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ISOUSB211: Help to review shematic

Part Number: ISOUSB211


Hi experts,

My customer is using ISOUSB211, could you help to review schematic? Many thanks.



  • Hi Victoria,

    Thank you for sharing the schematic for review.

    The schematic mostly looks good, I had just a few inputs which I am listing below.

    1. I see that customer has used internal LDO of ISOUSB211 to generate 1.8V. This dissipates power inside device causing device to heat-up slightly.
      1. This is not a problem if customer application doesn't require high temperature operation but if they need operation beyond 70C, then I recommend them to use external LDOs. This is described in sections 8.3.1 and 10.3 of ISOUSB211 datasheet.
      2. It is important to make sure all the decoupling caps are positioned close to device pins for reliable operation of device, please refer to the layout example in datasheet.
    2. The EQxx pins should be made HIGH or LOW based on your PCB trace lengths on respective sides to compensate for the losses. If you are not using this feature then we recommend that you make these pins LOW. The connections shown in datasheet are example connections only.
      1. You can refer to the below App Note for more details on the usage of EQ pins.
        1. Compensate for Channel Loss with Equalizer Settings on High-Speed USB Isolators
    3. The 22Ω resistors in series with DD± and UD± pins are not needed for ISOUSB211 operation, we recommend that they removed or replaced with 0Ω resistors for the optimum performance of ISOUSB211.
    4. The USB standard recommends that VBUS pin on the peripheral connector has at least 100µF capacitor to maintain a stable power supply. Please consider using this to be compliant with the USB standard. Thanks.

    Koteshwar Rao