Chapter 3 — Theory of Operation
CV30 Fixed Mount Computer Service Manual 57
Detection Circuit
There are two detection circuits that respond to special situations in the
power system.
• Battery Fault Detect. In the event that the external supply power drops
below the voltage level of 8 VDC the system detects this and performs
the following:
• Battery charging circuit is disabled.
• MAIN_PWR source is from BK_PWR.
• PIC is notified of power loss.
• Main processor is interrupted with nBATT_FAULT_DET to
complete all necessary tasks and assert the SYS_EN to turn off
certain power planes as detailed in the Power Plane Status table on
page 56.
• Battery Low Power Detect. The Low Battery Detect circuit is used to
notify the system that the backup battery has been discharged to the
critical low level. This voltage level is monitor by the Audio Codec IC
through the BACK_PWR_MONITOR line. The Amber LED will
light up to alert the user to change the backup battery.
Power Routing Circuit
Several power routing circuits are implemented to allow portions of the
CV30 to be powered ON or OFF under software control as needed. These
parts that can be powered ON or OFF include:
•LCD
• Bluetooth Radio
• SD card slot
• Codec (both analog and digital portions)
• Loud speaker amp
• Serial COM power
• USB power
• Ethernet power
• Battery charger
• Processor core power
•WLAN power
• LCD backlight
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