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PCM5242: Future Strategy of DAC Design for TI

shadders
Expert 1065 points
Part Number: PCM5242
Other Parts Discussed in Thread: PCM1795, PCM5252, PCM1792A

Hi,

In examining the performance of the latest DAC IC’s, despite TI offering DAC’s with 32bit capability, the performance of the latest IC’s (PCM5242, PCM5252) is significantly less than the older TI DAC IC’s (PCM1795).

TI seems to be offering higher bit data (32bit) DAC’s but they are targeted at smartphone implementations, and as such the specification has been relaxed. The older 32bit DAC’s exceed the current available DAC’s by a significant margin, and the latest DAC developments seem to be regressing in terms of performance.

Therefore, will TI be continuing to produce the PCM1795, and will TI also in the future be producing DAC’s which meet the same specification at the older TI1795 DAC IC, which will be used for hifi use, such as a new design or an enhanced PCM1795 (multiple filters, higher sample rate) ?

Thanks and regards,

Richard.

  • 0
    TI__Guru 53973 points
    Hi Richard,

    The PCM1795 is an excellent device! You comments are something I have heard before, and there is not really a complete answer to address your concerns. I think of it like this: What are the key goals of the design? If you are looking for best SNR and THD at any cost in complexity, then the PCM179x devices are the clear choice. But this ultra-high SNR and THD is very difficult to realize in application, as these devices require a complex output amplifier scheme, bipolar supplies, low noise amplifiers, out-of-band noise filtering, and excellent passive component selection. Audiophiles love these parts because of the complexity of this circuit, there are a lot of 'knobs' you can turn in the design to achieve that sound that you want.

    While the PCM5xxx line of devices do not achieve this same level of pure analog output, they bring a lot of other features to the table. They have much better jitter tolerance, much lower out-of-band noise (to the extent that only a simple RC is needed), line-out drive capability, an integrated PLL, integrated charge-pump, advanced digital filters, and a flexible DSP. These are features that our commercial customers love because they simplify the design and BOM.

    The PCM5xxx and the PCM1792a actually have the same output architecture, but the PCM5xxx has a higher analog noise due to the integrated trans-impedance amplifier.

    As for the future of TI's audio DACs - I cannot really comment on that. I can say that we are investing in supporting these devices and that they are still making money!

    Thanks,
    Paul
  • 0 in reply to Paul_Frost
    Expert 1065 points
    Hi Paul,
    Thanks for the reply.

    The performance of the PCM1795 (and PCM1792A) is excellent. For any DAC implementation in Hifi, the bipolar power supplies is in general, not an issue.

    For the PCM5XXX series - they do offer the extras that can be of a benefit - miniDSP, and more filters to select. I understand that BOM is a requirement for smartphones, and low cost devices or non-Hifi devices, but for A/V receivers which usually are DSP based, then a PLL is not really required, and perhaps bipolar power supplies are not an issue either. If the charge pump power supply and trans-impedance output stage diminish the capability and performance as it does for the PCM5XXX devices, then for myself, the use of the device is less appealing. It is a 32bit device - yet has in some instances, a worse performance than 24bit devices. I understand it is a numbers game.

    I am not sure one-size fits all approach is the best strategy in the long term.

    It would be good to see the PCM1795 enhanced with extra filters, and an increased sample rate capability.

    Regards,
    Richard.