TAS54x4C Software Design Guidelines
2
TAS54x4C Software Design Guidelines
The programming of the control system for the device can be broken down into separate functions to
make the programming easier. Use this design guide along with the data sheet.
2.1
Definitions
To following definitions will help the user understand the flowcharts and operation of the device. The H-
bridge output stage has five operating modes:
Hi-Z mode —
The output stage is not switching. All four FETs in the output stage are off and the output
appears as a high impedance or hi-Z state.
Mute mode —
The output stage is switching at 50% duty cycle. The modulated signal is not connected to
the output stage.
Play mode —
The output stage is switching with the modulated signal connected to the output stage.
Low-low mode —
The inductive nature of an audio speaker is capable of some current storage (back
EMF). At turn off the stored current must be controlled before the output stage proceeds to the hi-Z
mode. The low-low mode pulls the output stage to ground to drain the stored current.
Load diagnostics mode —
The output stage in this mode is controlled internally through special states to
measure the condition of the external amplifier load.
Gain and common mode ramps —
In addition to the five operating modes for each H-Bridge output
stage there are also ramps to reduce pops and clicks. During the ramps the status registers report
that the device is not in any of the five operating modes previously listed.
│
MUTE pin —
The MUTE pin has a capacitor that controls the timings required to reduce the potential
pop and click at amplifier turn on and turn off. This pin can also be used for an emergency mute if it
is pulled to ground. By pulling this to ground and then proceeding with I
2
C commands to transition
to hi-Z mode the device is unable to transition between states because the ramps are prevented
until the emergency mute is released.
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TAS54x4C Design Guide
SLOA196 – June 2014
Copyright © 2014, Texas Instruments Incorporated
