Senoko PVT ECO List

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Revision as of 09:03, 7 July 2014 by Bunnie (talk | contribs) (ECO 4: Remove JTAG and replace with test pads)
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This is a list of all the changes applied to the board from DVT to PVT (Crowd Supply initial campaign) release. If it's not on this list, it didn't happen.

Each change has the format of issue summary/resolution, and specific change

ECO 1: Improve inductor clearance

The ferrite MSS1260 used as the primary power inductor is a bit too tall and large. Use a composite molded core XAL7030 which is a bit more compact.

Pros/cons: XAL7030 has a better rated Irms than MSS1260, but seems mostly due to better heat conduction out of the package, not due to better electrical performance. The DCR of XAL7030 is 19.5mOhm, MSS1260 is 12.60mOhm, so conduction losses are greater. Isat of the XAL7030 is better due to soft-saturating characteristic of the composite core. Overall, I expect there to be very little change in practical circuit performance, perhaps a little extra heat during peak battery charging situations.

The MSS1260 isn't removed from the PCB layout. Instead, XAL7030 shall be fitted inside the footprint of the MSS1260. This allows for going back to the original inductor in case there is a design issue with the XAL7030.

This change is coordinated onto Novena BOM as well.

L200 3.3uH, MSS1260-332NL L200 3.3uH, MSS1260-332NL (DNP) remove from BOM but leave footprint
add L200B 3.3uH, XAL7030-332MEC add inductor within old footprint

ECO 2: Route power switch to mainboard

Power switch pin is routed to mainboard for pass-through to front panel.

Pin 14 (previously an NC 3.3V pin) is now dedicated to CHG_PWRSWITCH.

add R120 330, 1% ballast resistor

ECO 3: Add power supply detection hooks

Per xobs' request, a spare ADC and UART TX/RX pin is routed to a test point, to enable auto-detection of power supplies that offer such a feature.

Conveniently, USART2_TX is multiplexed with an ADC inside the STM32. This means we can have one connector to do it all.

P102 is re-purposed from a general analog input to use as an ADC/one-wire interface. In order to make this work, a 4.7k pull-up is added to 3.3V_UC.

The header is also replaced to be a JST-B2B-EH-A type connector, which offers a friction-lock modular solution for wiring, as opposed to the current rather slippery pin header.

add R121 4.7k, 1%
P102 Male 2.4mm 2x1 right angle header P102 JST B2B-EH-A

ECO 4: Remove JTAG and replace with test pads

Remove the JTAG header to make space for other mods. We've never really used it anyways.

P100 Male 2.54mm 10x2 header removed
R115 10k, 1% removed
add several test points, no BOM impact