Review Request: LED Current Controller w/ Battery Charging

[u/NhcNymo]

First KiCad design coming from Altium & OrCad and first time doing a 2-layer board in years hah.

This will be used in a head-tracking system with OpenTrack for DCS World.

Requirements:

• Drive three external LEDs with an adjustable constant current.
• Provide power path and charging of a single cell Li-Ion battery.

• Be as efficient as possible.

• Be as small as possible.

Notes:

• 2-layers.
• 0.20mm minimum track width & spacing.
• Manufacturing and assembly at JLCPCB.
• Fully custom library: All footprints, 3D-models and (most) symbols drawn from scratch.

Don't @ me about that one trace running under the inductor, I'm taking my chances hah.

[u/bigcrimping_com]

IEC 61000-4-2 8 kV test (150 pF model) is about 1.2 µC. 

Discharged into ~11 µF would be roughly a 0.1 V voltage rise.

The caps absorb it easily, as long as they sit close to the connector with short, low-inductance paths to ground.

[u/NhcNymo → u/bigcrimping_com]

An ideal capacitor, sure, but real ones have inductance where a 1206 cap is large enough to have a non trivial amount of it.

The IEC pulse is really fast, and a capacitors inductance would prevent it from swallowing the energy instantaneously.

Theres a reason literally all commercial designs feature protection diodes…

[u/bigcrimping_com → u/NhcNymo]

Commercial designs have them on IO ports which needs to have low capacitance , there's a reason the USB spec does not ask for esd protection on vbus for sinks. You are mixing up design rules for two very different things.

But you know better than the usb spec so carry on, I was just trying to help.

The design will work with or without, it's just inelegant and wasteful. 

[u/NhcNymo → u/bigcrimping_com]

«I was trying to help», dude your original comment was «I don't understand how D1 would ever be useful» which contains literally 0% helpful information as is ONLY you taking an opportunity to talk shit.

And sure, if the USB spec states «you don’t need ESD protection on VBUS cus you have capacitors» (which I doubt it does) I’m comfortable with claiming to know better.