Date
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- Now responsible for ESD/overcurrent/reverse-polarity protection on the module.
- Overcurrent protection is to be accomplished by a polyfuse (aka PTC or self-healing fuse) in series with a standard fast-blow fuse on each power rail, appropriately sized to the expected load of the module. Polyfuse should be rated to trip before the other fuse.
- Reverse polarity protection is to be accomplished with a low-resistance FET. See Texas Instruments SLVA139 Figure 3 (Link) for more details.
- ESD protection at a minimum on all out-of-board connectors, preferably also including internal-to-board protections.
- Mentioned multi-channel WSON EMI filter with ESD protection: TPD8F003DQDR (Datasheet)Another more in stock option: TPD4E05U06DQAR (C138714) (Datasheet)
- To further mitigate short/shock risk, where possible replace male headers with shrouded female headers
- For further information on protecting data/signal lines from ESD, see Texas Instrument's 2022 System-Level ESD Protection Guide (Link)
- All modules using Vbat must design to withstand battery voltages up to 12v
- LEDs on the backplane (interfaced through 30-pin connector) are to be operated at 3.3v, although they are 5v tolerant.
- Any LEDs on the module (including those for ethernet) must be toggleable by the module's MCU. Recommend using Vishay SI2301CDS-T1-GE3 (Link)
- Modules are advised to take any other ground-exclusive, high-load components and place them on switching as well, to be deactivated when the umbilical is removed.
- Modules must be designed so that they can be assembled using JLCPCB's single-sided, "Economic" assembly option
- In addition to one-sided assembly, places some restrictions on minimum pin spacing, package type, etc.
- Minimum Package: 0402
- Minimum IC Pin Spacing: 0.5mm
- Minimum BGA Spacing: 0.4mm
- Any parts not available for economic PCB will be marked as such on JLC's part library.
- No through-hole components should be assembled by JLCPCB
- https://jlcpcb.com/capabilities/pcb-assembly-capabilities
- In addition to one-sided assembly, places some restrictions on minimum pin spacing, package type, etc.
- Any programming resistors (such as those used on Ethernet) need to be assembled in a way that the module ships in a determinate, ready-to-use configuration
- In other words, do not have both a pull-up and a pull-down resistor on the same pin
All modules will have an STM32 GPIO check in the near future, to ensure the proper pins are being used for certain signals
- The software team requests, if possible, putting the Wiznet and the memory IC on 2 different SPI busses
- Multiple i2C busses can be used for ease of routing if desired
Battery protection circuitry, as well as the power changeover circuitry, is now moved to the backplane.
- This potentially includes a battery protection IC. See XB8089D as a 1S reference (Datasheet)
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