Sensor And Power Failure Detection - Bose Companion 5 Service Manual

Out to
Control
Pod
Sensor
SENSOR is generated by switching the +3.3 volt supply via Q6102. SENSOR powers the touch sensor in the
control module. switching SENSOR off momentarily forces the control module touch sensor to reset, forcing its
output to the muted state. This is typically performed just prior to entering the stand-by mode of operation. A
subsequent transition from mute to active will cause the system to exit stand-by.
Power Failure Detection
Detection of power failures is accomplished with U6001, a Maxim MAX809 undervoltage detection IC. U6001
directly monitors the +3.3Volt supply which is used by the USB controller, U6000, the DSP I/O circuitry, U7000,
and the CODEC digital circuitry, U4000. In order to prevent an undetected disruption of the DSP due to loss of
the core power supply, the SOFTSTART signal from U50 is used to switch the PNP transistor, Q6000, on
whenever +1.2V has stopped due to undervoltage lockout. Q6000, in turn, removes the +3.3 volts from the
undervoltage detection IC, U6001, forcing a reset of the USB controller.
Sensor and Power Failure Dectection
USB Controller
9