component hunt: some results

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component hunt: some results

Werner Almesberger
I've written an ECN discussing the situation of components that are in
our design but no longer in FIC's inventory, i.e., the ones we'll
certainly have to source ourselves:

http://svn.openmoko.org/trunk/gta02-core/docs/ecn/ecn0045.txt

I'd be particularly interested in feedback on the possible replacements
for USB boost converter (U4904), and in help with the search for better
substitutes for the battery connector (CON1701) and the audio jack
(JK4401).

Also, if someone can find a distributor who has the PMU (U1701) and the
GPS receiver (U7601) in small quantities, that would be great.

Regarding the other hot topic we have at the moment: the search for a
"cashier" - or, better, treasurer - and perhaps an organization to give
all this the proper structure is still in progress. It seems that the
best approach is indeed to set up some form of organization, but what
will work best and where still needs a bit of investigation. I hope
we'll have more news early next week.

- Werner

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Re: component hunt: some results

AlvieBoy
Werner Almesberger wrote:
> I'd be particularly interested in feedback on the possible replacements
> for USB boost converter (U4904), and in help with the search for better
> substitutes for the battery connector (CON1701) and the audio jack
> (JK4401).

I've tried searching for AAT1275 replacement, and no luck so far. However, at least TI has some power controllers able to provide at least 400mA. Others can go
up to 1-2A, like USB hub power supplies.

I wonder if this is a good idea to use a USB integrated HUB and perhaps leave some pcb traces so one can connect more devices to it.

Depends a bit on what we do want - just a 5V, 500mA-limited power supply ?

> Also, if someone can find a distributor who has the PMU (U1701) and the
> GPS receiver (U7601) in small quantities, that would be great.

Hard. Those are typically short life components, maybe we should just replace them with similar (on purpose) parts. PMU should be fairly easy, GPS perhaps not.

> Regarding the other hot topic we have at the moment: the search for a
> "cashier" - or, better, treasurer - and perhaps an organization to give
> all this the proper structure is still in progress. It seems that the
> best approach is indeed to set up some form of organization, but what
> will work best and where still needs a bit of investigation. I hope
> we'll have more news early next week.

I hope so too. And time to revive gta02-core blog. I believe we do have again enough stuff to put there.

Álvaro

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Re: component hunt: some results

Werner Almesberger
?lvaro Lopes wrote:
> Depends a bit on what we do want - just a 5V, 500mA-limited power supply ?

Yes, 5 V, limited to something close to 500 mA, with an active-high
enable input, and shouldn't act up if disabled and there's a voltage
on the output.

I've listed a few candidates in bom/research/u4904. Perhaps the
ADP2503ACPZ-5.0-R7 wouldn't be all bad. Would be good if someone
could check that I haven't overlooked anything that could cause
trouble.

> Hard. Those are typically short life components, maybe we should just
> replace them with similar (on purpose) parts. PMU should be fairly easy,

Whoa ! I should frame this, nail it to the wall, and show it to any
Openmoko veteran who comes visiting ;-)

You have no idea of the amount of suffering that went into finding a
suitable PMU and getting it to do what we want. In part it's due to
the somewhat quirky structure of this PMU, with mask-programmed reset
behaviour, but a lot is also just discovering all the corner cases.

It's already quite a ride to make sure the right rails come up with
the right voltage at the right time to get the CPU out of reset,
while making sure that each of these rails has a suitable current
rating, and no other rails are doing anything evil (such as feeding
too high a voltage into some component or subsystem) while the CPU
is still rubbing its eyes.

Naw, I'd be very afraid of changing the PMU.

Changing GPS is also tricky. It may be an option, but any new design
is likely to come with a lot of changes, so I'd rather avoid this,
too.

Of course, if you have some specific components in mind with
sufficiently open documentation, good availability, no need of new
drivers, etc., then it can't hurt to have a look at them. I would
still be very reluctant to change the PMU, even to a different
variant of the PCF50633, because one small slip may mean that the
board never even starts to run, but we can take larger risks with
less critical subsystems.

> I hope so too. And time to revive gta02-core blog. I believe we do
> have again enough stuff to put there.

Whee ! We have press coverage again ! :-)

- Werner

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Re: component hunt: some results

Werner Almesberger
In reply to this post by Werner Almesberger
I wrote:
> I'd be particularly interested in feedback on the possible replacements
> for USB boost converter (U4904), and in help with the search for better
> substitutes for the battery connector (CON1701) and the audio jack
> (JK4401).

Did anyone find something ?

Meanwhile, the SN74AUP1G00DCKR (U4902) on the way to Digi-Key have
arrived and they have plenty of stock of this non-stock item now.
I've thus lowered its priority in bom/research/STATUS. Good things
come to those who wait :-)

Alas, the nice Murata 10 uF 10 V X5R 0805 capacitor is no longer
available. I've added an equivalent part from Kemet. Our score is
now:

SVN Rev -- No source -- -- Digi-Key --  -- Farnell ---  --- Mouser ---
        Short   Missing Parts   Price   Parts   Price   Parts   Price
r5913    8      11      85      1436 2      UKP 52   1       134

Now, let's move forward with the replacements. Is everybody fine
with the following two substitutions ?

Samsung K4M51323PC-DG75 -> Micron MT48H16M32LFCM-75:B
Proconn SMSN16-J0-2214 -> Amphenol 101-00492-20

The former needs a slightly different footprint (the package outline
changes, the balls don't), while the latter needs an update of the
schematics, the footprint, and probably also the circuit symbol.

- Werner

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