The [On Semi NSI45020T1G](https://www.onsemi.com/pdf/datasheet/nsi45020-d.pdf), a simple two-terminal inline current regulator, claims in at least two places that it "turns on immediately". However,

1. it cites a capacitance between 2.5 and 2.7 pF. If that capacitance is modelled in parallel with the device, won't there be a (brief) charge-up period where the current surges beyond 20 mA?
2. Figure 5:

[![Current regulation vs. time](https://i.stack.imgur.com/piyBj.png)](https://i.stack.imgur.com/piyBj.png)

shows that it might not stabilise for over ten seconds!

This concerns me because I'm considering whether to include this in the arm of a PWM-dimmed LED driver:

![schematic](https://i.stack.imgur.com/SN7Px.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fSN7Px.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)

Will the current source be too slow, or introduce unwanted transients during PWM? The 7-segment display claims an absolute max of 25 mA and doesn't distinguish between peak and continuous.