I'm looking for a diode with a specific forward voltage (about 1V) when current is around 150mA (though the max current should be around 250mA or higher).
The closest I've come so far is the 1N270 (1V forward voltage around 200mA), and 1N4001 (about 0.7V forward voltage around 150mA). Does anyone know of anything closer to what I want, or know of a way to look them up? DigiKey is overwhelming when I just need something similar to the 1N270.
Thanks for the help!
Apologies for the lack of background. I'm essentially looking for a component that can take a 3.7V nominal LiPo (4.2V when full, 3V when "empty") down to about 2.8-3.6V. I'm trying to power a device that typically runs on 2 AAs in series (3V). It has a bit of tolerance on the voltage. The device has a warning light that comes on at about 2.4V. The device operates at about 150mA on average (though it may range from about 100mA - 250mA).
I would like to avoid the warning light coming on too close to the LiPo's cutoff voltage (3V). I can use a 1N4001, which gives about 0.7V drop on average for my current. I'd like to have slightly more drop (closer to 1V) to give more time for the warning light to show before the battery cuts out (maybe at 3.2V - 3.3V on the LiPo). I know the discharge curves of LiPos get pretty steep towards the end, and I also don't want to push the LiPo too hard by having the user run it down all the way.
To sum up:
- Source (LiPo) is 3.7V nominal, 4.2V when "full", 3.0V when "empty"
- Device runs nominally at 150mA
- Device warning light at about 2.4V (at device)
- Would like 2.4V on device to map to about 3.2V-3.3V on LiPo
- This leads to about 0.8V-0.9V desired voltage drop from LiPo to device
I understand that I can use a resistor, though I wanted something that gave a slightly less current-dependent voltage drop, and the forward voltage curve of the 1N270 and 1N4001 fit the bill fairly closely.
I also understand I can use a 3V regulator, and I've found a good one with low quiescent current. Though that reduces the effectiveness of the device's warning light.
I hope that explanation helps illuminate the purpose.
Big question: There's got to be a better way. What component(s) can I use instead to give a more predictable/consistent voltage drop?
I was originally going to use the 3V MCP1700 LDO regulator(it's got a nice low quiescent current), with 0.18V typical dropout. The problem is that the LiPo will cut off at 3.0V, far above the 2.4V warning voltage... Using the MCP1700 would provide unregulated voltage only for about the 3.0V - 3.18V range. Any ideas?