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jwise / x1-expander

Expander board for Bambu Lab X1 Carbon
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X1P-002: 5V buck to 3A #60

Closed jwise closed 1 month ago

jwise commented 1 month ago

blocks #58

jwise commented 1 month ago

Selected Silergy SY8205FCC (LCSC #C111875) -- good efficiency, 500 kHz. Built in OCP is only to save the regulator so needs input OCP/polyfuse (check DCR!) and also needs active OCP on user-accessible 5V and 3V3.

Inductor requirement is for L >= 6.6 uH, Isat > 3.5A (for 3A input). Datasheet suggests DCR < 10 mOhm, but that is hard to come by. CYA1040-6.8UH (LCSC C6364676, second source C7502775) seems good, DCR = 22 mOhm, Isat = 10A. Also acceptable is current package 6.8 uH equivalent, CYA0630-6.8UH (LCSC 5189749) at 50 mOhm DCR, Idc = 4A, Isat = 6.3A. Inductance on both is +/- 20% but regulator d/s indicates that "SY8205 is quite tolerant of different ripple current amplitude".

Same reg can be reused for 5V -> 3.3V.

jwise commented 1 month ago

Reg D/S indicates 47 uF X5R on output and 10 uF X5R on input.

jwise commented 1 month ago

layout complete, released in x1p-002-c01