ABSIS ALE Power Regulation

[jrsteensen]

Description

PCB

MC RAW PIN is now NC
Added MIC5219 regulator (and supporting components to include 500mA polyfuse) to supply VCC pin of MC (includes a NC solder jumper bypass of regulator.)
Updated version to 4.0.0
Added several jumper pads to allow the user to customize the functionality of the power circuit. (See note 4 on schematic.)

4) POWER CONFIGURATION:
1) WHEN USING CLONE OR SPARKFUN PRO-MICRO, SOLDER JP1/JP2, AND
LEAVE JP3 OPEN.
2) WHEN USING OH PRO-MICRO OR KNOWN GOOD PRO-MICRO (HAVING BEEN
TESTED FOR GOOD VOLTAGE REGULATOR AND/OR NOT CONTAINING BAD
POWER TRACE,) SOLDER JP3, AND LEAVE JP1/JP2 OPEN.

MCAD/Structure

TBD

Resolves #1114

Motivation and Context

Intent is to test power regulation/protection on ALE then trickle down to all other pro-micro based PCBs. This should bypass pro-micro's with faulty regulators or the trace that creates a short to ground and protect the ABSIS Bus from USB power from the pro-micro.

Type of change

Please delete options that are not relevant.

• MCAD - Revision (Revision of an MCAD model)
• ECAD - Revision (Revision of a PCB or the interconnect)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration:

ECAD changes are untested but built on success of previous iterations.

Screenshots:

Added this circuit:

Checklist: (Delete non-relevant sections)

MCAD:

• Design intent and requirements have been met?
• Design has been fit checked to ensure no interference exists with any other components?
• Design has been integrated into Next Higher Assembly (NHA)?
• Drawing has been revised, (i.e. Rev - to Rev A) with all changes described in Revision Description Block?
• Did the parts list change?
  • If yes:
  • Master Parts List (OH-MPL) update required due to change? (PR will not be accepted without MPL changes integrated.)
• Drawing Tree (OH-DWG-TREE) update required due to change? (Mostly just new MCAD parts will require this. PR will not be accepted until Drawing Tree updates are completed, or an issue is generated detailing what changes need to be made.)
• Interconnect (OH-Interconnect) update required due to change? (Does this need to plug into another part or assembly electrically? PR will not be accepted until interconnect updates and interconnect BOM is updated.)
• Has the PDF of the drawing been named as the next version and placed in the release folder with the correct filename?
• Have all required manufacturing files been generated, named correctly, and placed in the correct location in the release folder?

PCB/ECAD:

• Requirements definition completed as a note on the schematic?
• Schematic completed?
• PCB laid out?
• PCB routed?
• PCB constrained by physical footprint limitations?
• PCB critical component location requirements met?
• Version number updated on PCB silkscreen, and the PCB and schematic docs?
• Schematic/PCB reviewed?
• BOM generated?
• Gerbers generated?
• MCAD generated?
• Has the fabrication files and a PDF of the schematic been copied to the ECAD folder of the release folder?

[amanuense]

The MIC5219 will most likely burn. I estimate that if we need continuous 500mA the max Vin is 5.81v

logic behind it:

lets start with power disipation

if we assume SOT23 at a 20c ambient (being optimistic)
that gives us a Pd(max) of 477mW. 30c = 431mW and so on.

we calculate vin from using this formula

and assuming 12mA Ignd we get vin = 5.81v

then we realize there is a literal example on the next page which estimates Ignd as 20mA and Vin = 5.6v

so I have a question. what is the realistic expected continuous current load?

[amanuense]

IF 12v->5v is a must. I recommend a switching power regulator. a cheap buck regulator will do the trick. something like https://www.mouser.com/ProductDetail/Texas-Instruments/TPS560200DBVR?qs=igp4D3uu33JvyBesN3zBxg%3D%3D will do the trick just fine.

the datasheet already precalculates the values you need for 5v

the most complicated part about switched power supplies is that

• they add noise. this one expects 10mv ripple
• PCB layout can be a little annoying if you care about electromagnetic emmisions. I can provide some documentation on how to place stuff. however the datasheet provides a good reference. a little large but good enough for ABSIS.
  

[amanuense]

good news! TPS560200DBVR is a jlcpcb jellybean C83671

[amanuense]

Updated power stage for ABSIS ALE to use a SMPS

this new configuration will have a 80% efficiency with 5V output at 100mA. I'm unsure if we need to add an RC snubber

notes for PCB layout, the layout defined on the datasheet
https://www.lcsc.com/datasheet/lcsc_datasheet_1811151523_Texas-Instruments-TPS560200DBVR_C83671.pdf
is good enough but can be improved. specially it can be made smaller by using both sides of the board or by using clever part placement.

if for some reason I can't do the routing. please take a look to this guide.
https://www.ti.com/lit/an/slyt614/slyt614.pdf

[amanuense]

note there are other buck converters that might do the job for cheaper or with smaller foot print but the one I selected is readily available on JLCPCB.

TI has a nice tool to get designs for power supplies
https://webench.ti.com/power-designer/switching-regulator/select

I'll see if I can find another jellybean I can use.