Please help me to identify this SOP-18 IC - Page 1
Forum section: electronics / beginners

author: ranger81
author_rank: Contributor
timestamp: October 07, 2017, 10:49:24 am
content: Hi,I have a SOP-18 IC (0.65mm pin pitch) which I need to identify. It seems the vendor removed the labels on top of the IC, so I need your help.The IC is usually connected to a bunch of LEDs and two pins are connected to an epoxy blob (I guess a MCU). I assume the IC is some kind of shift register or LED driver, but I would like to know which one exactly. Based on the number of pins and location of the GND and VCC pin I could also assume it's a PIC MCU, but just for controlling LEDs, that would be an overkill imho...Attached I have pictures of the IC top and bottom (with some codes "T6AL7CFF0074-2" and "VO8") and a schematic how to IC is connected on the PCB. Under the IC on the PCB there was the code "8A21" printed on the silkscreen.I hope you can help me to identify this part.Thanks!!Edit:A little bit more information on the device in which the IC is integrated:This devices has 10 LEDS connected to the "unknown" IC. The IC itself is connected with two pins to an epoxy blob which is probably the microcontroller of the circuit, because this blob is also connected by USB to the computer. This is why it's hard for me to believe it's a PIC.I analysed the pins 16 and 13 which are connected to the MCU and I can say, that pin 16 seems to be some kind of Enable pin. As long as this is High, nothing happens on the LED ouputs. If pin 16 is low, signals on Pin 13 seems to be relevant: Pin 13 receives High/low signals depending on how many LEDs should light.For every low signal, another LED will be enabled. If there are no more LOW signals on pin 13, the LEDs will turn off (successively - one after another) - The number of enabled/disabled LEDs will update once every 450ms and only one LED at a time.What's this device all about?The device was originally sold as "typing trainer". It's connected by USB and on the computer there is a small application required to run in the background. For every keystroke you are typing on the keyboard a LOW signal is sent to pin 13 of the IC, telling the IC to turn on a LED. The faster you are typing on the keyboard, the more LEDs will light up. If you are getting slower or stop typing, the LEDs will go off (successively every 450ms).If you need further information, please let me know.

author: amyk
author_rank: Super Contributor
timestamp: October 07, 2017, 05:04:32 pm
content: My best guess is that itisa PIC. Is this in a working device? Perhaps an oscilloscope on pin 16 will reveal more information, since that is CLKIN; if it is a PIC, then you will see a clock signal.

author: wraper
author_rank: Unknown
timestamp: October 07, 2017, 05:19:00 pm
content: Quote from: ranger81 on October 07, 2017, 10:49:24 amWhat those LEDs do display? Isn't it some sort of bargraph by chance?

author: jpanhalt
author_rank: Super Contributor
timestamp: October 07, 2017, 05:56:45 pm
content: Quote from: amyk on October 07, 2017, 05:04:32 pmWhile in 18-pin PIC's Pin 14 is often Vdd and Pin 5 is Vss, it would be unusual to ground MCLR (Pin 4).

author: ranger81
author_rank: Contributor
timestamp: October 07, 2017, 06:26:57 pm
content: A little bit more information on the device in which the IC is integrated:This devices has 10 LEDS connected to the "unknown" IC. The IC itself is connected with two pins to an epoxy blob which is probably the microcontroller of the circuit, because this blob is also connected by USB to the computer. This is why it's hard for me to believe it's a PIC.I analysed the pins 16 and 13 which are connected to the MCU and I can say, that pin 16 seems to be some kind of Enable pin. As long as this is High, nothing happens on the LED ouputs. If pin 16 is low, signals on Pin 13 seems to be relevant: Pin 13 receives High/low signals depending on how many LEDs should light.For every low signal, another LED will be enabled. If there are no more LOW signals on pin 13, the LEDs will turn off (successively - one after another) - The number of enabled/disabled LEDs will update once every 450ms and only one LED at a time.What's this device all about?The device was originally sold as "typing trainer". It's connected by USB and on the computer there is a small application required to run in the background. For every keystroke you are typing on the keyboard a LOW signal is sent to pin 13 of the IC, telling the IC to turn on a LED. The faster you are typing on the keyboard, the more LEDs will light up. If you are getting slower or stop typing, the LEDs will go off (successively every 450ms).If you need further information, please let me know.

author: Bruce Abbott
author_rank: Frequent Contributor
timestamp: October 07, 2017, 06:46:47 pm
content: Quote from: ranger81 on October 07, 2017, 10:49:24 amWhy do you need to identify it?QuoteThe bottom label is laser etched, so the top probably would been too. However the top doesn't appear to have been filed down, so perhaps it never had a label.QuoteDoesn't look like a PIC. Do the LEDs have series resistors?

author: ranger81
author_rank: Contributor
timestamp: October 07, 2017, 07:07:41 pm
content: Quote from: Bruce Abbott on October 07, 2017, 06:46:47 pmBecause I have a lot of pcbs laying around with these chips and before throwing them away, I would like to know if it's worth desoldering them.Quote from: Bruce Abbott on October 07, 2017, 06:46:47 pmAs far as I can see, there is one "big" 1206 120ohm resistor on the common anodes of the leds. But not separate resistors on all LEDs.

author: wraper
author_rank: Unknown
timestamp: October 07, 2017, 11:16:49 pm
content: Quote from: ranger81 on October 07, 2017, 07:07:41 pmThen it is not worth it. Adjusting your circuits to use some obscure crap for which you waste your time and space does not make sense, unless you live in the hole from where you cannot order parts you need. These ICs are not worth more than few tens of cents per piece when new, anyway. And I can ensure you from my past experience that 99,9% of the parts you desolder eventually will end up in trash anyway. And for that 0,1% you'll actually use, you'll waste more time organizing and searching them in piles of trash than just ordering them new.