Post History
I'm trying to modify a LED torch, and there is a DC-DC booster (1.5 V to 3.3 V) and after that some SOT-23 device which (I assume) keeps constant 90 mA current through LED. I know I could remove th...
#4: Post edited
by
Lorenzo Donati
·
2023-08-09T19:09:05Z (over 1 year ago)
Retagged.
#3: Post edited
by
Chupacabras
·
2021-02-12T19:18:12Z (almost 4 years ago)
- I'm trying to modify a LED torch, and there is a DC-DC booster (1.5 V to 3.3 V) and after that some SOT-23 device which (I assume) keeps constant 90 mA current through LED. I know I could remove that device and replace it with a resistor, but that has disadvantage that current won't be as stable with temperature drift of LED.
- So I would like to replace that current limiting device for another one.
- I was looking for devices like "[SOT-23 LED constant current driver](https://www.google.com/search?client=firefox-b-d&q=SOT-23+LED+constant+current+driver)", "[SOT-23 constant current regulator](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+regulator)", "[SOT-23 constant current sink](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+sink)", etc. but with no luck finding similar device whatsoever. I couldn't find anything similar on Mouser or Digikey (I could be looking in wrong categories though)
- My question is:
- Is that common device and what is it's name?
- This is the schematic:
- I'm trying to modify a LED torch, and there is a DC-DC booster (1.5 V to 3.3 V) and after that some SOT-23 device which (I assume) keeps constant 90 mA current through LED. I know I could remove that device and replace it with a resistor, but that has disadvantage that current won't be as stable with temperature drift of LED.
- So I would like to replace that current limiting device for another one.
- I was looking for devices like "[SOT-23 LED constant current driver](https://www.google.com/search?client=firefox-b-d&q=SOT-23+LED+constant+current+driver)", "[SOT-23 constant current regulator](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+regulator)", "[SOT-23 constant current sink](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+sink)", etc. but with no luck finding similar device whatsoever. I couldn't find anything similar on Mouser or Digikey (I could be looking in wrong categories though)
- My question is:
- Is that common device and what is it's name?
- This is the schematic:
- 
- **UPDATE:**
- I do not think it is absolutely necessary, but I'm adding full schematic (reverse engineered):
- 
- This is photo of the board:
- 
- SMD codes are:
- U1; DC-DC booster: LahFb (it seems to be YX2118, some chinesium)
- U2; current regulator: IaiHb (or laiHb)
- 
- 
#2: Post edited
by
Lundin
·
2021-02-05T14:58:02Z (almost 4 years ago)
Name of this current limiting device
I'm trying to modify a LED torch, and there is a DC-DC booster (1.5 V to 3.3 V) and after that some SOT-23 device which (I assume) keeps constant 90 mA current through LED. I know I could remove that device and replace it with a resistor, but that has disadvantage that current won't be as stable with temperature drift of LED. So I would like to replace that current limiting device for another one. I was looking for devices like "[SOT-23 LED constant current driver](https://www.google.com/search?client=firefox-b-d&q=SOT-23+LED+constant+current+driver)", "[SOT-23 constant current regulator](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+regulator)", "[SOT-23 constant current sink](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+sink)", etc. but with no luck finding similar device whatsoever. I couldn't find anything similar on Mouser or Digikey (I could be looking in wrong categories though) My question is: Is that common device and what is it's name? This is the schematic: 
#1: Initial revision
by
Chupacabras
·
2021-02-05T10:00:21Z (almost 4 years ago)
Name of this current limiting device
I'm trying to modify a LED torch, and there is a DC-DC booster (1.5 V to 3.3 V) and after that some SOT-23 device which (I assume) keeps constant 90 mA current through LED. I know I could remove that device and replace it with a resistor, but that has disadvantage that current won't be as stable with temperature drift of LED. So I would like to replace that current limiting device for another one. I was looking for devices like "[SOT-23 LED constant current driver](https://www.google.com/search?client=firefox-b-d&q=SOT-23+LED+constant+current+driver)", "[SOT-23 constant current regulator](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+regulator)", "[SOT-23 constant current sink](https://www.google.com/search?client=firefox-b-d&q=SOT-23+constant+current+sink)", etc. but with no luck finding similar device whatsoever. I couldn't find anything similar on Mouser or Digikey (I could be looking in wrong categories though) My question is: Is that common device and what is it's name? This is the schematic: 