ADN8835 Breakdown

Hi Ucatak ,

Thanks for reaching out. 

I have reviewed your schematic and it looks fine for me. values of components setting the VLIM and ILIM are correct. It is a normal response that LDR is pulled to GND with IN2P (and also OUT2, since it acts as a buffer) to be pulled to GND. You can refer to the figure 37 of the datasheet (OUT2 vs. LDR voltage). 

• What is the VIN you are using?
• You said that the part brokedown, what is the indication of breakdown?
• Have you tried lowering the IN2P voltage again and see the LDR and SFB response?
• What load are you using? is it a resistor?
• Have you tried it first with no load connected and observe the LDR and SFB output if it will follow the datasheet curve? that is the basic troubleshooting that i am doing to check whether the part is still good.

Are you using the evaluation board or you have your own designed board?

Thanks,

-Noel

Dear Noel,

Thank you very much for the prompt reply. 

We are using both evaluation board and our own board. All the ICs which was brokedown on our board. We did not use evaluation board in full range. 

Yes, we have already reviewed the figure 37 on the datasheet. We were aware of this response before design stage.
Here is the answers to your questions.

• What is the VIN you are using? -- Our VIN is 5.5V
• You said that the part broke down, what is the indication of breakdown? -- Even the pin 13 (EN/SY) low, ADN8835 is overheating. ADN8835 is not functioning and over heating.  When we remove IC from the board, between LDR - PGNDL pins are short, resistance between them is zero We think that ADN8835 is  continuously "LDR Short-Circuit Threshold ILDR_SH_GNDL LDR short to PGNDL, enter hiccup"
  
  
• Have you tried lowering the IN2P voltage again and see the LDR and SFB response? -- It continuously entering Hiccup so we couldn't try it.
• What load are you using? is it a resistor? -- We have used both peltier and resistor. It supplied 1.9A to 2.4 ohm resistor when IN2P pin supply with DAC 2.3V. When Peltier used as the load, with IN2P input 2.5V with our DAC,  1A-1.2A current flows over peltier. The IC works without problem for sometime like 1-3 days, if it is not used in full range performance or changing IN2P in small steps. Our observation is when IN2P input (from our DAC) changed in big steps (1.25V to 2.2V or 1.25 to 0.3V) leading instant current change from 0A to 1A and the problem is occurring and IC breaks down, somehow.
• Have you tried it first with no load connect. -- After breakdown with or withour load there is no difference IC is overheating. 

In summary we observed all breakdowns at instant input changes on IN2P (1.25 to 2.15V-2.5V or 1.25 to 0.35-0V)

Thanks,

Best Regards, 

Ugur