Tripath Technology, Inc. – Preliminary Technical Information
AM MODE
The TCD6001 is typically configured as a high power, high efficiency, four channel switching amplifier. The
TCD6001 also has an additional amplifier mode named “AM Mode.” When used with a Tripath Technology
power stage also equipped with AM Mode, the TCD6001 can be configured as a Class B amplifier as
opposed to the normal Class T amplifier by pulling the AM_IN pin to a logic high level.
AM mode significantly reduces EMI generation since the output amplifiers are now operated in linear mode.
Operating in Class B mode also reduces the power stage’s efficiency especially at low to medium output
powers. Due to this increased power dissipation, it is recommended that the AM mode is used for
applications such as AM radio playback where the average output level is minimal and a switching amplifier
would most effect radio reception.
PREDICTIVE GAIN CONTROL
The Predictive Gain Control (PGC) automatically sets one of four different pre-gain levels depending on the
Channel Volume level (registers 25h – 2Ah). The PGC allows less gain to be used for lower volume levels.
This results in greater digital resolution and lower noise floor. When PGC is enabled (register 3Dh bit D7 is
set to ‘1’), PGC settings are changed automatically by the Channel Volume. When PGC is disabled, the
system’s pre-gain level is always set to full gain.
Channel Volume Range
FFh – F4h
PGC Setting
Full Gain
1/2 Gain
F3h – E8h
E7h – DCh
1/4 Gain
DBh – 00h
1/8 Gain
POST-GAIN
The TCD6001 has four “post-gain” settings: -6.5dB, -3.5dB, 0dB, and +2.5dB. A post-gain setting of 0dB is
considered nominal and allows the power stage to achieve rail to rail clipping of approximately 10% THD.
Post-gain settings of –6.5dB and –3.5 dB have lower noise floor but the TCD6001 may clip internally before
the power stage reaches its own clipping points – reducing maximum output power. A post-gain setting of
+2.5dB allows for extreme clipping at the power stage outputs at the cost of a higher noise floor.
The user may use low post-gain at low volume levels to take advantage of the lower noise floor and use high
post-gain at higher volume levels to take advantage of the full range of the power stage. Precautions must
be taken while changing post-gain to prevent DC offset. The automatic DC offset cancellation settings will
have been affected by changes in post-gain. To avoid this problem, the software that is controlling the
TCD6001 through the I2C port should store DC calibration values for each post-gain setting and swap
between them as in the following procedure:
1. Set post-gain to low and channel volumes to 00h.
2. Un-mute.
3. Wait for calibration to complete.
4. Read values in the “Calibration Readback” registers and write them to the “Calibration Bank”
registers.
5. Mute.
6. Set post-gain to high and channel volumes to 00h.
7. Un-mute.
Now the calibration bank contains the DC calibration values for low post-gain and the TCD6001 has stored
the DC calibration values for high post-gain in its internal registers. When the CFn bits (register 2Fh bits
D5..D0) are set to ‘1’, the values stored in the Calibration Bank are used. When the CFn bits are cleared to
‘0’, the internal registers that hold the automatic DC calibration values for high post-gain are used. If the
PGC is enabled, the software should only switch between low and high post-gain modes when the PGC is in
1/8 Gain mode. This is because the values stored in the Calibration Bank will only be valid for the PGC
mode that was in effect when the channel volumes were set to 00h and automatic DC calibration took place.
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TCD6001 – JL/Rev. 0.9/07.05
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
