IC Damage

Hi AD8205 ,

Apologies for missing this thread. We will be looking into this and get back to you. 

Regards,

Gilbeys

Hi AD8205,

Thank you for reaching out.
I don't see any problems with your supply and input conditions for the AD8205. It should be able to handle the Common-mode voltage of 28V, and the differential voltage the load current and shunt resistor introduced to the AD8205 ~75mV.

Though, you've mentioned that at a load current of 0.55mA you're already getting 0.63V or 630mV?
with a very small load current running through Rshunt, the differential voltage at the input should only be around 13.75uV multiplying it by 50 is not even enough to dominate the output offset which is 50mV according to the datasheet. Can you double check if the load current is actually 0.55A instead of 0.55mA?

Also, a schematic diagram showing the input connection and output connection of the AD8205 + pictures of your setup will be able to help us assess the issue further.
Thank you!

Best Regards,
Dann

Hi Dann,

Thank you for replay.

The load current is actually 0.55A @5V input.  it was a mistake for my end. Please find the circuit attached.

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Hi AD8205,

This is interesting as the Common-mode voltage mentioned is not exceeding the abs-rating of the AD8205.
Have you tried isolating AD8205 (removing the output circuits from it) and applying the 28V common mode voltage? Can you probe the inputs and output using an oscilloscope when you do it? this way we may be able to see where it actually broke down.

I would think that you already fabricated a PCB board for your design. can you also provide us a screenshot of the layout surrounding the AD8205? we may be able to find some faults there too. Last thing, you're using a 0.025ohm Rshunt instead of 0.05ohm right? the schematic shows a 0.05ohm shunt but your functionality test coincides with using 0.025 shunt resistor. Just want to clarify.

Thanks.

Dann

Hi,

Shunt resistor  value is 0.025 ohm. PCB section is attached for reference.

I am unable to probe the input or output, once load is connected the IC will be faulty.  Without load no issue matches input voltage and output is near to zero ( in multimeter equal to 0.025V).

once IC is faulty the default output voltage is 2.4V)

/cfs-file/__key/communityserver-discussions-components-files/1171/8037.New-Bitmap-Image.bmp

Hi AD8205,

Thank you for the patience.
Apologies I missed getting back to you.

I rechecked the schematic and just noticed that your circuit have an inductive load. And usually, a clamp diode must be placed in order to protect the AD8205 on a possible voltage reversal, especially if your common-mode voltage input suddenly went out. Further explanation is written in the datasheet section on page 11.

This is also the reason why I want to probe the input side when you apply your load.
When the common-mode voltage reversed, your -28V (or possibly higher) will exceed the abs max voltage of -25V. 

Hope this helps.

Best Regards,
Dann

Hi Dann,

Thank you for the replay.

I removed inductor and tested only resistive load. I am getting same issue. I will check load inductor with diode and I will update the result. Thank you.

Regards,

Praveen