• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 32 subscribers
  • Views 1195 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM1804: PCM1804 VCOM and VREF decoupling capacitors

Duncan Verheijde
Prodigy 20 points

Part Number: PCM1804
Other Parts Discussed in Thread: TLV320ADC3140, TLV320ADC5140, TLV320ADC6140

The PCM1804's datasheet prescribes some decoupling capacitors for VCOM and VREF. Especially the choice of using 0.1uF tantalum capacitors for VCOM is not that clear to me from a practical point of view. What makes the choice of capacitor type critical on these pins? Would it be a bad idea to replace this by standard 100nF X7R ceramic types? It seems it was done so on the DEM-DAI1804 evaluation board.

We would like to avoid the use of tantalum capacitors and replace them by MLCC's or polymer aluminum types for higher capacitance values where possible..

  • 0
    TI__Mastermind 22950 points

    Hi Duncan,

    A good performance ceramic cap should be fine.

    This is a relatively old part/data sheet and good ceramic caps at low cost were hard to come by. 

    Regards,

    Aaron

  • 0 in reply to Aaron Estrada
    Prodigy 20 points

    Hello Aaron,

    Thank you for sharing your input. It could be very well possible this was decided given a certain component availability consideration. On the other hand, good 100nF ceramic caps shouldn't have been a serious problem those days?

    I was also wondering how the capacitor's ESR could affect the noise performance on this reference node. Such a small 100nF tantalum capacitor has a significant higher ESR compared to its MLCC equivalent. Sometimes buffered voltage reference outputs don't like too low ESR values for decoupling as they may cause instability and/or can increase the higher band noise levels. I hope somebody can comment on this for this particular converter?

    Regards,

    Duncan.

  • 0 in reply to Duncan Verheijde
    TI__Mastermind 30240 points

    Duncan, 

    As Aaron mentioned these devices are pretty old and designed by Burr-Brown around the time TI acquired BB.  because of this our design support on this device is limited,  What I can say is that an X7R capacitor would be fine.  We created some newer test boards to help support these devices and they use X7Rs for just about everything and they work great,  

    one thing I would like to mention, is that we've recently released brand new Audio ADCs  the TLV320ADC3140,TLV320ADC5140 and TLV320ADC6140. 

    There will be a hardware controlled version of these devices coming out as well.  These devices are a bit more modern, require fewer supplies, are lower power, and the performance is similar. 

    best regards,

    -Steve Wilson