Suggest/Identify IC that voltage regulates with on/off switch? - Page 1
Forum section: electronics / projects

author: RL_Tracksuit_Electro
author_rank: Contributor
timestamp: March 22, 2021, 01:52:58 pm
content: I recently repaired a pcb, that in the end just needed some contacts cleaned. But in the initial assessment/analysis I came across a 6-pin IC that seemed to do the following:1. Regulate dc voltage to 1/2 input voltage, specifically I tested 6v and 3v, which resulted in output of 3v and 1.5v respectively.2. Via a moment switch toggle output voltage on and off. So I assume debounce built into the IC, though3. there is a small smd passive accompanying the ic, but my cheapo identifier can't decide if it's a diode or a capacitor, but I suspect likely a cap.I could see this being really useful in future projects. It is stamped with 04PK. I'm not too concerned with specifically identifying it, would be happy to hear of alternative ICs that can do the same functions (regulate voltage and serve as on/off with moment switch all in one small package).Thanks

author: bob91343
author_rank: Super Contributor
timestamp: March 22, 2021, 11:59:27 pm
content: It would seem that such a simple function could be designed and built easily from standard components, such as a regulator.

author: amyk
author_rank: Super Contributor
timestamp: March 23, 2021, 12:36:31 am
content: That's probably a PIC10F204. What's the pinout?

author: RL_Tracksuit_Electro
author_rank: Contributor
timestamp: March 23, 2021, 01:41:16 am
content: Quote from: amyk on March 23, 2021, 12:36:31 amNever occurred to me it would be a microcontroller.Unfortunately I didn't map all the pins before I reassembled it all and gave it back to the owner.The device is a laser pointer. I did not measure the current draw with the laser operational, and admit I'm completely ignorant about what current a typical red consumer laser pointer draws. So one question would be if that pic can handle the current, not sure I understand the spec sheet correctly as to whether 25ma, 75ma or 80ma. Owner told me the device is about 10 years old, and the copyright on the spec sheet is within that range.

author: wizard69
author_rank: Super Contributor
timestamp: March 23, 2021, 07:34:41 pm
content: It could be a regulator of some sort with an enable pin. This would require a pushbutton that toggles between states, it wasn't clear if this was happening here. Even then I'm not sure if we can even call it a regulator if it only divides the input voltage by two. So the question becomes is there voltage regulation going on or is it a voltage divider.OnSemi has a TN on using their approach to an enable:https://www.onsemi.com/pub/Collateral/AND8239-D.PDFbut this doesn't sound like the approach you are describing. Most of the enables I'm familiar with (which isn't many) are just inputs to analog comparators. That is nothing digital to flip states. That doesn't mean that such regulators don't exist though.

author: james_s
author_rank: Super Contributor
timestamp: March 23, 2021, 08:09:30 pm
content: It's probably a voltage regulator with an enable pin configured as a constant current source. A variant of the classic LM317 based current regulator I would assume. The fact that it's a laser pointer should give you some clues, since laser diodes require a constant current source.

author: RL_Tracksuit_Electro
author_rank: Contributor
timestamp: March 23, 2021, 08:10:35 pm
content: Quote from: wizard69 on March 23, 2021, 07:34:41 pmI believe the switch here did not have state, because every time I removed and then added back power there would be output voltage, i.e. "on" so it seems like a moment switch and the ic itself is managing state. I started thinking maybe the little cap is used somehow to hold a pin and then the switch drains the cap but that didn't seem likely. Oh well. If the owner ever needs it looked at again maybe I can explore it more.

author: RL_Tracksuit_Electro
author_rank: Contributor
timestamp: March 23, 2021, 08:17:30 pm
content: Quote from: james_s on March 23, 2021, 08:09:30 pmUnfortunately I did not measure output current on a load, just the voltage (which was observed to drop when input voltage dropped).

author: thm_w
author_rank: Super Contributor
timestamp: March 23, 2021, 10:08:47 pm
content: Quote from: amyk on March 23, 2021, 12:36:31 amIt does seem to be:https://ww1.microchip.com/downloads/en/DeviceDoc/40001239F.pdf- Pin 2 is Gnd (going to via)- Pin 5 is Vdd (can't see for sure though)- Silkscreen matches that of some sellers