FPGA in a toothbrush?

[NiHaoMike]

https://hackaday.com/2023/05/18/toothbrush-speed-controller-secrets-revealed/
Obviously a very tiny FPGA, buy why that instead of a microcontroller?

[Whales]

Possibly their goal was a custom ASIC and massive manufacture quantity, but perhaps either their quantity changed or they couldn't secure an ASIC contract?  If the product succeeds in the market they might try harder to get an ASIC instead?

[Someone]

Not sure many people would call a GreenPak device an FPGA, they're cheaper than microcontrollers and have a fairly limited count of primitives. Its pretty much what you'd expect for a simple toothbrush where all you need is some power conversion and a timer or two.

[SiliconWizard]

Not sure many people would call a GreenPak device an FPGA, they're cheaper than microcontrollers and have a fairly limited count of primitives. Its pretty much what you'd expect for a simple toothbrush where all you need is some power conversion and a timer or two.

Agreed. It's mixed-signal too, something that a "regular" FPGA *usually* isn't. (Well, it has analog comparators, not much but again most FPGAs do not embed such things.) It's cheap but its simplicity is also a nice feature.

No software => usually fewer problems.

[AK6DN]

Possibly their goal was a custom ASIC and massive manufacture quantity, but perhaps either their quantity changed or they couldn't secure an ASIC contract?  If the product succeeds in the market they might try harder to get an ASIC instead?

I can buy a reel of GreenPAK SLG47513 parts for US$0.46 each.
So spending big bucks to make an ASIC is not a wise choice.
At best you could save about US$0.45 per unit, if you got the ASIC cost down to US$0.01.
Sometimes making an ASIC is the wise thing NOT to do.

[NiHaoMike]

I can buy a reel of GreenPAK SLG47513 parts for US$0.46 each.

Seems relatively expensive compared to low end microcontrollers.

[kleiner Rainer]

There are not many low cost microcontrollers that can operate off a single NiMh cell.

Application note with detailed description:

https://www.renesas.com/us/en/document/apn/cm-360-electric-toothbrush?r=1570446

Greetings,

Rainer

[SiliconWizard]

As I hinted, there are just so many ways to screw up even the firmware of something as mundane as a toothbrush that not using software-controlled solutions at all may justify even paying 4 times the price of the programmable logic component. IMHO.