ADUM3160 Problems

I am having difficulties getting USB coms using the ADUM3160. The downstream side is connected as shown in figure 5 page 3 of the application note to my USB transceiver which is a FTDI USB to Serial UART (MM232R). VBUS2 is supplied with 5v via regulator on the device, I have the suggested caps fitted and can see the expected voltages on VCC and VBUS pins on both sides of the device. The upstream side of the device is connected to my laptop via the USB cable. I have not used any series resistors on D+ or D- lines as mentioned in a previous thread as this is not mentioned in the datasheet. I cannot see high level on D- or low on D+ when the device is idle, on both sides D- and D+ is  0v. I have attached photos of my schematic a circuit board.

  • 0
    •  Analog Employees 
    on Dec 3, 2014 4:42 AM

    Hello Joseph,

    Please clarify what you mean by "VBUS2 is supplied with 5v via regulator on the device"

    Do you have VBUS2 connected to a 5V power supply and Vdd2 is generated by the internal regulator?

    Start by checking the power connections.  The part does not supply isolated power across the barrier, so a supply is required for each side.  An additional dc/dc converter is required for that.

    Please verify that the pull-up is being applied by the peripheral controller.

    Can you remove the isolator and connect the peripheral to the laptop and get it to work?

    Let me know what you find out.


  • Hi MS Cantrell,

                             Thanks for getting back to me.

    My peripheral device  has its own 3.3v and 5v power supply that powers the MCU and the MM232R. I have used this power supply to supply 5v to the VBUS2 pin on the downstream side of the isolator. 3.3v for VDD2 is derived from the internal regulator.

    VBUS1 is supplied with 5V via the USB cable from the host device which is a laptop. And again 3.3v via the internal regulator for VDD1.

    Do you mean the pullup on D+ line? Please see below extract from MM232R datasheet, seems to confirm a pullup on D+ when the Host is powered up?

    Yes without the isolator in place I have USB comms with the device.

    Reading the datasheet again I've noticed that for full speed operation there must be a series 24R resistor on D+, D- on both sides of the device.

  • Got it working now. Added 24R series resistor to D+,D- lines both up and downstream. Applied 5v onto the MM232R 5v USB pin in order to emulate the Host powering up.