SICSTOCK chinese semi franchise - opinions?

[redwire]

I'd ordered from eBay store SICSTOCK, I installed the TC835 DVM IC and it ran for 5 minutes and then strangely failed dead short from +5V to -5V. Sigh.

Anyone else deal with these SICSTOCK guys, they seem like a large chinese franchise.

The Microchip PDIP-28 looked legit but had a small chip on one end.

Just weird to see a part work for a few minutes then die. The circuit and old ICL7135 work fine, so I think bad silicon.

[eccerr0r]

Re: SICSTOCK chinese semi franchise - opinions?

Were you trying to turbocharge a DMM? (I'm tempted to upgrade my B&K 2833...)

That is indeed weird that it failed shorting out, usually bad dies don't get packaged. I wonder if it was mishandled and finally let out the magic smoke...

[stj]

Re: SICSTOCK chinese semi franchise - opinions?

was it wanting 3.3v and got 5v?
or maybe some other pinchange you didnt notice?

[eccerr0r]

Re: SICSTOCK chinese semi franchise - opinions?

According to the datasheet, they should be mostly compatible with each other, certainly not enough to damage it. But I was wondering if it was just ESD mishandling perhaps.

[redwire]

Re: SICSTOCK chinese semi franchise - opinions?

UPDATE: bench ESD mat was not grounded, so the vendor may not be to blame.

The chip was running OK for a couple minutes and I pressed a V/A/ohms button a few times and poof the display went out.
Found the PSU overloaded and pulling the IC out, 3ohms between -5V and +5V pins. Didn't short to GND or anything else. Put in the old IC and it works fine.

OK I checked and the bench ESD mat was not grounded (clip fell off), yet soldering stations grounded

ESD usually kills an IC right away or in 2 weeks. The chip arrived in cheapola styrofoam so who knows. I shouldn't fault the disti here.


Increased clock speed from 100kHz to 200kHz and a bit too fast.
I think 150kHz (3 updates/sec) is the sweet spot. Just have to decrease integrating resistor to keep noise low.

[stj]

Re: SICSTOCK chinese semi franchise - opinions?

post/link the datasheets pls.

[redwire]

Re: SICSTOCK chinese semi franchise - opinions?

Original Intersil ICL7135 datasheet

Teledyne (Microchip) TC835 datasheet (part that died).

[eccerr0r]

Re: SICSTOCK chinese semi franchise - opinions?

I hope the vendor didn't use non-esd polystyrene?

That stuff picks up static fast.

[stj]

Re: SICSTOCK chinese semi franchise - opinions?

different circuit on pins 4,5 &6

[eccerr0r]

Re: SICSTOCK chinese semi franchise - opinions?

Yeah the diode and resistor isn't needed for the TC835, but that leaks about 50µA or so, not enough to damage anything; at most it would cause some inaccuracy.

Dangit, still tempted to turbocharge my multimeter...
I'm just kind of worried it'd be too fast for the LCD and the faster update would be wasted.