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Obsoleted BZX55C12 - partnumber changed?

beta22

Obsoleted BZX55C12 - partnumber changed?

Postby Kernle 32DLL » October 13th, 2018, 9:46 am

On first glance, it seems that the BZX55C12 (and variants), as used for many AMB projects, seem to have been discontinued (I post this in the β22 board, as BZX55C12 and variants can be substituted in σ22/11).

Moreover, entering e.g. the 512-BZX55C9V1 part number on mouser (9.1v variant of BZX55C12, as mentioned in the σ22/11 documentation) leads to a discontinued ON Semiconductor / Fairchild diode, which does not align with the linked Vishay datasheet and the important low noise characteristics mentioned in the β22 documentation (some specs are way off, too - although I cannot tell if this is of importance).

However, if I don't get this totally wrong it seems that just the naming scheme has changed. Manually searching for a Vishay 12v diode, I turned up BZX55C12-TR (78-BZX55C12). This seems to be the original BZX55C12 diode, and the datasheet (same as on the AMB page) confirms that the TR suffix should be correct order number in the first place.

Digikey also reflects this, by listing the original BZX55C12 (BZX55C12-ND) as an obsoleted ON Semiconductor one, while offering BZX55C12-TR (BZX55C12CT-ND)

So - has the naming scheme changed, or am I overlooking something? The only difference I see is packaging (Cut Tape, etc.), which I don't care for.
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Obsoleted BZX55C12 - partnumber changed?

Postby amb » October 13th, 2018, 11:39 am

The part is not obsolete. The base part number is BZX55C12, but it refers to parts packaged in bulk (i.e., loose parts). That style of packinging is being phased out (just like the straight-pin TO-92 devices mentioned before). The -TR suffix reflects the same device packed in tape reel (for ease of use in automated PCB assembly). You can cut the devices off the tape to use for manual soldering.

In mouser’s stock number, 512- refers to Fairchild Semiconductor which has recently been acquired by On Semi. They no longer manufacture the BZX55C12, bu Vishay still does, and is equivalent.

You could have avoided all these confusion by ordering these parts from AMB audio shop along with the PCBs. There would have been no question that they are the correct parts,
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Obsoleted BZX55C12 - partnumber changed?

Postby Kernle 32DLL » October 13th, 2018, 3:03 pm

amb wrote:The part is not obsolete. The base part number is BZX55C12, but it refers to parts packaged in bulk (i.e., loose parts). That style of packinging is being phased out (just like the straight-pin TO-92 devices mentioned before)


Duh... I really don't get why manufacturers do this. Also, it does not help that Mouser suggest the BZX79C12 as a replacement, when there are other manufacturers still making the same part

amb wrote:In mouser’s stock number, 512- refers to Fairchild Semiconductor which has recently been acquired by On Semi. They no longer manufacture the BZX55C12, bu Vishay still does, and is equivalent.


Well, the datasheet for the Fairchild / On Semiconductor variant nowhere mentions it being low noise, whereas the Vishay one does. However, I have no idea how to tell how equivalent they are (same part, different manufacturers), so thanks for the clarification!

amb wrote:You could have avoided all these confusion by ordering these parts from AMB audio shop along with the PCBs. There would have been no question that they are the correct parts,


Thats true, but wheres the fun in that?
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