BAV99 in KiCAD and other AFE4400 / Morpheus Updates

[ KiCAD library format ]

It turns out that KiCAD has a library component for BAV99, but its hard to tell which diode goes to which pin (Unit A or Unit B?) However, the easy fix is to edit one letter in the corresponding library file for enabling pin numbers for this component!

BAV99

With special thanks to TI’s [ eval board ] and the people at [ pulsesensor.com ], here’s the AFE4400 schematic we have so far:

[ Morpheus AFE4400 RevA1 ]

Notes on design choices and things-to-do:

  • Footprints and Mouser part numbers identified for all Rs, Cs, ESD diodes, and the crystal
    • I suggest we go with a somewhat big (easier to solder!) SMD package size for all Rs and Cs: [ 1206 ], as we are not really space constrained at the moment
    • The ESD diodes were slightly trickier to identify, but now we’ll now go with [ BAV99-7-F ]. This has two diodes per package, and that’s what TI has on its eval board.
  • A [ QFN40 footprint | PN532DS ] has been identified for the AFE4400, but its not a 100% match. We might just make a new one.
  • Payne and I have decided to not deal with power management in our first iteration. We’ll just hook up well regulated supplies for now.
  • Photodetetor (PD) still needs to be identified. Our last decision was to go with an Avago chip [ APDS 9008 ], but since AFE4400 already has signal conditioning circuitry built-in for the PD, I am not sure if APDS 9008 will be a good match.
  • Green (530 nm) LEDs still need to be identified. Our original plan of going with some really reverse mount packages by [Kingbright ] might have to be altered, as they haven’t responded to our sample request yet. We might just have to go with options already in stock at Mouser (the one we were looking at is out of stock.)
  • Layout pending until PD, LEDs, footprints are identified. An additional shielding trace will be used to surround the PD traces (see pin VCM in schematic)

LED/PD choices, VQFN footprint for KiCAD, and eval board layout files coming soon!

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s