13
Miscellaneous Control
Power management is affected by controlling the pins for SENSOR, VRAWON, and DSPRESET\.
SENSOR is controlled by U6000.26, which is inverted in logic level from SENSOR. The function of SENSOR is
explained in section 2.7.
The signal VRAWON (U6000.42 enables both the pre-regulator circuit for Vraw and the +10V power supply as
explained in sections 2.1 and 2.2, respectively. VRAWON is active when the USB controller is held in reset. The
USB controller must complete the boot cycle, enable the DSP controller to boot, and monitor the USB interface
and AUX input signal amplitudes. Only if the USB interface is not active (suspended or disconnected) and if the
signal level of the AUX input is less than -70dB and both conditions have persisted for at least 2 minutes, will the
system be placed into stand-by and VRAWON driven low.
DSPRESET\ is an active low signal driven by pin 41 of U6000. This pin is active low at initial application of power
to U6000, keeping the DSP in reset until U6000 has completed initialization. The signal is then negated (high).
The USB controller will reset the DSP just prior to entering stand-by mode of operation.
Transistor Q6101 inverts the MUTE\ signal from the control module to buffer and generate the MUTE signal to
the USB controller (U6000.26). If the mute signal is not present shortly after the USB controller is initialized, the
controller must assume that the control module is not present and command the DSP to enable the speakers,
speaker EQ and set the system volume to full.
At any time the mute signal is present the USB controller
commands the DSP to mute the speaker EQ, mute the speaker Power Amplifiers, and ramp in the headphone
(flat) EQ.
USB Controller
To Power
Supply
To DSP
Pin 14
To I/O Board
Miscellaneous Control
