Problem with ouput voltage VISO of ADUM6403

Sebastien:

It sounds like you may have a VISO startup issue with the ADuM6403, if it is in one configuration giving you 5.0V output and in another giving 3.7V.  Can you capture a scope waveform of the VDD1 and VISO?

If it is a VISO startup issue, there was a problem with this about 4-5 years ago that was fixed with a die revision.  Can you tell me the data code on the ADuM6403 with the issue?

Regards, Brian

Thanks you for your help.

Our configuration must give 3.3V output. Here the VISO and VDD1 signals. VDD1 is connected to VDDL.

The data code is 1519.

Did we miss something?

Regards, Sebastien

Sebastien:

The date code 1519 looks ok. Here are some questions:

1. Can you give me the complete part number?

2. If you try without the 160 ohm between VISO and GNDISO does it give you the correct 3.3V output?

3. If you try another IC of the ADuM6403, does it also have the same issue with not getting 3.3V output?

4. Can you take scope waveforms that show the startup from of VDD1 and VISO on the same waveform?

5. Also, can you show the ADuM6403 schematic and the layout including the bypass capacitors?

Regards, Brian

Hi,

1. The complete part nuber is: ADUM6403 ARIZ #1519* 3139532.1.

2. From the last test, I removed the 160 ohm betwwen VISO and GNDISO. I only left the 100nF and 10uF capacitors between VISO and GNDISO. The output VISO still 3.7V.

3. We have also ADUM6403s that give 3,87V, 4,29V, 4,46V and 5,04V on the output VISO pin.

4. With only 100nF and 10uF capacitors between VISO and GNDISO pins, here VDD1 and VISO signals at power-up:

We got an overshoot up to 4.3V.

5. Here the schematic used and the layout:

and the layout

All capacitors are on the bottom

Regards,

Sebastien

Brian:

Do you have the same problem on some ADUM6403s?

Do we use correctly the ADUM60403?

Regards,

Sebastien

Sebastien:

I don't think this is normal behavior for the use of the ADuM6403.  I have an idea that you may have a voltage on the inputs VIA, VIB or VIC from your VCO signals that is above the setpoint of VISO = 3.3V and is raising the VISO voltage from the input signal through an internal ESD diode to the VISO pin.  Measure the voltages on the VIA, VIB or VIC with a scope to see if any of these signals raise above the normal 3.3V level.

Regards, Brian

Brian:

We check the voltages on the VIA, VIB, VID and VISO signals on another ADuM6403 which has the same behaviour. The volatges are the following:

VIA = VIB = VID = 0V

VISO = 4.1V

Here the screen shoot:

We also checked at power-up:

None of the input signals are above 3.3V.

We tried too with VIA, VIB, VIC, VID, VOA, VOB, VOC and VOD  left floating. The voltage on the VISO pin still 4.1V.

Best Regards,

Sebastien

Sebastien:

I don't see anything wrong with your setup but it looks like there is an issue with the ADum6403 parts you are using.  Can you send me 1 or 2 parts that are having this problem of output voltage not being at the 3.3V setpoint?  We can test them here. I can send you an email if so.

Regards, Brian

Brian:

We can send you 2 parts.

Regards,

Sebastien

Sebastien:

I can look on the bench at the 2 units. To have a Failure Analysis done, I would ask you to have 2 parts with this problem sent back through your distributor that you purchased the parts from.

Regards, Brian