I'm looking for a LED current sink solution with small overall size and reasonable cost to be used in a portable bar code scanner application.
The current solution is built around a LMV931, a reference source and a discrete FET. The current solution has an initial operating point that is set with a potentiometer and then adjusted by a small current feedback from the LED as it ages to maintain constant brightness. The reference source is no longer accurate or stable enough giving us an opportunity to displace the entire solution. The LED current will be about 40mA full scale. The exact current is production set according to a set level of brightness. Ideally they could automate this process, but that trade off will be weighed against the added size/cost of the pot.
Looking for any ideas at this point.
What is the diode Vf and VCC input range and what is sense and adjustment method as it ages?
The diode datasheet is attached. It has a small signal that is feedback to be used for adjustment. As the diode ages the light decreases for a given current. This decrease is detected in the amount of light that is feedback resulting in a decrease in current being feedback. This signal is used to increase the forward diode current. Vcc is 3.3V +/- 3%.
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