What do you do when the datasheet is wrong? - Page 1
Forum section: electronics / general

author: sarfata
author_rank: Contributor
timestamp: November 09, 2012, 12:14:23 am
content: I used a FDC654P PNP Mosfet in one of my recent project as a reverse-polarity protection diode.Ordered the boards, built it and I had an obvious short-circuit. I quickly identified that this mosfet was responsible and replaced it by a solder bridge.Taking a closer look at this problem today. The board was ok, the datasheet is wrong:http://www.mouser.com/ds/1/149/FDC654P-48962.pdfIf I test pins 1 and 6 for continuity, I get a negative result but 3 and 4 are shorted. Basically it's backwards.Would you assume that the datasheet is wrong? Or that the markings are faulty in this batch of components?thomas

author: tom66
author_rank: Super Contributor
timestamp: November 09, 2012, 12:18:27 am
content: I would assume that the pin out would be the -last- thing they would get wrong. Maybe some odd specification like on-resistance, gate charge etc. I would suspect the marking isn't what you think it is. I have seen SOT-26 with what looks to be two markings but only one is the actual dot.

author: sarfata
author_rank: Contributor
timestamp: November 09, 2012, 12:27:01 am
content: You are probably right. I can see another dot on the other side but it is part of the marking ".654" (the datasheet mentions that first . as part of the marking). This dot actually seems to be the one to consider so I am not sure what the other one, alone on the other side is ...Wish I had Dave's microscope!

author: nitro2k01
author_rank: Frequent Contributor
timestamp: November 09, 2012, 02:01:58 am
content: A "PNP Mosfet" eh? Why use a MOSFET as a diode? Are you using it as a switch as well. (If you're using it for reverse protection I don't see how you could use it as a switch, but...) If you're not using it as a switch, let me ask you, where do you connect the gate?

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: November 09, 2012, 03:11:55 am
content: I have encountered counterfeit parts before. Since you quote mouser I think you may be safe if thats where you obtained them from. Ebay or alibaba-bah are a shitfest of chinese fakes. The power nfets I bought were not true IRF but at least the pin outs matched.

author: sarfata
author_rank: Contributor
timestamp: November 09, 2012, 03:26:43 am
content: nitro: This was suggested to me here on this forum by Pak_engineer.This technique is very well explained here:The main advantage is to reduce power loss. Even a schottky diode has a forward voltage of 0.3/0.4V but this PNP mosfet has a Rds of only 75mOhm when turned on. That's 0.225V at 3 amps which is a significant (/2) difference!The gate is simply connected to ground. The video explains that very well.chickenHeadKnob: Yeah, bought from Mouser so they are probably not counterfeit.

author: JuKu
author_rank: Frequent Contributor
timestamp: November 09, 2012, 06:33:16 am
content: Quote from: sarfata on November 09, 2012, 03:26:43 am...so if they are counterfeit or wrong parts, I probably get my money back. <= correctedI've received parts with wrong markings directly from manufacturer; i.e. I ordered part x and received parts that were marked as x, but were something else; a genuine error from their part. Well, those boards were easily sold:-). My company has also received counterfeit op-amps from manufacturer's distributor. That one was never fully find out; a warehouse worker side business remained the most likely explanation.Nowadays I would suspect, in order:1: Myself or my interpretation of the datasheet.2-7: Ditto.8: Wrong part, especially on components that don't come in full reels.9: Counterfeit part, if they came from anywhere else but factory rep. As noted, distributors can be tricked, factory rep maybe not so easily.10: Datasheet error. Not in pinout, though. But the more complex the part is and less used, the more likely you hit on something that no one else has so far. I can tell 5 or 7 issues on the DSP I'm currently working with where it does not behave like the datasheet says. (Most of the nature of: datasheet says A. Normally so, but if condition B or you manage to do X in certain timeframe, then A becomes something else.)11: With programmable parts, after making sure my code is correct (and re-checking one to ten thousand times or thereabouts): The compiler. I once spent a month first finding out and then proving, that the compiler produced working code but with different logic than the source.12: Error in marking of the part. Usually the factory knows what they are making at a given moment, but not always, see above. Humans run the factories, too.13. Something I've not seen before. And as you can see from the list, I've seen a lot.

author: Gall
author_rank: Frequent Contributor
timestamp: November 11, 2012, 05:18:21 pm
content: I found an error in OPT101P datasheet some time ago. It was in math formulas (multiplication instead of division) and resulted in the wrong number (sensitivity value) printed in datasheet. Fortunately the correct value can easily be calculated from basic physics, as I did.

author: free_electron
author_rank: Super Contributor
timestamp: November 11, 2012, 07:08:25 pm
content: i dont think the datasheet is wrong ... basically all the powermosfets in sot23-6 package have gate on pin 3 .. 1,2,5 and 6 are shorted