Author Topic: Any ideas what this IC does?  (Read 920 times)

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Offline Mario87Topic starter

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Any ideas what this IC does?
« on: August 03, 2019, 04:06:29 pm »
Hey all, as per the title really, I have an IC on a board and no idea what it does. The only marking on the top is "5C". I've uploaded a couple of pics below. On the first image the IC is circled in red with pin 1 marked by the red dot next to it. The 2nd image shows the IC removed.

The IC interfaces with the sim card slot that would normally be below it, on the left of the board.

Pinouts appear to be as follows....

Pin 1 - CLK pin on Sim Card Slot
Pin 2 - GND
Pin 3 - Not Connected
Pin 4 - VCC pin on the Sim Card Slot and the decoupling capacitor located to the right of the IC
Pin 5 - RST pin on the Sim Card Slot
Pin 6 - I/O pin on the Sim Card Slot

So it clearly interfaces with the sim card and does something, the question is what?!

Anyone got any ideas?

Thanks



 

Offline james_s

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Re: Any ideas what this IC does?
« Reply #1 on: August 03, 2019, 04:17:16 pm »
Is it a supervisor IC? The fact that it interfaces with reset suggests it might be.
 

Online SiliconWizard

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Re: Any ideas what this IC does?
« Reply #2 on: August 03, 2019, 04:30:11 pm »
Given it connects to PS and IO pins of the SIM card, I'd suspect it could be some kind of transient voltage suppressor.

The following gives you a few references to look at:
https://smd.yooneed.one/code3543.html
 

Offline DaJMasta

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Re: Any ideas what this IC does?
« Reply #3 on: August 03, 2019, 04:34:15 pm »
Yeah my guess would be TVS as well, I know of a few for use on USB data lines in that form factor... that said, the pin connections would make more sense as some sort of supervisor, but I don't know of this being required in other sim card designs.

Does it operate?  Could you scope the pins and see if it's doing something active?  Maybe diode check out of circuit to see if you can buzz out some TVS diodes instead?
 

Offline IDEngineer

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Re: Any ideas what this IC does?
« Reply #4 on: August 03, 2019, 04:45:55 pm »
Another vote for a TVS, a multichannel one since you traced three signals to it and it has connections to both supply rails. Any markings on the bottom of the package?
 

Offline Benta

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Re: Any ideas what this IC does?
« Reply #5 on: August 03, 2019, 04:50:07 pm »
Yep, ESD protection array.
 

Offline Mario87Topic starter

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Re: Any ideas what this IC does?
« Reply #6 on: August 03, 2019, 04:58:12 pm »
Thanks all! After seeing the posts above I did a bit more digging and found schematics of another circuit, very similar to the one I am working with. Funnily enough, there is a 6-pin IC connected to the Sim Tray Slot in a very similar fashion and it's called out as "SMF 05C".

After a quick google, this is indeed a TVS Diode Array for ESD protection.

Even found the datasheet.... https://www.semtech.com/uploads/documents/smf05c.pdf

Many thanks all!
 


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