Open, low-cost experimentation board for the LTC3331 energy harvesting chip
This project contains design- and production-files for a low-cost LTC3331 energy harvesting development-, breakout- and test-board.
It's specifically designed to be inexpensive, yet open and comprehensive:
- Full design files for KiCad EDA
- 10cm x 10cm PCB with 2 layers
- Full pin breakout
- Less-comprehensive headers for pins usually required
- LIR2032 holder and alternative battery port
- All default options can be jumpered on or off
- Supercap pads provided
(Above: v0.1, image rendered by KiCad EDA)
(Above: v0.1, actual photo of both sides)
Releases and History
All production files for releases can be found in the production/ directory. All required production files for PCB production should be zipped in a way that allows immediate upload to your preferred online PCB manufacturer.
v0.1 is the first version of the PCB. It has a few minor issues (see Errata), but is fine for testing.
v0.1 works fine, but there are a few issues that should be addressed for another release:
jumper for BBIN-BATIN connection is not needed.
scatter more GND connectors for oscilloscope use
maybe provide circuit for higher current charging, as seen in datasheet figure 7, pg 27?
extra small header for GND/AC1/AC2/VIN
footprints for 22uF inductors on bottom layer are way too large. a Taiyo-Yuden NR-30xx handsoldering footprint would be fine and should be moved to the front side. then there would be no components on the bottom.
replace all capacitance footprints >= 10uF with larger footprint for e.g. tantalum capacitor.
make cap footprints dual-use: through-hole AND smd?
PCB Placement / Routing:
- reorder all selection jumpers so they comply the the datasheet table
mark down input voltage limits (3-19V)
add white box for charge-current-resistor value placed by user
if enough place, print cap values (and voltage ratings?)
- pdf schematic was missing in release files (was added later). next release should contain that immediately.
Prior Art and Alternatives
Please note: personally I did not obtain any of the following alternatives, so any comparison is a rough guess.
DC2151A is the de-facto standard demo- and dev-board that Linear Technology created for this chip. However, it's really expensive. (200+ €/$)
The "LTC3331 Energy Harvester, DC Converter and Charger" by Blue Spark Labs is a much cheaper alternative to the official dev-board. But it seemingly does not offer comprehensive access to all pins and full breakout options. Also, worldwide shipping can be quite expensive, it seems.
When you want to use or modify the design in KiCad, you should get used to handling git-submodules. I keep my custom footprints and symbols in a separate repository so I can re-use them.
If you have design improvements, find it useful or stupid, or want to let me know anything else, just let me know ;).
The design is released under the OSHW 1.0 license as defined by [https://www.oshwa.org/definition/].