XO1.5 1.2VSUS power sequencing ECO

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Revision as of 01:18, 17 July 2009 by Wad (talk | contribs) (New page: =Scope= This describes a change to early prototypes of the XO-1.5 motherboard. It fixes a problem with the sequencing of power supply turn-on to the VX855 chip, which preve...)
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Scope

This describes a change to early prototypes of the XO-1.5 motherboard. It fixes a problem with the sequencing of power supply turn-on to the VX855 chip, which prevents power up. Boards having this problem will occasionally fail to turn on, indicated by the EC flashing the red battery charge LED.

These power issues are not exacerbated by suspend/resume testing.

This only applies to XO-1.5 A-phase (both A1 and A2) motherboards.

Problem Description

Procedure

  1. Cut trace between PU5, pin 3 and Vin (keeping PC54 connected to pin 3).
  2. Run wire from PU5, pin 3 to 3VPCU
  3. Cut trace at top of PR70, and tie to +5VSUS
  4. Lift Q22, pin 1 emitter, removing it from the VR_ON net. Tie Q22, pin 1 to +1.2VSUS_GD (PU5, pin 1 or PR70).
  5. Replace PR6 with a 56.2K resistor
  6. Add a 0.1 uF capacitor from PU1, pin 11 (PR6) to ground

Results

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