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oskirby / logicbone

Logicbone ECP5 Development Board
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Bad part choices (prototype run) #3

Open oskirby opened 4 years ago

oskirby commented 4 years ago

This issue is mostly just to keep a list of parts that we might want to change out if we get a chance.

Designators Part Issue
IC7 FPF2595 0.4mm pitch CSP package is a little too fine. Our stencil manufacturer has raised concerns about yield.
L4, L2 0805 Inductor High current inductors for VCORE and VDDR are a little hard to source in this size. Suggest using a larger footprint to increase options and reduce cost.
RN1, RN2, RN3 EXB-D10C470J Panasonic seems to be the only vendor for this particular footprint, which might lead to supply issues for future production runs. The 2x5 pin rectangular arrangement seems to be more common.
oskirby commented 4 years ago
Another comment from the CM is that the XDFN regulators are a pain in the butt, and should be substituted with a larger and less ambiguous part (such as a TSOP-5). Designators Part Issue
IC17, IC18 NCP110AMX110TBG This part is way smaller than it needs to be, and the KiCAD libraries for the XDFN4 package don't make it very obvious about where pin 1 is.
IC19, IC20 NCP115AMX250TCG This part is way smaller than it needs to be, and the KiCAD libraries for the XDFN4 package don't make it very obvious about where pin 1 is.
oskirby commented 4 years ago

While we're at it, the PGOOD LED (D1) is way too bright and we should increase its inline resistance (R10). To avoid adding another line item to the BOM, the next value of resistance to try would be 750 ohm.

oskirby commented 4 years ago

After a quick bodge, it seems that 750ohm still leaves the green LED in D1 too bright, but the red LED is about right. I think the whole circuit around D1 should be rethought either into discrete LEDs, or to add another resistor tune the drive strength of red and green separately.