In Shenzhen, China, recently I met with a designer for an infotainment systems manufacturer. “Do you happen to use any 60V load switches in your design?” I asked. He affirmed, telling me he incorporated about 10 30V-60V small-outline transistor (SOT)-23s on his board, generally around 100mΩ RDS(ON). “And on these boards, are you space-constrained?,” I asked. Turns out that he was, so I showed him information on TI’s new CSD18541F5 60V FemtoFET MOSFET, coming in at just under 60mΩ with a 1.5mm-by-0.8mm (1.2mm2) footprint (see Figure 1), that was designed specifically for space-constrained applications such as infotainment systems.
Figure 1: CSD18541F5 land grid array (LGA) package
That’s roughly one-sixth the size of an SOT-23 (6.75mm2) package for those of you keeping track at home (see Figure 2). It also represents an RDS(ON) multiplied by footprint size figure of merit that is 75% smaller than traditional MOSFETs.
Figure 2: Traditional SOT-23 package next to the CSD18541F5 LGA package
Doing some quick math with this engineer, we determined that with 10 devices per board, he’d be saving roughly 55mm2 – not an insignificant amount for a device generally considered an afterthought by most engineers. And what about pad pitch? Fortunately, the tiny LGA package was designed to accommodate industrial customers as well, for whom the consensus seems to be that a 0.5mm pitch is the preferred minimum distance between pads.
Today, almost everyone I visit in the industrial market, whether they’re manufacturing power supplies, battery protection or power tools, has had some interest in either a smaller- or higher-performing load switch (or both).
So if your industrial design features more than a few SOT-23s or larger load switches, consider switching to our new CSD18541F5 MOSFETs. Trust me, your PCB footprint will thank you later.
The story continues...
Then the customer from Shenzhen designed the CSD18541F5 into his product, only to later realise that there is no distributor stock available anywhere on the planet. He had been sold a vapour-ware concept. Having spent all his development budget, and with no product to deliver, he went bust.
The moral of the story is: Don't believe the adverts until the product is available from a local distributor. With TI, there's several years lag between them, and no guarantee the product will ever exist.
I apologize if you have ever had this problem with TI in the past. As a policy, we always notify the distributors when a product is released but we do not and can not force them to purchase stock.
For the record, this part was released to market 5/17/2016 and samples were immediately available for purchase on the TI store at ti.com. By the way, this is the case with any active part TI has.
If you ever have trouble obtaining samples of a TI part from a disti in the future, please reach out to your local sales support or try posting on our E2E forum for assistance.
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