Datasheet

TAS5508C
SLES257–SEPTEMBER 2010 www.ti.com
The crystal time base allows the TAS5508C to determine the CLK rates. Once these rates are
determined, the TAS5508C unmutes the audio.
3.2.3 Back-End Error (BKND_ERR)
Back-end error is used to provide error management for back-end error conditions. Back-end error is a
level-sensitive signal. Back-end error can be initiated by bringing the BKND_ERR terminal low for a
minimum 5 MCLK cycles. When BKND_ERR is brought low, the PWM sets either six or eight channels
into the PWM back-end error state. This state is described in Section 2.12. Once the back-end error
sequence is initiated, a delay of 5 ms is performed before the system starts the output re-initialization
sequence. After the initialization time, the TAS5508C begins normal operation. Back-end error does not
affect other PWM modulator operations.
The number of channels that are affected by the BKND_ERR signal depends on the 6-channel
configuration signal. If the I
2
C setting 6-channel configuration is false, the TAS5508C places all eight
PWM outputs in the PWM back-end error state, while not affecting any other internal settings or
operations. If the I
2
Csetting six configuration is true, the TAS5508C brings the PWM outputs 1–6 to a
back-end error state, while not affecting any other internal settings or operations. Table 3-4 shows the
device output signal states during back-end error.
Table 3-4. Device Outputs During Back-End Error
SIGNAL SIGNAL STATE
Valid Low
PWM P-outputs M-state – low
PWM M-outputs M-state – low
HPPWM P-outputs M-state – low
HPPWM M-outputs M-state – low
SDA Signal input (not driven)
3.2.4 Speaker/Headphone Selector (HP_SEL)
The HP_SEL terminal enables the headphone output or the speaker outputs. The headphone output
receives the processed data output from DAP and PWM channels 1 and 2.
In 6-channel configuration, this feature does not affect the two lineout channels.
When low, the headphone output is enabled. In this mode, the speaker outputs are disabled. When high,
the speaker outputs are enabled and the headphone is disabled.
Changes in the pin logic level result in a state change sequence using soft mute to the hard mute (M)
state for both speaker and headphone followed by a soft unmute.
When HP_SEL is low, the configuration of channels 1 and 2 is defined by the headphone configuration
register. When HP_SEL is high, the channel-1 and -2 configuration registers define the configuration of
channels 1 and 2.
3.2.5 Mute (MUTE)
The mute control provides a noiseless volume ramp to silence. Releasing mute provides a noiseless ramp
to previous volume. The TAS5508C has both master and individual channel mute commands. A terminal
is also provided for the master mute. The active-low master mute I
2
C register and the MUTE terminal are
logically ORed together. If either is set to low, a mute on all channels is performed. The master mute
command operates on all channels regardless of whether the system is in the 6- or 8-channel
configuration.
When MUTE is invoked, the PWM output stops switching and then goes to an idle state.
46 TAS5508C Controls and Status Copyright © 2010, Texas Instruments Incorporated
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