Identify Components by SMD code

[Wilksey]

Hi,
Can anybody help identify the 2 components in the picture?

One has what looks to be 731 B34 and looks like the On Semi logo, the other looks like is has 73 4A, I am presuming these are diodes as they go across the VCC + GND points.

I think the large one is a zener of some kind and the smaller one is a TVS perhaps, the power comes in (3V3 or 5V) goes to a fuse, then passes by these and then connects to a E2PROM chip, standard 8KByte Microchip 25LC641.

Cheers

[fzabkar]

"B34" could be a Schottky rectifier:
https://www.onsemi.com/pdf/datasheet/mbrs340t3-d.pdf
http://www.smdmark.com/en-US/search/code?id=B34

I expect that "4A" would be a 5V TVS diode.

The former would provide reverse polarity protection while the latter would handle overvoltages.

[gamalot]

The one in the SMA package should be a 5.6V Zener diode 1SMA4734A.

https://html.alldatasheet.net/html-marking/1296757/LEIDITECH/1SMA4734A/1143/2/1SMA4734A.html

[fzabkar]

The one in the SMA package should be a 5.6V Zener diode 1SMA4734A.

https://html.alldatasheet.net/html-marking/1296757/LEIDITECH/1SMA4734A/1143/2/1SMA4734A.html

I think that "73" may be a date code.

This is what a 1SMA4738A looks like:
https://www.taobao.com/list/item/599114971429.htm?spm=a21wu.10013406.taglist-content.4.673b990byuSgrY

[whatboy]

https://www.s-manuals.com/smd

[Wilksey]

Thanks for all of your replies,
I looked at a SMD code table but it didn't make sense for "4A" to be a 2V zener, but I did find another reference to a TVS with 4A markings.
The larger one could well be a schottky diode, I don't get continuity through either of the diodes in either direction, which made the think it is not a simple diode.

I have since discovered that VCC also goes into a TVS diode as part of a chip like this: https://www.diodes.com/assets/Datasheets/ds31271.pdf

Would there be 2 TVS diodes on the VCC line?

I have seen a picture of another similar circuit which has a large black diode and that part number actually shows it as a 5.6V 3W zener, but I can't see one with B34 markings.

[fzabkar]

There are plenty of "B34" images here:

https://www.google.com/search?q=mbrs340t3&tbm=isch&tbs=itp:photo

[Wilksey]

Yes, the more I look at it the more I am convinced you are right with the Schottky barrier diode,

So do you think the smaller one "4A" is more likely to be a TVS or a zener?

[gamalot]

The one in the SMA package should be a 5.6V Zener diode 1SMA4734A.

https://html.alldatasheet.net/html-marking/1296757/LEIDITECH/1SMA4734A/1143/2/1SMA4734A.html

I think that "73" may be a date code.

This is what a 1SMA4738A looks like:
https://www.taobao.com/list/item/599114971429.htm?spm=a21wu.10013406.taglist-content.4.673b990byuSgrY

Zener diodes with this part number can come from many different manufacturers, and they don't necessarily have the same marking layout.