XO DC Input

This page attempts to detail the different tests that an XO DC power input should pass.

Absolutes

These are static tests of the input protection circuitry:

Valid Input Voltage

The laptop shall operate and charge the battery when supplied with any voltage between 11V and 24V (inclusive).

The laptop shall accept a DC input with an AC ripple component up to 2V (peak-peak), provided that the the peak input voltage never drops below 11V or exceeds 24V.

Overvoltage

The laptop shall not be damaged by the application of voltages up to 40V, for any length of time.

Applying a voltage higher than 40V shall not result in fire, but may destroy the internal fuse.

Undervoltage

The laptop shall not draw power from the DC power input when supplied with voltages between 0V and 9V.

Negative Voltage

The laptop shall not be damaged by the application of a negative voltage up to -38V, for any length of time.

Applying a negative voltage larger than -38V shall not result in fire, but may destroy the internal fuse.

Maximum Power Draw

The laptop shall never draw more than 25 Watts of power from its DC power input. This is usually tested with the laptop on and running processor tests from Open Firmware, while charging a low battery (open circuit battery voltage less than 5.6V).

The actual power limit depends on the laptop model. For XO-1, this number was 17 Watts.

Behavior when plugging/unplugging

Power draw when turned off

The power draw of the laptop from the battery shall not exceed 2 mA when the laptop is turned off and no external power is provided.

Power brownout while charging

The laptop shall tolerate quick interruptions in DC power input without disturbing the battery charging. If must be confirmed that the battery charging continues properly, not just that the indicators indicate that charging is continuing.

Seen as Trac 9983

Suspend/Resume

In general, all tests should operate identically whether or not the laptop is suspended. Historically, we have had some problems in these areas:

Inserting power while suspended

If power is supplied to the DC power input while the laptop is suspended, the laptop should automatically begin powering itself from the external power source. If necessary, the battery should begin charging. All indicators (power and battery LEDs) should properly indicate that external power has been supplied.

Removing power while suspended

If power is removed from the DC power input while the laptop is suspended, the laptop should continue operation from battery. All indicators (power and battery LEDs) should properly indicate this loss of external power.

Seen as Trac 10369

Solar

Traditionally, this is the area where we don't test enough. It is important to realize that if the laptop is using solar power as a source, it is almost always receiving less power than it wants!

Operation from underpowered solar panels

I'm still thinking about this, but I believe that a respectable target is operation with 10 and 30 ohms inserted in series with the power source, with open circuit voltages swept from 10 to 24V (and the reverse) over a period of a minute, with no oscillation.

Multiple laptops sharing a panel

Multiple laptops should be able to share a solar panel which has an adequate power rating.

Error Conditions

Indication of critically low battery

The laptop shall indicate that the battery is critically low by turning on the red battery LED when the laptop is turned on.

Seen as Trac 3610, Trac 5858, and Trac 10033

The laptop shall not indicate the battery status when the laptop is turned off.

Seen as Trac 10668

Inserting power while battery is low

Applying power to the laptop while the battery is low shall not cause the laptop to power off.

Seen as Trac 2182