fake ref5050s - Page 1
Forum section: electronics / projects

author: ralphd
author_rank: Frequent Contributor
timestamp: November 11, 2015, 01:08:03 am
content: I thought I had found a good deal for precision voltage references, but I think what I received are fakes.http://www.aliexpress.com/item/REF5050IDGKR-R50F-TI-VSSOP-8-absolutely-new-original-quality-assurance-FREE-Shipping/32327854830.htmlThe markings on the chips look OK (TI2A R50F), but without a cap on the trim/nr pin the output isn't anywhere near 5V (around 4.5V). The power consumption with no load on Vout is around 6mA, while the TI datasheet says it should be 0.8mA.http://www.ti.com/lit/ds/symlink/ref5040.pdfWith a .1uF cap on the trim/nr pin, I get 4.988 (using a $50 DMM), but I highly doubt it's really within .05% of 5V.I'm thinking about trying some LM4040's, but would like to make sure they are genuine...http://www.aliexpress.com/item/LM4040AIM3X-2-5V-LM4040-2-5V-SMD-Voltage-Jizhun-Si-Indian-R2A-SOT-23-SDQYS/32465209684.html

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 11, 2015, 01:18:38 am
content: Hi,Do you have the required capacitors on the REF5050 circuit? The datasheet says 1 to 10uF on the input and 1 to 50uF on the output. On the input they say less than 1.5 Ohms ESR, on the output they say 1 to 1.5 Ohm ESR minimizes the noise.The current consumption could be high because the part is oscillating.Regards,Jay_Diddy_B

author: ralphd
author_rank: Frequent Contributor
timestamp: November 11, 2015, 01:28:42 am
content: I was using a 100uF electrolytic on Vout, and a 220nF ceramic on input. I didn't think it would be that sensitive to the choice of capacitors, so just in case I'll try a > 1uF electrolytic on the input side.

author: ralphd
author_rank: Frequent Contributor
timestamp: November 11, 2015, 03:00:45 am
content: Quote from: Jay_Diddy_B on November 11, 2015, 01:18:38 amThanks for the suggestion. I tried with 2uF electrolytic caps on the input and output, and still was seeing high current consumption. After booting up the Rigol, I was seeing ~600mV! oscillations on the output (input was perfectly stable). The oscillations were rather high frequency, with a period of ~1.5uS. Adding a 220nF ceramic cap stabilized the output. Removing the 2uF electrolytic so there was only 220nF on the output still kept the output stable. Power consumption dropped to .85uA, which is pretty close to the datasheet spec.When I measure the output with my meter I'm getting 5.033V, which seems too high. My meter is new (purchased this year) and is spec'd for 0.3% accuracy on voltage readings. If the ref505 is 0.05% high, the meter would be reading 0.6% high. My previous accuracy tests on the meter suggests it reads 0.1-0.2% high, so I still think the REF5050 isn't good.Maybe genuine TI, but factory rejects sold on the grey market?

author: tron9000
author_rank: Frequent Contributor
timestamp: November 11, 2015, 09:19:17 am
content: Quote from: ralphd on November 11, 2015, 03:00:45 amlooks like it, if the photo's are anything to go by, you can see the ragged edges left on the plastic moulding - definitely grounds for a rejection on production line

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 11, 2015, 12:58:36 pm
content: I love how people always ask "are these real?" and the link is at AliExpress.Every. Single. Time.Tim

author: Sbampato12
author_rank: Regular Contributor
timestamp: November 11, 2015, 01:22:54 pm
content: Never forget the second commandment:"Thou shall never buy precision parts from AliExpress/Ebay"

author: kripton2035
author_rank: Super Contributor
timestamp: November 11, 2015, 01:53:46 pm
content: Quote from: Sbampato12 on November 11, 2015, 01:22:54 pmwhat is the first commandment ?

author: Fungus
author_rank: Super Contributor
timestamp: November 11, 2015, 02:53:27 pm
content: Quote from: Sbampato12 on November 11, 2015, 01:22:54 pmHe's doing it again...!https://www.eevblog.com/forum/testgear/$5-ad584-voltage-references/

author: Sbampato12
author_rank: Regular Contributor
timestamp: November 11, 2015, 03:54:01 pm
content: Quote from: kripton2035 on November 11, 2015, 01:53:46 pm"Thou shall never work at high voltages on barefoot"

author: Fungus
author_rank: Super Contributor
timestamp: November 11, 2015, 05:30:35 pm
content: Quote from: kripton2035 on November 11, 2015, 01:53:46 pmKeep one hand in your pocket.

author: retrolefty
author_rank: Super Contributor
timestamp: November 11, 2015, 05:31:39 pm
content: Quote from: Fungus on November 11, 2015, 05:30:35 pmDon't solder when wearing shorts.

author: splin
author_rank: Frequent Contributor
timestamp: November 11, 2015, 05:46:22 pm
content: Quote from: retrolefty on November 11, 2015, 05:31:39 pmDon't solder when not wearing shorts.

author: SeanB
author_rank: Super Contributor
timestamp: November 11, 2015, 06:46:22 pm
content: Quote from: splin on November 11, 2015, 05:46:22 pmRemember which end of the soldering iron is the cool part......

author: retrolefty
author_rank: Super Contributor
timestamp: November 11, 2015, 06:49:18 pm
content: QuoteI only did that wrong once. Some of the best of life's lessons have to be experienced first hand to be appreciated.

author: technix
author_rank: Super Contributor
timestamp: November 13, 2015, 11:22:06 am
content: Quote from: T3sl4co1l on November 11, 2015, 12:58:36 pmOuch, man, as a Chinese where AliExpress originated from... Although I have to ask the same (and I did ask it here for once) from time to time when buying parts from Taobao (the domestic version of AliExpress) and in China those reputable distributors like element14 and Mouser are newcomers in market and does not even have a chance against Taobao for now.

author: The Magic Rabbit
author_rank: Regular Contributor
timestamp: November 16, 2015, 02:01:44 am
content: I bought two 12V 5A power supplies from AliExpress. One actually exploded while in use, blowing the casing open. Never again.

author: Macbeth
author_rank: Super Contributor
timestamp: November 16, 2015, 02:36:13 am
content: It's odd that people blame AliExpress rather than the seller, but probably don't consider the same for ebay. It's a marketplace. I have to admit I have far more hassle on AliEx than on ebay, but I do go looking for it - I mean trying to get a pair of LTZ1000's for sweet feck all?I got a full refund.I demanded a 33% refund on a $3 pot of solder paste because it was shortI got it.I've not had any trouble with AliExpress refunding me, though they do take their time.My latest is an idiot who advertised a 5V->12V boost converter for £3 delivered, but then tells me he has no stock, and asks me to cancel the order - "buyer no longer wants". I refused, stating "buyer still wants - seller has no stock". Back and forth 3 times. Why he doesn't want Ali to know he has no stock I don't know, but I am not going to lie. It seems he has now "shipped" the item at least electronically but with no collection. I don't know what the imbecile is up to, but it seems like he is digging his own AliExpress grave. I guess I will have to wait 30 days for my £3 to be returned (AliExpress holds money in escrow).Oh, I've had plenty of Ali orders that go through flawlessly, better tracking than ebay from China. it's the idiot ones that amuse me and they always are low valueTaobao is something I would really like to deal with - but I need a forwarder and a Chinese friend I think