years ago in reply to joe van Niekerk

TI__Mastermind 18981 points

Hi Joe,

This is definitely an interest area for organization, so we appreciate the feedback showing interest from customers such as yourself.

I can't speak too much publicly on our ongoing developments or upcoming roadmap today, but please stay tuned on our TI motor drivers BLDC product page for latest updates on product releases and promotion: https://www.ti.com/motor-drivers/brushless-dc-bldc-drivers/overview.html

A device like you are considering would typically fall under the 'MCx' product family classification for integrated-control, so the part will have MCF (FOC) or MCT (Trap) in its name.

Best Regards,
Andrew

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MCF8316A: Maximum motor power