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Feature #3313

closed

design simple SFP breakout board

Added by laforge almost 6 years ago. Updated over 5 years ago.

Status:
Resolved
Priority:
Normal
Assignee:
Target version:
-
Start date:
06/03/2018
Due date:
% Done:

100%

Spec Reference:

Description

Let's design a small SFP experimentation board consisting of
  • SFP cage + connector
  • 4x SMA for RD+/RD-/TD+/TD-
  • 2.54mm header for accessing I2C of SFP
  • 2.54mm header with all the misc signals (LOS, etc.)
  • power supply (5V input, DC/DC to 3.3V, 300mA max, filtering as per SFP MSA)

Basically we want the inverse of https://shop.trenz-electronic.de/en/TE0422-02-SFP-2-SMA-Adapter

There seems to be a board close to what we want, but USD 495 is ridiculous for something that has a parts cost of USD 30: https://hitechglobal.us/index.php?route=product/product&path=59_90&product_id=124

The resulting design should be something small which we can easily hand to prototype manufacturers. Staying within 10x10cm might be a good idea, if possible.

In terms of the SFP connector and cage, I would suggest to use

Files

sfp.lbr sfp.lbr 20.6 KB SFP footprint / symbol tnt, 06/05/2018 11:32 AM

Checklist

  • SFP part footprints library
  • schematics
  • board layout

Related issues

Related to Misc Hardware Projects - Support #3524: assemble + test SFP breakout boardResolvedroh09/05/2018

Actions
Precedes Misc Hardware Projects - Feature #3314: design simple SFP experimentation board with LVDS transceiverResolvedmschramm06/04/201806/04/2018

Actions
Actions #1

Updated by laforge almost 6 years ago

  • Precedes Feature #3314: design simple SFP experimentation board with LVDS transceiver added
Actions #2

Updated by tnt almost 6 years ago

I just did a footprint for SFP cage and connectors referenced above. I'll upload it this afternoon (couple of tweaks left :p)

Actions #3

Updated by tnt almost 6 years ago

  • Checklist item SFP part footprints library set to Done
  • File sfp.lbr sfp.lbr added

Added eagle SFP cage and connector. Could use a double check of course :p

Actions #4

Updated by laforge almost 6 years ago

mschramm please let's keep the related eagle library / design files in @osmo-small-hardware.git http://git.osmocom.org/osmo-small-hardware/ and make sure to commit frequently. thanks!

Actions #5

Updated by mschramm almost 6 years ago

  • Status changed from New to In Progress
Actions #6

Updated by mschramm almost 6 years ago

  • Checklist item schematics set to Done
  • Checklist item board layout set to Done
Actions #7

Updated by mschramm almost 6 years ago

  • % Done changed from 0 to 50

A simple PCB has been committed, derived mainly from SFP exoperimenter PCB (see #3313).

Remarks see ticket #3313, some apply here too. - The break in the GND plane under the diff signals of the SFP receptacle is not nice and should be improved on both PCB - if we don't go to a 4-layer PCB (and remain w/ 1.55mm FR4) for a 'closer' GND plane.

Actions #8

Updated by laforge over 5 years ago

13:25 < tnt> Any "real" design using the SFP would be 4 layer, so I guess it's an argument
             to make the experimentation board as close to what a final product would use.

so let's go four-layer. mschramm: please change layer stack-up, add gnd/vcc planes, and adjust trace widths for "usual" four-layer stacking.

Actions #9

Updated by laforge over 5 years ago

let's please also add some form of polarity protection to the DC input. A regular series diode would be the simplest approach, but the TLV1117 requires up to 1.4V drop-out voltage, which makes the budget for 0.7V quite tight. (3.3+1.4=4.7V). Even a shottky diode is unrealistic at that point.

So either we use a different approach for polarity protection, or a different voltage regulator with lower drop-out voltage. Moving away from nominal 5V DC as input voltage is not really a good idea, IMHO.

There are LDOs with built-in reverse polarity protection. However, we cannot use electrolytic caps at the input (C3) in this case. But 10uF at 5V is definitely possible to get as ceramic?

Actions #10

Updated by laforge over 5 years ago

MCP1825ST-3302E would have a maximum drop-out voltage of 0.35V, i.e. allow a series diode. It's readily available and we have used it before (and hence it's in our eagle lib). maybe worth a thought?

Actions #11

Updated by tnt over 5 years ago

SFP+ allows up to 450 mA current to be used by the module.

Actions #12

Updated by tnt over 5 years ago

nm ... I misread the datasheet of that chip, it can do 500 mA ...

Actions #13

Updated by laforge over 5 years ago

Actions #14

Updated by mschramm over 5 years ago

  • Status changed from In Progress to Feedback
  • % Done changed from 50 to 80

PCB revised

  • 4 layer stack
  • LDO is now a MCP1825
  • input protection w/ Schottky series diode and TVS

Some suggestions by tnt still pending (see #3314#note-12), trying to integrate them today.

Actions #15

Updated by mschramm over 5 years ago

  • % Done changed from 80 to 90

added features asked by tnt - see #3314#note-15.

Actions #16

Updated by laforge over 5 years ago

  • Status changed from Feedback to Resolved
  • % Done changed from 90 to 100

Thanks. I extended the default clearance from 0.15mm (was looking quite small in getbv) to 0.25mm, re-ran the DRC and now ordered 10 boards from Seeed.

The clearance change + exported gerber has been committed.

Actions #17

Updated by laforge over 5 years ago

  • Related to Support #3524: assemble + test SFP breakout board added
Actions #18

Updated by tnt over 5 years ago

The boards that I have don't have the 3v3 connected on the bottom pin header.

Eagle schematic and board file look fine, but the gerbers are not ...

Also check on the -experimenter board and on that one, the 3v3 is connected.

Actions #19

Updated by laforge over 5 years ago

tnt wrote:

The boards that I have don't have the 3v3 connected on the bottom pin header.

Yes, I'm sorry, that's indeed a known bug :/

Eagle schematic and board file look fine, but the gerbers are not ...

See "git log", the error was fixed after the gerber/boards were made/tested.

Actions #20

Updated by laforge over 5 years ago

  • Subject changed from design simple SFP experimentation board to design simple SFP breakout board
Actions

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