View source for XO1.75 C1 C2 Changes

{{OLPC}}
These are the changes between the [[XO-1.75]] [[XO_1.75_C2|C2]] model and the [[XO_1.75_C1|C1]] prototypes.

=C2 Electrical Fixes=

==Keyboard/Touchpad==
The resistor connecting the EC to the keyboard/touchpad (R351-R354) are populated, fixing <trac>11401</trac> ([[XO_1.75_C1_ECOs#Loss_of_first_keypress_when_suspended|ECO]])

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

==Speakers==
An RC filter (1 ohm, 6800 pF) was added to each trace at the output of the speaker amp to minimize ringing at the switching frequency in the speaker traces.

==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.

[[Category:Hardware]]
[[Category:XO-1.75]]