SLASE12A July 2014 – October 2014 PCM5242
PRODUCTION DATA.
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
Differential outputs DAC's are regularly used where higher performance is required from them compared to single ended output DACs. They offer twice as much output voltage for the same power supply, along with noise cancelling effect of differential signaling. The PCM5242 makes an ideal front end for both analog input speaker amplifiers and headphone amplifiers with its higher voltage differential output and low noise floor.
A new trend in portable applications are termed "Hifi Smartphones". In these systems, a standard portable audio codec continues to be used for telephony, while a separate, higher performance DAC and Headphone Amplifier is used for music playback.
Figure 80 shows a complete circuit schematic for such a system. The digital audio is fed into a high performance DAC. The PCM5242 is a 32-bit, stereo DAC.
For optimal performance, the TPA6120A2 is configured for use with differential inputs, stereo use, and a gain of 1V/V.
The TPA6120A2 requires a bipolar power supply to drive a ground centered output. The application employs a TPS65135 DC-DC converter that generates ±5V from a single 3.3V supply.
The PCM5242 DAC is configured for a 1VRMS output so that clipping is avoided should the 3.3V power supply sag. The PCM5242 offers a ground centered output, so that no DC blocking capacitors are required between it and the TPA6120A2. (Page 1, Register 2)
w 98 00 01 # PCM5242 to Page 1
w 98 02 11 # PCM5242 output to 1 Vrms
w 98 00 00 # PCM5242 back to page 0
w 98 3B 66 # set auto mute time to six seconds of audio zero.
w 98 3C 01 # Left Vol register controls both
w 98 3D 4F # Change left channel volume, right will follow.
w 98 3F BB # set vol changes for every 4 samples, 0.5 sample steps.
In this particular application, the TPA6120A2's performance is transparent and the performance of the system is dictated by the PCM5242 DAC, even into a 32-Ω headphone load.