Author Topic: In pursuit of small USB MCU  (Read 1084 times)

0 Members and 1 Guest are viewing this topic.

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
In pursuit of small USB MCU
« on: October 19, 2018, 02:31:03 am »
Is there a small (WLCSP, <=3mm*3mm) USB MCU that has good library support (USB UART w/flow control) and is available in actually manufacturable package (pitch>=0.5mm)?

I came across SAML22, but its 0.4mm package is a huge PITA. PSoC5LP is a good option, but it's way too big, and way to over powered and expensive.

I don't need a ton of pins. Something like EFU8UB10F16-QFN16 is perfect, and it also integrates a voltage regulator, which is much needed, only if it's in WLCSP package.

I'm open to any MCU architecture -- be it 8051, AVR, PIC, MSP430 or any ARM. If he library and compiler is good, I'm even open to 4-bitters.

Any ideas?
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline janekm

  • Supporter
  • ****
  • Posts: 508
  • Country: gb
Re: In pursuit of small USB MCU
« Reply #1 on: October 19, 2018, 03:17:29 am »
Do you have an upper size limit? I did see a few parts in 5x5mm QFN packages which is more or less what you'd get with a 0.5mm BGA...
0.4mm WLCSP is fairly standard now so most modern assembly houses should be able to handle it. Usually for small packages the pinout is designed to put crucial pads close to the edge so you don't need any crazy via specs.
 

Online technix

  • Super Contributor
  • ***
  • Posts: 2782
  • Country: cn
  • From Shanghai With Love
    • My Untitled Blog
Re: In pursuit of small USB MCU
« Reply #2 on: October 19, 2018, 03:48:39 am »
If you are okay with 5x5mm there is STM32F042G4U6/G6U6 in 5mm QFN package. The STM32F042T6Y6 is smaller but that is a 0.4mm WLCSP.

As of library, I have been working HAL-less on STM32 for quite a while. You can fork my DAP42 code as a start point since it has boot code and USB all in place and ready.
 

Offline chickenHeadKnob

  • Frequent Contributor
  • **
  • Posts: 643
  • Country: ca
Re: In pursuit of small USB MCU
« Reply #3 on: October 19, 2018, 04:19:12 am »
Nuvaton makes a USB series (usb 2.0 fullspeed) cortex m0 in qfn 5x5 mm. They have internal high accuracy resonator.
https://www.nuvoton.com/hq/products/microcontrollers/arm-cortex-m0-mcus/nuc120-122-123-220-usb-series/?__locale=en
 

Offline JPortici

  • Super Contributor
  • ***
  • Posts: 2292
  • Country: it
Re: In pursuit of small USB MCU
« Reply #4 on: October 19, 2018, 04:22:16 am »
while we're throwing bigger parts, PIC16LF1455 or ATSAMD21 come in 4x4mm, 0.65mm and 0.5mm pitch QFN
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #5 on: October 19, 2018, 04:31:11 am »
I already have a contender at 3 by 3 mm. Anything larger will not be better than that.

Thanks for the replies, though.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Online technix

  • Super Contributor
  • ***
  • Posts: 2782
  • Country: cn
  • From Shanghai With Love
    • My Untitled Blog
Re: In pursuit of small USB MCU
« Reply #6 on: October 19, 2018, 04:33:12 am »
I already have a contender at 3 by 3 mm. Anything larger will not be better than that.

Thanks for the replies, though.
What might that contender be?
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #7 on: October 19, 2018, 05:12:04 am »
I already have a contender at 3 by 3 mm. Anything larger will not be better than that.

Thanks for the replies, though.
What might that contender be?

EFM8UB10 from SiLabs, it comes in QFN 3*3, QFN 4*4 and SOP24 packages.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline JPortici

  • Super Contributor
  • ***
  • Posts: 2292
  • Country: it
Re: In pursuit of small USB MCU
« Reply #8 on: October 19, 2018, 09:19:48 am »
me shivers.
I know you have access to a reflow over and anything.. but in the past i had to make some prototypes with a radio chip that had  that same package, a gigantic PITA
 

Offline PCB.Wiz

  • Regular Contributor
  • *
  • Posts: 201
  • Country: au
Re: In pursuit of small USB MCU
« Reply #9 on: October 19, 2018, 09:54:18 am »
I already have a contender at 3 by 3 mm. Anything larger will not be better than that.

Thanks for the replies, though.

SiLabs also have EFM32HG series showing in 36-CSP (3.02x2.89), so that's a smaller routed-PCB footprint.
 
