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ISOUSB211: [CITECH] Schematic Review Request

MJ Jeon
Genius 5240 points
Part Number: ISOUSB211

Hi, TI support team

A request for review of the attached circuit has been received from the customer.

This is the schematic using ISOUSB211.

Please review.

Thanks.

Regards,

MJ

  • 0
    TI__Mastermind 24885 points

    Hello MJ,

    Responses during the holiday season will be delayed, we will review and provided feedback when we return to the office.

    Best,
    Michael

  • +1
    TI__Guru 54445 points

    Hi MJ,

    Thanks for sharing the schematic for review. Please see below my review feedback,

    1. Side 1 (host side):
      1. I see that the schematic is missing decoupling capacitors on most of the power supply pins. Decoupling capacitors are necessary for the device to operate normal without which the device will not be able to meet datasheet specifications and might not even function.
        1. Please see section 9 in datasheet for recommended decoupling capacitor values for all the power supply pins.
        2. Please also refer to figure 10-1 for example schematic with decoupling capacitors.
      2. Based on the resistors that are populated and unpopulated (NC), I could make out the following.
        1. VBUS1 is supplied with 5V.
        2. V3P3V1 voltage of 3.3V is generated using internal LDO.
        3. VCC1 and V1P8V1 pins are applied with external 1.8V.
        4. Assuming the above connections, this looks good.
      3. Regarding EQxx pins, you might want to give provision for pull-up and pull-down resistors so that these can be experimented for the optimum performance during testing, atleast in the prototype schematic.
      4. Assuming that the host is also going to support peripheral charging, the CDP advertising needs to be done only on downstream facing peripheral side, i.e., Side 2 in this case. Hence, CDPENZ1 should be made HIGH while CDPENZ2 should stay LOW to support CDP advertising on Side 2 only.
    2. Side 2 (peripheral side):
      1. I see that the schematic is missing decoupling capacitors on most of the power supply pins. Decoupling capacitors are necessary for the device to operate normal without which the device will not be able to meet datasheet specifications and might not even function.
        1. Please see section 9 in datasheet for recommended decoupling capacitor values for all the power supply pins.
        2. Please also refer to figure 10-1 for example schematic with decoupling capacitors.
      2. Based on the resistors that are populated and unpopulated (NC), I could make out the following.
        1. VBUS2 is supplied with 5V.
        2. V3P3V2 is supplied with 3.3V
          1. Please note that when VBUS2 is supplied with 5V, V3P3V2 is generated using internal LDOs. Hence, there is no need to connect external 3.3V to V3P3V2.
          2. If you do not want to use internal LDO, then connect external 3.3V supply to both VBUS2 and V3P3V2.
        3. VCC2 and V1P8V2 pins are applied with external 1.8V.
      3. Regarding EQxx pins, you might want to give provision for pull-up and pull-down resistors so that these can be experimented for the optimum performance during testing, atleast in the prototype schematic.
      4. Assuming that the host is also going to support peripheral charging, the CDP advertising needs to be done only on downstream facing peripheral side, i.e., Side 2 in this case. Hence, CDPENZ2 connection looks good in the schematic.
      5. I see that the schematic uses 10µF + 100nF on the 5V pin of USB connector. Please note that the USB standard requires that this 5V to have 120µF capacitor to support the inrush current requirement by the peripheral device. Please refer to section 10.1.1 and figure 10-1 of datasheet for more details.

    Let me know if you have any questions, thanks.


    Regards,
    Koteshwar Rao