This week’s find is a NSI450xx/NSI500xx family of parts from On Semiconductor. It’s a two terminal constant current regulator (CCR) offered in SOD-123,SOT-223 , SMB, SMC and all the way to DPAK cases. The device can handle 45V surges and regulates current to 15-350 mA depending on the individual part number. This makes it very convenient to insert into LED strings and have them stay in regulation and constant brightness with variable input voltage. Or put one after a rectifier and power a bunch of LEDs from AC source. Other uses are battery charging (you can parallel them for the desired current), or running specific current through contacts to keep them clean. Very simple to use and cheap ($0.22 qty 1k for NSI45030AZT1G)

Some part numbers to look at are:

SOD-123 devices are:
NSI45015WT1G, Steady State IREG = 15 mA±20%
NSI45020T1G, Steady State IREG = 20 mA±15%
NSI45025T1G, Steady State IREG = 25 mA±15%
NSI45030T1G, Steady State IREG = 30 mA±15%
NSI45020AT1G, Steady State IREG = 20 mA±10%
NSI45025AT1G, Steady State IREG = 25 mA±10%
NSI45030AT1G, Steady State IREG = 30 mA±10%
NSI50010YT1G, Steady State IREG = 10 mA±30%

SOT-223 devices are:

NSI45025ZT1G, Steady State IREG = 25 mA±15%
NSI45030ZT1G, Steady State IREG = 30 mA±15%
NSI45025AZT1G, Steady State IREG = 25 mA±10%
NSI45030AZT1G, Steady State IREG = 30 mA±10
NSI45020JZT1G, Adjustable IREG = 20−40 mA±15%
NSI45035JZT1G, Adjustable IREG = 35−70 mA±15%

DPAK devices are:
NSI45060JDT4G, Adjustable IREG = 60−100 mA±15%
NSI45090JDT4G, Adjustable IREG = 90−160 mA±15%
NSI50350ADT4G, Steady State IREG = 350 mA±10%

SMC devices are:
NSI50350AST1G, Steady State IREG = 350 mA±10%

SMB devices are:
NSIC2050BT3G, Vak max = 120V, Steady State IREG =
50 mA±15% (Product Preview)
NSIC2030BT3G, Vak max = 120V, Steady State IREG =
30 mA±15% (Product Preview)
NSIC2020BT3G, Vak max = 120V, Steady State IREG =
20 mA±15% (Product Preview)

SC-74 devices are:
NSI45019JPT1G, Adjustable IREG = 19-35 mA±15%,