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spirilis

FTDI FT230X USB-Serial BoosterPack

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Its interesting to look at the different regulators your boards are using. The Microchip one gives 250mA but at the expense of a higher quiescent current (1.6uA) than the 0.5 - 1 uA the T I one takes for more money and less current (150 uA). I have seen Rob use a different regulator that outputs 800mA, but it drives some less so...

 

Was this in your mind when choosing or did you go with what you guys were already familiar with?

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Somehow I think you could squeeze that board even smaller; I see a buch of vias that are redundant and you might be able to scrape off some caps/resistors or replace them by smaller versions. Ideally the board would be as wide as the USB connector all the way through. Also, when using this one to plug into a USB socket, you must remove the tracks for the mini USB socket, as they'd get shorted out (alternatively have little thinner board and put some insulation on it)

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Richard: I used the MCP1700 because it is low cost, readily available, and provides a good amount of current. It is my favorite small LDO. The LM1117/LD1117 are popular LDO for up to 800 mA.

 

RoadRunner: That board is Open Hardware, so you can hack away at it. A narrow version would be really cool. Maybe also something that would fit in a USB stick plastic case.

 

The extra vias are to reduce resistance in the traces that carry power - it is intentional.

 

When a 2.0 mm board is used, Kapton tape can be used to cover the MiniB connector pad. It is also possible to drill a few vias to disconnect the traces.

 

Family photo of my FTDI boards:

 

post-229-0-01965100-1360135365_thumb.jpg

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Does anyone have an opinion on whether the ferrite bead can be safely omitted from the board? What about the other passives (there are 9 in all!)?

 

I have a cheap breakout board from ebay based on FT232RL that does away with most suggested components (only has two small caps), and it seems to work perfectly fine. I wonder where to draw the line in simplifying the design.

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I think I figured out what I'm going to do with this design.  The run of 20 boards with incorrect decoupling cap setup + using the hideously expensive PTH USB ports is still on my desk sitting unused, until now...

 

Received a run of 6 small boards from OSHpark that adapt the PTH pinout to SMD USB mini-B, which is substantially cheaper.  I think the OSHpark boards add roughly 45 cents to the BOM but with the USB ports coming in just over 50 cents it's still shy of the $2+ for the PTH USB connectors.

The main decoupling cap of interest is on the Vcc5V, and there is room for me to scratch off the soldermask close to the pin and solder my cap there instead.

Got a board all built out, my camera's upstairs so I'll take pics tomorrow or later, but it does show up in Windows as an FTDI with a COM port and I've already reprogrammed the EEPROM to flip-flop the TXD/RXD LEDs.

 

For the store, I'll see if I can solder up as many of these as I can--soldering the USB ports, FTDI chip and supporting caps/resistors, Fuse for the 5V rail, 4.7uF cap for the 5V rail, headers & jumpers for the TXEN/RXEN and leave it at that.  The buyer can source the TPS77333 regulator if they want it providing power to the board and the requisite BOM for those (including headers & jumpers for LDO_EN and LDO_RST).  I have sampled TPS77333 from TI before, so the user may be able to get it for free.  Or they can choose the 3.6V of that LDO.

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