Audio Path - Bose Companion 5 Service Manual

USB Input
6
D-
U6000
7
D+
TAS1020B
USB Controller and
Microprocessor
25
5V
Audio clock
master
26
Q6101
REMOTE
MUTE
TOUCH
SENSOR
Volume
Aux In
Headphone

Audio Path

The audio path is implemented on McASP1 of the DSP. All clocks are generated by the USB controller, U6000.
The DSP expects audio input from the USB controller on pin U7000.135. The audio input from the CODEC is
expected on U7000.134. The DSP sends audio data to the CODE on pin U7000.131. All other details of the
audio path will be deferred until section 5. The left and right channels of the USB input are summed with the left
and right channels of the AUX input prior to processing the audio stream. The volume control is applied to the
mixed stream. Volume matching the two streams is accomplished by either using the Windows or application
volume control on the connected PC, or by using the volume control available on the device connected the AUX
input.
Miscellaneous I/O
The DSP receives warning of a USB audio data checksum error on the BADDATA input, U7000.138. USBINT\ is
used to signal other errors. It is present on pin U7000.127.The Power Amplifier Clip Detect output are monitored
by the signals CCLIP\ and BSCLIP\ signals on U7000.122 and 126 respectively. The temperature of the DSP
assembly is monitored by the thermistors RT6206 and RT6307. RT6206 is located between power FET Q10 and
rectifier D10, while RT6307 is located near rectifiers D11 and D12. The thermistors are of the positive tempera-
ture coefficient type (PTC) with a nominal resistance of 470 Ohms at 25oC. The resistance of these components
rapidly increases when the temperature is near 105oC. The increase in resistance will increase the base-emitter
voltage on the transistors Q6202 and Q6203 to the point that the transistors will switch to an on state, driving
the DSP inputs U7000.119 and U7000.120 low. When either of these inputs is low, the DSP will reduce the audio
output level by 0.05dB/second for up to 120 seconds. The maximum attenuation is 6dB. When both U7000.119
and U7000.120 are high, the attenuation will be reduced at the same rate until full audio output is again
achieved.
3.3V
38
EEPROM
I2C Bus
31 138
BADDATA
30
127
DSPINT
RAMP
GENERATOR
VRAW
Bass Knob
U1000
Audio Path
EEPROM
3.3V 1.2V
I2C Bus
135
131
McASPs
134
U7000
122
TI DSP
TMS320DA710
126
Audio clock
slave
113 115 116
120 119
Q6202
Q6203
17
5V 3.3V
9 6
CCLIP
27
DACs
ADCs
BSCLIP
28
U4000
WM8772 or AK4626 o 25
CODEC D
23
26
24
Audio clock
slave
Thermistor
RT6307
Thermistor
RT6206
Audio Path
Out to
Amplifier