XO1.75 C1 C2 Changes

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These are the changes between the XO-1.75 C2 model and the C1 prototypes.

C2 Electrical Fixes

Keyboard/Touchpad

The resistor connecting the EC to the keyboard/touchpad (R351-R354) are populated, fixing <trac>11401</trac> (ECO)

SD Cards

The series termination resistors on the clock line were tuned to 33 ohms.

Speakers

An RC filter was added at the output of the speaker amp to minimize ringing in the speaker traces (but not populated).

ESD

• The protection on the headphone jack was changed from diodes (to GND/+3.3V) to a dual TVS to ground.
• A 100 pF cap to ground was added on the internal Mic input.

DDR3 Suspend Power

• Separate the DDR3 termination power control so that the S3 and S5 states can be independently controlled, and wire the S3 control to VCXO_EN.
• Separately switch the termination power for the DDR3 control lines from the termination power for the DDR3 address lines, to save over 100 mW when suspended. This power saving feature is not populated in SKU203 laptops, but will be in all production laptops.

C2 Layout Fixes

Internal SD

One of the internal microSD socket footprints (CN25) was moved, to avoid the shorting seen in C1.

OLS

A dual LED (with the disk activity LED) is used to minimize damage to the OLS LED due to proximity to the edge of the board.

Speakers

The speaker traces were tuned.

ESD

Additional pins of the external SD card socket were connected to ground.

Production Changes

Many zero ohm resistors were replaced with shorts.

Planned Feature Changes

None.