The following users thanked this post: blueskull

Offline SiliconWizard

  • Super Contributor
  • ***
  • Posts: 1089
  • Country: fr
Re: In pursuit of small USB MCU
« Reply #10 on: October 19, 2018, 10:35:01 am »
The EFM32 CSP36 has a pitch of 0.4 mm if I'm not mistaken. So that's a pitch blueskull doesn't seem to like much.

Other MCUs with CSP-type packages and 0.4 mm pitch:
The STM32L082 or L052, 2.6x2.9
ATSAML22

NXP KL26 2.37x2.46 (ex: MKL26Z128CAL4R) but you won't like the 0.35 mm pitch.

Finding an MCU supporting USB and coming in a CSP package <= 3x3 and a pitch >= 0.5 mm is no small feat. Can't find any so far.

Yes SiLab's QFN-20 package seems to be the best fit so far, provided that the limited number of IOs is no problem.

Frankly, as for me, I would prefer using a 0.4 mm-pitch BGA/CSP-type package rather than a 0.5 mm-pitch QFN for automated assembly. Any day. At least on the manufacturing point of view. YMMV.
Now if you're hand-assembling, that's another story.

They can be more of a hassle to route on PCB obviously though.
 

Offline wraper

  • Supporter
  • ****
  • Posts: 8442
  • Country: lv
Re: In pursuit of small USB MCU
« Reply #11 on: October 19, 2018, 11:00:24 am »
I don't need a ton of pins. Something like EFU8UB10F16-QFN16 is perfect, and it also integrates a voltage regulator, which is much needed, only if it's in WLCSP package.
You misspelled the part, it's EFM8UB10F16G-C-QFN20. Why would you need WLCSP when this MCU is 3x3mm in size as you asked, 0.5 mm pin pitch  :-//
 

Offline ataradov

  • Super Contributor
  • ***
  • Posts: 4839
  • Country: us
    • Personal site
Re: In pursuit of small USB MCU
« Reply #12 on: October 19, 2018, 01:55:16 pm »
SAM D11 is 2mm x 2.4 mm, but still 0.4 mm pitch. If nothing else, it has fewer pins you need to worry about.
Alex
 
The following users thanked this post: blueskull

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #13 on: October 19, 2018, 02:01:44 pm »
You misspelled the part, it's EFM8UB10F16G-C-QFN20.

Brainfarted.

Why would you need WLCSP when this MCU is 3x3mm in size as you asked, 0.5 mm pin pitch  :-//

QFN needs pad extension. That makes it minimum 3.5mm*3.5mm.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #14 on: October 19, 2018, 02:12:06 pm »
0.4mm is fine, providing I can break out all necessary pins from or through peripheral pins. I can't route traces between pads.
Happy Gecko and SAMD11 look promising, and I'm checking their DS.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #15 on: October 19, 2018, 03:48:19 pm »
Alex,

Can I short PA30 and PA22? I need to bring PA30 out as SWD pin, but I have to bring it out through another ball. Similarly, I need to short GND and PA25.

Of course, PA22 will not be used and will be set to high-Z, so does PA25.

If so, I think this is a wonderful chip -- marginally more expensive than EFM8, and has a much smaller package. The only drawback being the lack of an LDO, whicj is not essentially a bad thing.



Regards,

B.G.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline ataradov

  • Super Contributor
  • ***
  • Posts: 4839
  • Country: us
    • Personal site
Re: In pursuit of small USB MCU
« Reply #16 on: October 19, 2018, 03:52:59 pm »
Can I short PA30 and PA22? I need to bring PA30 out as SWD pin, but I have to bring it out through another ball. Similarly, I need to short GND and PA25.
Not a problem at all. All I/O pins are inputs by default.

I think there is an official VCP implementation, but if you don't like bloat, then I have a small one here https://github.com/ataradov/vcp .

Alex
 
The following users thanked this post: blueskull

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #17 on: October 19, 2018, 03:58:37 pm »
but if you don't like bloat, then I have a small one here https://github.com/ataradov/vcp .

Thanks for the offering. Does it have CTS support? I need to bootload BlackFin+ DSP, and it requires a 3-wire UART with DSP RTS->HOST CTS.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline ataradov

  • Super Contributor
  • ***
  • Posts: 4839
  • Country: us
    • Personal site
Re: In pursuit of small USB MCU
« Reply #18 on: October 19, 2018, 04:06:25 pm »
Thanks for the offering. Does it have CTS support? I need to bootload BlackFin+ DSP, and it requires a 3-wire UART with DSP RTS->HOST CTS.
There are hookups for line status signals, which are used to control a configurable "status" pin. This was done to support a call to the Arduino-style bootloader.

