17
REMOTE
TAS1020B
USB Controller and
Microprocessor
5V 3.3V
WM8772 or AK4626
CODEC
o
D
DACs
ADCs
TI DSP
TMS320DA710
3.3V 1.2V
Audio clock
master
Audio clock
slave
Audio clock
slave
McASPs
EEPROM
I2C Bus
EEPROM
I2C Bus
RAMP
GENERATOR
TOUCH
SENSOR
Bass Knob
Thermistor
MUTE
Volume
Headphone
Aux In
USB Input
3.3V
VRAW
Thermistor
113 115 116
120 119
RT6307
RT6206
Q6101
135
131
134
U7000
27
28
25
23
26
24
9
6
D-
D+
5V
38
26
25
7
6
U6000
U4000
Q6202
Q6203
Audio Path
U1000
Out to
Amplifier
31
138
BADDATA
30
127
DSPINT
122
126
CCLIP
BSCLIP
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.
Audio Path
