Cirrus Logic CS4234 - Manual (Page 74)

DS899F1 74
CS4234
10.ORDERING INFORMATION
11.APPENDIX A: INTERNAL TRACKING POWER SUPPLY SIGNAL
The tracking signal for a Class H amplifier tracks the envelope of the maximum of any arbitrary number of input sig-
nals (up to 32 channels for the CS4234). This tracking signal is used to modulate the output voltage of a switch mode
power supply (SMPS), which serves as the rail voltages for an audio amplifier. The main goal in any tracking algo-
rithm is to maximize the efficiency of the Class H amplifier by creating a signal that causes the rails of the SMPS,
sometimes referred to as a tracking power supply or TPS, to track the amplified audio signal as closely as possible.
However, the tracking algorithm must also ensure that the amplifier never clips due to the rail voltage being brought
too low relative to the output voltage swing of the audio amplifier.
In order to track the output voltage swing of the amplifier without causing clipping, three controls are provided to
ensure the tracking signal stays above (higher amplitude) and ahead of (occurs earlier in time) the output voltage
swing of the amplifier. These controls and their respective effects on the tracking signal output on DAC5 are detailed
in
Figure 47 and listed in the following sections.
With the exception of the Gain Matching control, the appropriate levels for the tracking controls are usually deter-
mined experimentally, on an application by application basis. The reason is because the transitioning speed, or
bandwidth, of the SMPS is heavily influenced by the capacitance connected to the output nets of the SMPS, the
topology of the SMPS, the modulation technique, and the bandwidth of the error amplifier in the feedback loop.
Product Description Package Pb-Free Grade Temp Range Container Order#
CS4234
4 In/5 Out CODEC
with Programmable
Group Delay
40-QFN Yes Automotive -40° to +105°C
Rail CS4234-ENZ
Tape and
Reel
CS4234-ENZR