But it is no a full flow control implementation. I frankly got confused by the USB CDC implementation of the line status signals, and gave up on implementing them. I don't think it is hard to add this, I just did not have any motivation to do so.
Alex
 
The following users thanked this post: blueskull

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #19 on: October 19, 2018, 04:46:22 pm »
But it is no a full flow control implementation. I frankly got confused by the USB CDC implementation of the line status signals, and gave up on implementing them. I don't think it is hard to add this, I just did not have any motivation to do so.

Challenge accepted. I'll start form here: http://www.eevblog.com/forum/microcontrollers/usb-cdc-_flow-control_/.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline wraper

  • Supporter
  • ****
  • Posts: 8442
  • Country: lv
Re: In pursuit of small USB MCU
« Reply #20 on: October 19, 2018, 07:31:52 pm »
You misspelled the part, it's EFM8UB10F16G-C-QFN20.

Brainfarted.

Why would you need WLCSP when this MCU is 3x3mm in size as you asked, 0.5 mm pin pitch  :-//
QFN needs pad extension. That makes it minimum 3.5mm*3.5mm.
Considering this package has 4 LGA style pads on the corners, you could just use LGA footprint style for all of them. There is not actual need to expose pads them to outside. Actually I had troubles with this package because when I several times ordered paste stencils and explicitly asked to not modify center pad, fabs reduced center pad area anyway  |O. And then solder got squeezed out from those corner pads. I have doubts if this package should be called QFN to begin with.


« Last Edit: October 19, 2018, 08:35:49 pm by wraper »
 
The following users thanked this post: blueskull

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #21 on: October 20, 2018, 04:06:48 am »
I'll give both them a try on firmware to see which suits better.

Here's a round up so far:

SAMD11: modern, smaller, barely enough pins.
EFM8: included Vbus regulator, built-in resistive divider for Vbus sensing, cheap, more pins, cheaper, lower sleep power, I'm more experienced with it.

Let's see how the firmware goes.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #22 on: October 20, 2018, 03:52:20 pm »
I'll go with the EFM8.

It has a few things that I like:

1. Integrated VREG.
2. Integrated VREGIN scaler for sensing VBUS.
3. Integrated programmable VDD scaler and a versatile comparator with an internal Vref that can wake system up from deep sleep for early brown out detection (very important to me, I need to implement a data buffer that gets dumped to flash upon unexpectedly power off).
4. VCPXpress comes with modem status support. After all, it's presumably the same code running on CP2102N.
5. True 12-bit ADC enables direct current sensor interfacing.

Considering the PCB space for LDO, resistive dividers and ADC input filter caps from using EFM8, I think the overall size should be pretty the same.

Considering this package has 4 LGA style pads on the corners, you could just use LGA footprint style for all of them. There is not actual need to expose pads them to outside. Actually I had troubles with this package because when I several times ordered paste stencils and explicitly asked to not modify center pad, fabs reduced center pad area anyway  |O. And then solder got squeezed out from those corner pads. I have doubts if this package should be called QFN to begin with.

The recommended land pattern is 4mm*4mm. The pads are extended 0.5mm on each direction, which is pretty sick.

Also, it IS a true QFN as it has wettable side walls on the non-corner pads.

Still, I will try to get around with a smaller extension and see what happens.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline wraper

  • Supporter
  • ****
  • Posts: 8442
  • Country: lv
Re: In pursuit of small USB MCU
« Reply #23 on: October 20, 2018, 05:47:16 pm »
Also, it IS a true QFN as it has wettable side walls on the non-corner pads.

Still, I will try to get around with a smaller extension and see what happens.
But one of those corner pads is required to be used as it's a power pin. Therefore when soldering you should treat it more like LGA rather than QFN (must be somewhat elevated above PCB). Otherwise solder might get squeezed out. Just like when those stupid fabs treated it like usual QFN when producing my stencils.  If not extending pads, IMO it should work just like when soldering LGA.
« Last Edit: October 20, 2018, 05:56:53 pm by wraper »
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 10197
  • Country: cn
  • Power Electronics Guy
Re: In pursuit of small USB MCU
« Reply #24 on: October 21, 2018, 01:09:48 am »
If not extending pads, IMO it should work just like when soldering LGA.

I'll try, though I think solder may wick up, but let's see how it works.
Thanks for sharing your experience.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf