Psion Teklogix OMNii HDK XT10, Руководство пользователя

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Chapter 6: Omnii Expansion Ports and Connectors
Expansion Port Power
Psion Teklogix Omnii HDK User Manual 91
Figure 6.12 Location of Expansion Port 3 on GPS/WWAN Board
6.4.1 Expansion Port Power
This section describes the power supplies used by the expansion ports, and how to calculate the
power available to an expansion module.
A 3.3 volt power supply is supplied for low power interface logic. This power supply is limited to
100 mA current.
VSYS is an unregulated power supply derived from the battery or from the regulated DC power
supply generated by the AC/DC converter or adaptor powering a docking accessory (referred to as
AC). VSYS is the rail from which the other power supplies are derived. The voltage of VSYS can
vary between 3 volts and 4.2 volts depending on the state of the battery.
Expansion ports 1 and 2 each have switched VSYS (pins 3, 4 and 5) on the connector which
should not be used to draw more than 1000 mA current. Expansion port 3 on the multi-function
connector has one switched VSYS pin (pin 3) limited to 1000 mA, and there are also three
unswitched pins on the same connector (pins 2, 4 and 6) which provide VSYS power up to a
maximum current of 2000 mA. If a GPS module is installed in the multi-function connector,
the 22-pin connector on the back of the module that keeps expansion port 3 exposed and
provides the same power output as expansion ports 1 and 2 (pins 3, 4 and 5 switched VSYS
limited to 1000 mA).
If only one expansion port is being used you can disregard the following current usage
calculations and simply use the values specified by the expansion port pinout table as the
maximum current available for the expansion module.
Although there is no restriction on the simultaneous use of the three expansion ports, the total
amount of power being used by the system must be considered. This includes the Omnii core
electronics, on-board peripherals and any standard options. The following table gives the typical
current drawn from VSYS for each subsystem under given conditions, when VSYS is at a typical
battery voltage of 3.7 V.
Expansion
Port 3
Table 6.4 Subsystem Power Usage
Subsystem Condition Current (mA)
Display (DISP) Maximum brightness 100
Minimum brightness 40
Default brightness 72