Orchard EVT1 to DVT1

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Revision as of 09:22, 26 April 2015 by Bunnie (talk | contribs) (ECO5: Add USB adapter presence logic)
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ECO1: Fix Microphone mirroring

Microphone schematic symbol was mirrored. No BOM change, board layout change only.

ECO2: Make battery easier and safer to solder

Space battery terminals wider, increase pad size, and add solder mask openings around the battery tabs. This makes it less likely to short wires together during a botched soldering operation.

ECO3: Fix gas gauge topology

Gas gauge goes between the charger and battery, not between the charger and the system. Oops!

ECO4: Add isolation resistors on SPI to OLED

For independent I2C operation of the OLED and complete dedication of the SPI bus to BLE, isolation resistors are needed on SPI1_SCK and SPI1_MOSI to the OLED display.

EVT DVT Notes
added R19D 0 ohm
added R20D 0 ohm

ECO5: Add USB adapter presence logic

There is no reliable way to detect the presence of a USB power source due to the VUSB boost mode supply of the BQ24260 (observing VUSB isn't helpful because BQ24260 supplies it when the USB power is disconnected).

Add a 10k ohm pull-up resistor to USB_P and a 100k pull-down resistor to USB_N. Wire USBD_P and USBD_N via 0-ohm jumpers to spare ADC inputs on the Kinetis-W.

Expected behavior:

  • When no USB host is attached, USB_P goes to 3.0V
  • When a USB host is attached, USB_P is pulled down to somewhere around 2.2V
  • When a USB dedicated charger is atached, USB_P is pulled down to around 2.8V
  • The only failure case is if the charging source does nothing with the D+/D- lines, but that is out of spec.

A software loop will need to sample USB_P and USB_N pins and toggle between boost and charge mode.

EVT DVT Notes
added R29B 10k, 1% pull-up on USB_P
added R31B 100k, 1% pull-down on USB_N
added R17M 0 ohm allow spare ADC input (ADC0_SE12) on Kinetis-W to sample USB_P
added R16M 0 ohm allow spare ADC input (ADC0_SE9) on Kinetis-W to sample USB_N

ECO6: Improve boost ripple performance

Add another 10uF cap on VUSB to improve ripple performance during boost mode.

EVT DVT Notes
added C28B 10uF, 10V X5R