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TSC2300
SLAS372 — NOVEMBER 2002
Audio Bypass Mode
In audio bypass mode, the L/RLINEIN analog inputs can be routed to mix with the DAC output and play to the
line-outputs (VOUTL/R) as well as the headphone outputs (HPL/R) and mono output (MONO+/-). This path has a
stereo analog volume control associated with it, with range settings from +12.0 dB to -35.5 dB in 0.5-dB steps. If the
audio ADC’s and DAC’s are not used while the bypass path is in use, the ADC’s and DAC should be powered down to
improve noise performance and reduce power consumption.
This analog volume control has soft-stepping logic associated with it, so that when a volume change is made via the
SPI bus, the logic changes the actual volume incrementally, single-stepping the actual volume up or down once every
20 sec until it reaches the desired volume level.
This volume control also has similar algorithms as the ADC/DAC volume controls, in that the volume starts at mute
upon power-up, then is slowly single-stepped up to the desired level. At a power-down request, the volume is slowly
single-stepped down to mute before the circuit is actually powered down.
Differential Monophonic Output (MONO+/-)
The differential mono output of the TSC2300 can be used to drive a power amplifier which drives a low-impedance
speaker. This block can output either a mono mix of the stereo line outputs, or the analog input to the audio ADC. This
is selected through the MONS bit (Bit 2, Reg 04h, Pg 2). The mono mix of the line outputs is represented by the
equation VOUTL/2 + VOUTR/2. Similarly, the mono mix of the analog line inputs is represented by LLINEIN/2 +
RLINEIN/2.
Microphone Bias Voltage (MICBIAS)
The TSC2300 provides an output voltage suitable for biasing an electret microphone capsule. This voltage is always 1
V below the supply voltage of the part. This output can be disabled through the MIBPD bit (Bit 6, Reg 05h, Pg 2) to
reduce power consumption if not used.
Power Consumption
The TSC2300 provides maximum flexibility to the user for control of power consumption. Towards that end, every
section of the TSC2300 audio codec can be independently powered down. The power down status of the different
sections is controlled by Reg 05h in Pg 2. The analog bypass path, headphone amplifier, mono output, stereo DAC,
audio ADC, microphone bias, crystal oscillator, and oscillator clock buffer sections can all be powered down
independently. It is recommended that the end-user power down all unused sections whenever possible in order to
minimize power consumption. Below is a table showing power consumption in different modes of operation.
OPERATING MODE DESCRIPTION
REGISTER 05H BIT VALUES
POWER CONSUMPTION
TYP
UNITS
15
14
13
12
11
10
9
8
6
5
4
STEREO RECORD AND PLAYBACK
Mono record, line playback, 48 kHz
0
1
0
1
0
TBD
mA
Mono record, line playback, 8 kHz
0
1
0
1
0
TBD
mA
Mono record, headphone playback, 48 kHz
0
1
0
1
0
1
0
TBD
mA
Mono record, headphone playback, 8 kHz
0
1
0
1
0
1
0
TBD
mA
STEREO PLAYBACK ONLY
Line playback only, 48 kHz
0
1
0
1
0
TBD
mA
Headphone playback only, 48 kHz
0
1
0
1
0
1
0
TBD
mA
RECORD ONLY
Mono record, 48 kHz
0
1
0
1
0
TBD
mA
Mono record only, 8 kHz
0
1
0
1
0
TBD
mA
ANALOG BYPASS
Line in to line out
0
1
0
TBD
mA
Line in to headphone out
0
1
0
TBD
mA
POWER DOWN
Power down all
1
X
0
TBD
mA
Power down, VCM enabled
1
0
X
0
0.8
A
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