I am currently testing an ADUM5401ARWZ-RL and I have come across an issue while attempting to measure the parameter II (Input Currents Per Channel) per the datasheet. For the 5V primary/5V secondary electrical characteristics the parameter II is specified with a -20uA to +20uA minimum to maximum limits for conditions of 0V ≤ Vix ≤ VDDx with a typical measurement of +0.01uA. I have interpreted the conditions to mean that for a specific input VIA through VID, the VDDx refers to the supply voltage that governs the particular input. For example, on the ADUM5401, VIA, VIB, and VIC are all on the left side of the lead frame and thus should be referenced to the VDD1 supply voltage while VID is on the right side of the lead frame so it should reference the VISO supply voltage.
So for my measurements I am measuring the input current for VIA, VIB, and VIC at 0V and at VDDI and the input current for VID at 0V and VISO. For my test case I have set VDD1 to be 5.5V and VSEL is set to 5V so that VISO will be at ≈ 5V. Before I perform the measurement I measure the unloaded VISO voltage and use that as my conditions for the VID input current measurement for the VISO value.
What I am observing is that for the VIA, VIB, and VIC pins, I measure very small input currents (<10nA) for the condition where VIA, VIB, and VIC are 0V but the input current measurement where VIA, VIB, and VIC are at 5.5V, the values I measure across a lot of ~400 parts is ~1uA to ~22uA where some parts (~10) are exceeding the +20uA maximum limit. For the VID pins, regardless of if I am testing at 0V or at VISO I measure very small input currents (<10nA).
When I measure the input current as a function of the input voltage what I observe is that an exponential increase in the input current as the input voltage approaches ~4.9V. Below ~4.9V the input current is very small (<10nA) but the current exponentially increases as the input voltage increases to 5.5V. At 5.5V the input current is now in the 1 to 20s of uAs.
I am also testing a number of different parameters in the datasheet for these devices (VIL, VIH, VOH, VOL, IDD1(Q), VISO, VISO(LOAD), tPLH, tPHL, PWD, tPSKCD, tPSKOD) and all devices pass the testing for all of these parameters with no issues or anomalies. Functionally, all devices appear to be working properly and as expected per the datasheet.
Additionally, I have performed similar testing on a lot of ADUM5402ARWZ which are in the same family of components. This input current behavior was also observed for this part number on VIA and VIB but no longer on VIC as VIC for the ADUM5402ARWZ is on the right side of the lead frame and is referenced to VISO. Based on this additional set of data I do not believe the issue at hand is related to the specific set of components (either ADUM5401ARWZ-RL or ADUM5402ARWZ) but is instead based upon either an incorrect assumption on my part regarding the test conditions for this component (such as the range of VIN to be used for the input current measurement) or this behavior is a phenomenon in the part that is not described in the datasheet. I did review all datasheets from the initial Rev 0 to the current Rev E and the only difference I can note regarding the input current measurement is that in Rev B and all newer revisions the conditions for the input current measurement were not explicitly listed as V ≤ Vix ≤ VDDx whereas in the prior Rev A and Rev 0 it was not listed.
I have checked my testing fixture when no device is present and all currents measured by my system are extremely small (<1nA) so there is no evidence that I can see that it is related to the test fixture itself.
If anyone has any insight into why I might be observing this behavior I would greatly appreciate any information.
Thank you