<whitequark>
this came up before; the foldback current limit behavior of it is pretty unique
<d1b2>
<esden> @whitequark That is why I am asking. Because this is the last showstopper part missing before we can build the Glasgows. The current delivery estimate for at least some of them (I still have 0 of them) is January 2022. The full qty is estimated for December 2022. There are some from an obsolete part supplier for 10x price. Which I am considering to pay but only for the early birds. It is not an option for the full production batch. This means we
<d1b2>
either have to find the parts somewhere else or find a replacement.
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<d1b2>
<esden> So it would be very good to find a compromise here and replace it with some other part. If we want to deliver Glasgows in any reasonable timeframe...
<whitequark>
then we'd have to re-qualify the overcurrent shutdown behavior
<whitequark>
possible, but comes with its own issues and delays
<d1b2>
<esden> then let's get on it 😉
<d1b2>
<esden> current delay is December 2022 ... that is next year...
<d1b2>
<esden> if we don't do anything
<d1b2>
<esden> again, unless we can find a source that has 8k of the part, that will not cost arm and a leg.
<whitequark>
there's some suppliers locally that list some in stock
<whitequark>
I'll call them tomorrow
<d1b2>
<esden> Sounds good! 🙂
<d1b2>
<esden> Thank you! 🙂
<whitequark>
what is the best price you currently have?
<d1b2>
<esden> just a sec
<d1b2>
<esden> When I was calculating the BOM cost the price was $0.41/pc the price I finally got them for with the aforementioned leadtimes is $0.49/pc
<whitequark>
do you need 8k or 12k?
<d1b2>
<esden> yeah checking the bom... I think we just need 8k as there are 2 per board... for a 4k build...
<d1b2>
<esden> "just" 😉
<whitequark>
so, just to be clear
<whitequark>
the two options are "we find 8k of the part" and "we redesign it"; nothing in between you'd suggest?
<d1b2>
<esden> The option "in between" is we get less than the 8k to build the early bird or a bit more than that. And then redesign for the remainder... not sure what else we can do.
<d1b2>
<davoid> what are the key features that you need that makes TPS731xx "the one"?
<d1b2>
<esden> I think the main concern with replacement parts is the overvoltage protection specs on the part.
<whitequark>
hold on, let me ask the person who looked into replacing it
<d1b2>
<esden> As it is the part driving the supply to the banks. This is an important parameter.
<davidc___>
ricoh claims their LDOs have foldback current limiting. I can't say I claim to understand exactly how we rely on TI part's protection, so I can't say if they fit well or not
<davidc___>
(also, I didn't see stock available; but distributors claim 9 weeks leadtime, so there's a good chance they aren't available either)
<whitequark>
esden: how many do we need for early birds? 800?
<whitequark>
also, it's possible that the DBVR suffix will be easier to source. do you think it's worth considering redesigning for that?
<whitequark>
or can we not fit that on the board?
<d1b2>
<davoid> i had a look at the datasheet. indeed nice with rcp and current limit built in. quite unique for this type of ldo. but.. was ever a standard LDO considered + adding a current clamp or current limit in series on its output? most lf those would give both rcp and flexible current limiting/ short protection. price might be 0.2-0.3USD + thr ldo of course
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<d1b2>
<esden> @whitequark For the early birds we need at least 400 of the chip. As there are 200 Glasgows in the early bird batch. Redisigning for a different footprint is definitely "easier" than having to reevaluate for a completely different part.
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<whitequark>
esden: thank you. looking into it
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