BSP297 backorder

Hello Folks,

Just saw that the BSP297 (200V n-channel, 4.5V Vgs rated, 2-3 Ohms Rdson) is on backorder at some places. Any hunch whether that could persist? Alternatives in SOT223?

Regards, Joerg

Hello Winfield,

Thanks, Win. I had scoped out all the domestic sources including IRF. Thing is, they might advertise them as logic-drive but when the data sheet only specs 10V Vgs I can't design them in. In med electronics stuff needs to be in writing and it can't be just "typical". There must be a min and max like on the BSP297 data sheet.

When you look at the typical values like figures 1 and 3 on the IRFL214 data sheet it seems that it can't even hold its water at 100mA when driven 4.5V. In my case it would deliver quite a pyrotechnic show.

There is the Vishay Siliconix TN2404KL. It's SOT23 so I'd have to parallel some more. Unfortunately that one doesn't seem to be too common in the US either.

Regards, Joerg

ZVN 4424G Zetex works specified on 2.5V, but has 6R on resistance

--
ciao Ban
Bordighera, Italy

Would availabilty perhaps be related to it being an 'oddball' pro-electron designated part ?

Graham

That looks like a nice part. Rdson seems a bit high for SOT223 but other than that it is great.

Regards, Joerg

Hello Graham,

IIRC it is easily available in Europe, just not so much in the US. So far I haven't found anything comparable here. Can't be a boutique part because it is cheap. Also, there is a huge market for HV FETs that are truly logic level and not just hyped up as such by Marketing.

Regards, Joerg

I'm sorry, I would have sworn the part I was suggesting had a 4.5V logic rating, perhaps it was a different part.... Weird.

--
 Thanks,
    - Win

Ouch, I'm afraid I know how they think you're supposed to use that package! 52 watts with Tc = 25C, hah!! It's tough to keep a FET "case" cool by conducting to some PCB copper. I'll bet 5W will be the most you can dissipate, which reduces the Id-max spec down to sqrt [5/(0.115*2.2)] = 4.5 amps for Tj = 150C. That's much more realistic than the 14.5A datasheet number you were impressed with. But, OK, compared to some of the wimps out there, it's impressive.

--
 Thanks,
    - Win

Who is the everybody you're talking about? What market?

--
 Thanks,
    - Win

Nah. Not weird. Just a contact high. %-}

Cheers! Rich

Hello Winfield,

Now this is a really hot one, the Si7606DN:

It says works in progress so I guess we have to be patient. They'll enjoy a cash cow when it comes out. If the pricing is set right, that is.

I wonder how they achieve such good low Vgs performance with these high voltage devices. Do they have the superior process? Maybe Jim could shed some light here.

Anyway, the "real" logic level devices would probably warrant an entry in one of those parts tables in the new edition of AoE. No, I am not going to ask when .... just bit my tongue.

Regards, Joerg

Hello Winfield,

Most parts with a true logic rating are low voltage FETs. When you need

100V or more in a small SMT package it quickly whittles down to less than a dozen. What really surprised me was that the domestic manufacturers don't seem to have any.

Anyway, a short list in the new AoE edition would save lots of engineers what I just had to go through (again). It was especially tedious because many European mfgs don't seem to have a clue how to design an efficient web site.

Can't wait until that Si7606DN comes out.

Regards, Joerg

Hello Winfield,

Yes, that looks like the usual marketing fluff. Only in outer space or something like that. I would never exceed a watt with that tiny package.

Thing is, you don't have to. Pulse current capability is all that counts in most switcher applications. The device has to hold it down at several amps because if it gives and Vds rises an impressive disintegration will happen in milliseconds.

If you look at the first figure (why didn't they number them?) it holds Vds down to about 300mV at 4 amps while driven at 4V. Somehow they must have found that magic sweet spot in the TrenchFET process or at least they think they are close enough to release preliminary data. Now they have to price it right or everybody will stay with their bipolar solutions.

Regards, Joerg

Hello Winfield,

Mostly smaller switch mode applications where you have to generate a few watts. Voltages range widely, mostly buck conversion. In my current case it's a variable output that needs to go from 0V to 100V (SEPIC) but there is only a logic level supply.

You could use a tiny xfmr to step up the drive but that often isn't in the cards for cost reasons.

Other markets are relay and solenoid drivers, valve drivers and the whole telephone (POTS) range. All very cost sensitive. A few times I even shunned my old favorite BSS123 because it was 5c versus 2c for a BJT with a resistor. For fast apps the BJT also needs a cap to clear the charges faster but then it's still less than 5c total. BJTs do become more expensive when you need more than 80-100V so the FET mfgs have some wiggle room. But not a whole lot.

Regards, Joerg