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ISOUSB211: DPEVM optimal configuration, feedback, clock source

Anwar Ali Vali Mohamed
Prodigy 90 points
Part Number: ISOUSB211

Hi,

I am evaluating ISOUSB211DPEVM for USB Audio use where the ISOUSB211DPEVM is inserted in between the path of music streamer USB output (type A) and USB DAC input (type B).  Another competing product is ADUM4166.  Subjective comparison was made against FCPGA-based Intona 7055-C USB Isolator.

Why is the default PCB configuration not to use the external 3.3V linear voltage regulator but instead use internal LDO to generate 3.3V from VBUS?  Is this the more optimal configuration?  Why waste the external voltage regulator?  And the need to desolder / add connections to change its configuration.  Using jumpers should be better.  Having terminal blocks for connecting external DC power to the PCB makes more sense.

The competing product ADUM4166 uses external 24MHz crystal/clock for retiming.  What is the clock source for ISOUSB211?

Thanks,

Anwar

  • +1
    TI__Expert 3482 points

    Hi Anwar,

    Thank you for reaching out to us!

    The left side of the EVM uses the internal LDO and the right side uses the external LDO.

    The EVM demonstrated two different power options for VBUS and V3P3V. In addition,

    it also provides the flexibility to users to change the configuration by populating and removing 0 ohm resistors.

    Please look at section 9.3 Thermal consideration in the datasheet for the pros and cons for different power options.

    One of the reasons that we decided not to go with jumpers is for radiated immunity consideration. These jumpers will pick up more noise and

    degrade the power and signal integrity.

    ISOUSB211 has a built-in clock. Hence, there is no need to use an external clock.

    Regards,

    Alfred

  • 0 in reply to Alfred Chong
    Prodigy 90 points

    Hi Alfred,

    Thank you for responding quickly and noted your explanations.  I already modified the board (use left side 3V3 external regulator, use external 2-rail 5V LPSU for both left and right sides, 5V from USB A disconnected by removing L1 and C32).  Removing / soldering SMD parts by hand is not easy - PCB can get damaged if not careful.

    Modified EVM

    My initial impression for audio use from listening tests - it cannot match the resolution of Intona 7055-C but the ISOUSB211 indeed sounds more musical.  That's why I asked about the clock for addressing the lack of resolution issue.  Now waiting for ADUM4166 to arrive...

    Regards,

    Anwar