Digikey non stocked items - Page 1
Forum section: electronics / projects

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 05, 2012, 09:24:14 am
content: After jumping on the design merry go round (I think Dave had an episode about it) I finally found my part and decided to get off.I looked up Digikey and found my part was in fairly limited supply. Mostly non stocked but one foot print had some stock. But not in the quantity to give me confidence.The part is LTC4442http://www.digikey.com.au/product-search/en?x=0&y=0&lang=en&site=au&KeyWords=ltc4442My question to anybody with any experience on this is, am I safe to incorporate this chip into a design and expect to be able to buy it in quantities of say 50 every 6 months for 5 years to come?Or should I look at other chips:I am after a basically a 2 output synchronous gate driver with a charge pump for the high side and a max input supply voltage to suit a 20v open circuit solar panel.the LT1158 seemed suitable but the drive current was a bit low.Any chip suggestions would be welcome but the ltc4442 is actually exactly what I want.

author: digsys
author_rank: Unknown
timestamp: November 05, 2012, 09:50:19 am
content: I've designed in many parts from LT, many are totally unique to them. You just have to trust they'll be around for a long time,and based on their past, it's a pretty good assumption. Not to say there won't be shortages, for any number of reasons.If a part is important to me, and I have MANY, I make sure I order at least 6 months worth. Worst case, I pay a little extra tobuy it (them) from 2nd source warehouses, part miners etc. If you feel you have the perfect part, go with it. LT are OK.Edit: There are other distributors besides DigiKey. Always check the manufacturers site for "lifetime / status" of any part.

author: jeroen74
author_rank: Frequent Contributor
timestamp: November 05, 2012, 10:55:38 am
content: And LT has their own store as well from which can do credit card purchases.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: November 05, 2012, 11:35:15 am
content: Have you looked at Microchip's range of gate drivers? Microchip typically have better availability and pricing than any other manufacturers.Microchip are one of the few suppliers I'd never have any doubts about designing into anything.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 05, 2012, 12:25:38 pm
content: Thanks digisys, jeroen and Mike,I was hoping somebody else had run into a similar situation and I can see it may be quite common with LT as they have such a range of weird power chips.Our company tends to buy boards fully loaded, so I can't really stock up. They just want to send the design files and get another batch.Incidentally I just noticed an old pick and place machine and an infra red solderer just landed downstairs in the factory. But unfortunately I wont get a chance to play for the foreseeable future.I did check the other suppliers via findchips to give me a rough idea of quantities, but that is what scared me, not many people seemed to be using it and it think it is relatively recent circa 2007.I didnt know you could by direct for LT but often if you're from Aus the buy now link just redirects to a distributor. I sometimes buy direct from Microchip though, they only charge $15 postage.I saw one datasheet from Microchip, but from memory it looked to old. Maybe I should look direct at the site, but I've seen enough datasheets to last me for the rest of the week at least.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 05, 2012, 11:11:43 pm
content: I have recieved info back from Linear Technology.QuoteBut in the interim I have changed to the LTC4449 which seems to be newer has more available and the only difference is that its boost circuit produces a lower voltage for the fet gates. But seeing that you can get amazing fets these days with a 2-2.5v threshold, sub 10mOhm, then you probably save power by not driving the gate so hard.So LTC4449 it is.I might use the PSMN9R0-30YL fet with it.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 06, 2012, 03:25:23 am
content: I just got a second email from them. with a link to their policy on this.www.linear.com/docs/40741Here is an excerpt which seems reasonable enough.It is LTC’s general policy that when a product is discontinued we notify our sales force and ourdistributors and customers who have purchased the product that the item is being discontinued.At the time of notification, customers have 6 months to place orders for the item and they mayschedule deliveries for up to 6 additional months beyond the final order date. In some instances,LTC will entertain requests and proposals by interested customers to continue to manufacture thedevice via a special agreement, providing LTC has viable commercial and technical ability tomanufacture it.

author: jeroen74
author_rank: Frequent Contributor
timestamp: November 06, 2012, 07:42:23 am
content: The chances of an LT chip becoming unobtainium is far less then, say, ICs that are typically used in the PC world, made by obscure far-east brands.I once used a PCI UART chip and it became unobtainium within two years or so. Luckily this was a very low volume product (just tens in total) so we did a lifetime buy just to be sure, and guess what, we still have a small tray full of them that's been collecting dust for 8 years now. Later on the customer wanted the product to use USB instead of PCI, so I guess the tray is going to collect some more dust

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: November 06, 2012, 10:13:57 am
content: Yes PCI to serial, the more dust the better.I do like it when clients want to upgrade and redesign, makes support so much easier.

author: nrclark
author_rank: Newbie
timestamp: November 07, 2012, 05:15:23 pm
content: Linear is great about their old chips. They will directly sell you tons of chips that distributors have stopped carrying. If I was forced to design in an almost-out-of-production chip, it would definitely be one made by Linear.