XO 1.75 A3 ECOs

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These are recommended engineering change orders (ECOs) to the A3 prototype of the XO-1.75 laptop. This is NOT a list of changes from A3 to B1, that is located elsewhere.

SMBus Pullups

These correct a mistake omitting the pullup resistors for the SMBus between the EC and the battery charger. It has been done to all boards.

  • Add a 1.3K resistor between PR200 and +3.3VSUS (available at PD31, pin 2).
  • Add a 1.3K resistor between PR201 and +3.3VSUS.

External SD Power

This corrects a wiring error. It has been done to all boards.

  • Tie PQ64.2 to Q22.2

Audio Power

This corrects a wiring mistake (Trac ticket 10974).

  • Wire +3.3VA_AUDIO (U24.5) to +3.3V_AVDD (the side of C218 closest to the codec).

It has not been done to many boards. Marked AUDIO on the tag.

RTC Power

This corrects the inability of the RTC to maintain data scross a power-off (Trac ticket 10999).

  • Change R29 (top side of board, underneath the RTC) to 330 ohms
  • Add a 10 uF capacitor in parallel with C227

It has not been done to many boards. Marked RTC on the tag.

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