What exactly was changed from the original version of ADuM5402W to the ADuM5402W-1?

Question What exactly was changed from the original version of ADuM5402W to the ADuM5402W-1? Answer The ADuM5401W-1/ADuM5402W-1/ADuM5403W-1 versions of the isolators provide an upgraded voltage reference to ensure proper startup under all load conditions. Please refer to page 23 of the latest REV E of the ADuM5402 datasheet. This page provides a detailed description of the startup issues which were found on the ADuM540x devices and it also documents the restrictions which apply to the use of ADuM540x to avoid or provide a workaround for the startup problem. Because of the upgraded voltage reference, these restrictions do not apply to the ADuM5401W-1/ADuM5402W-1/ADuM5403W-1 devices and this is why we recommend the -1 devices for new designs. Nothing else on the datasheet has changed.

ADuM5402 input behavior

Question We use the ADUM5402 on many of boards to generate the isolated 3V3 for our POE controller. As part of that circuit a 3V3 voltage is generated through a FET into Pin 12 of ADUM5402 to indicate when POE power is applied. The voltage comes out Pin 5 to power an led through a 100R resistor. It works fine, but i am seeing issues in production, that the LED comes on when no POE is applied. I think maybe some leakage current is going through the FET and voltage going into Pin 12 of ADUM5402 is floating (or at least floating between a logic 1 and logic 0) I have looked at the datasheets and other documentation on the your website to try and find out what to do with an input pin that is not connected or even floating. i.e. would a 100K pull down on Pin 12 be ok? Answer The inputs are very high impedance, they will float to midrange and give unpredictable behavior. A pull down would probably be a good solution, 100kohm seems reasonable.

Question I would like to know if it is OK to change the Viso pin 16 while the chip is powered (changing from 3.3 V to 5 V secondary voltage, controlled from the primary side using one of the internal channels). It would help powering / un-powering a uC with limited pin count using its BOD. Answer The ADuM5402 when power is OK to change Vsel to make the Viso go from 3.3V to 5V. You do need to have 5V VDD1 to do this, since 3.3V VDD1 to 5V Viso is not supported.

ADuM5402: EMI layout recommendation

Question Could you please kindly recommend the type of ceramic disc safety capacitor to mitigate EMI? There are various type of ceramic disc safety capacitor, for e.g., X1, X2, Y1, Y2. I would appreciate if you could recommend a general one which can be used in this case. Answer For recommendations on ADuM5402 EMI mitigation layout, please refer to the attached layout. We have been using 100pF ceramic safety caps from Murata. These caps have a resonance near 300MHz. We are working with Murata part DE1B3KX101KA5B components right now, it should be a good starting place..

ADUM5402: 5V supply disturbed by device's DC/DC converter.

Question

5V supply is disturbed due to the ADUM5402 isolator's DC/DC converter. Are
there any recommendations on layout that might help?

Answer

We have an application note AN-0971 titled recommendations for control of
radiated emissions with isoPower Devices. iCoupler digital isolators with
integrated isolated power (isoPower) employ isolated dc-to-dc converters that
switch currents of ~700 mA at frequencies as high as 300 MHz. Operation at
these high frequencies raise concerns about radiated emissions and conducted
noise. PCB layout and construction is a very important tool for controlling
radiated emissions and noise from applications containing isoPower components.
This application note identifies the radiation mechanisms and offers specific
guidance on addressing them.

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ADUM5402: 5V supply disturbed by device's DC/DC converter.