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Multiple MAX9814s keep failing after working for some time, draw 4 times more currents and doesn't output anything

Category: Hardware
Product Number: MAX9814

Hi everyone, 

We have been burning MAX9814 AGCs for the last couple of weeks. I have two eval boards of this IC and they work fine, no problems. We did our own PCB and we've been struggling with this IC.

Schematic is representative of what is actually on the board, we took a blank board where just the IC and its supporting circuitry were attached.


Assembly process:

The IC was put on a board by hands and great care was taken to not exceed max temperature of reflow, we've used leaded solder and once it reached melting temp, we did not expose it for more than 5-10 seconds. Ground pad was soldered as well. This is what it looks like when assembled. Pins 9 and 10 needed to be connected because there was a mistake in the schematic (corrected above).  

The setup:

When first powered on, the IC draws ~4.19 mA of current, supplied by benchtop power supply. A signal generator is set for 100 mVpp 1000 Hz sine wave with no offset. Oscilloscope is attached at the other end of cap connected to pin 6, AC coupled with 1 MEG probe.  

Failure mode:

Sometimes, the circuit works exactly as expected for several hours, then goes into failure mode, other times, it starts to fail on the first power on. When circuit works, it amplifies When failing, the current draw increases to 5 mA, then 8 mA, then drops back to 4 mA, oscillating (albeit without known period) between 4 mA to 10 mA until it stabilizes around ~15 mA. The moment the current starts exceeding 4 mA, the gain starts to compress and, until at some point it goes to 0, the output of the IC is floating. 

Questions for Analog:

1. Is it possible to get in touch with someone who can help me troubleshoot this IC?

2. The ICs that we've ordered have "BEM" label on them, while ones attached to eval board have "NDO" on them. What's the difference?

3. Could you please provide us with Gerber/Altium files for the IC eval board? We know that your eval boards work, we want to find out how is our layout different

  • Hello GRPEE34,

    I am not the expert with this part but I did take a look and the pin labeled A/R is supposed to be grounded not tied to VDD.

    However, that said I see that the datasheet does show it tied to VDD for a different attack to release ratio.

    You might want to take an ohm meter to each pin and see if something does not measure correctly from the pin to ground and VDD. It may help to point you in the right direction of what could be happening. 

    You are going to a scope so I doubt you are loading down the output too much. 

    Dave T

  • Hello GRPEE34,

    A few questions:

    • Is the EP floating as shown in the schematic?  It should have a solid connection to ground.
    • Are you certain that none of the pins are having ABS max voltage levels violated?

    The top mark provides production information and can change from time to time.  The EVK top mark is likely just an older assembly material.  I've enquired as to the current top mark and I'll respond back when I have that verified.

    Here is the EVK datahseet where you'll find the layout layers.MAX9814 EV Kit (

    When there is a field failure, normal procedure is to request a FA report.  This will tell us what pins failed and will guide us to fault isolation.  If you're interested in supplying 3 failed units and filling out an FA request, I'll figure out the rest of the procedure for that.

    Mike N

  • Exposed pad is grounded. We are testing it on the bench with VCC set to 5V, so not possible to exceed that. Let us arrange FA report, I'll ship 3 units that have shown the failure mode that I've described with changing DC current. Send me an email please. 

  • I've confirmed ADB is the current Top Mark for the MAX9814.

    I should have a contact in FA group to guide you through FA process shortly.

  • Also, where in the US are you located.  I should be able to isolate the proper FA contact once I know that.

  • I sent you an email with an engineer in our FA department copied.  They should guide you though the RMA process and requesting FA.

  • I've gotten in touch with Analog's quality rep but it doesn't seem to be going anywhere, we don't have an unlimited time on this project. Can I get in touch with someone from Analog to look over our circuit?

  • Alright, I nudged the FA request a bit and it looks like that is moving again.  I'll review your schematic more closely and see if anything jumps out as problematic.

  • Hello, GRPEE34,

    I've got this set up on my bench now (using and EVKit) and I will let it run overnight to see if I am able to see the failure mode.  I have modified my EVKit to match your schematic, and my device is currently drawing 4.2mA on DVDD.

    The part that I am using has a top mark of "NDY", so this is from a different batch than your EVKit and ordered parts.

    Your layout in the microscope pictures looks good for the most part, with slight differences compared to the EVKit.  I don't have access to the Gerber/Altium files for the EVKit, but there are pictures of the EVKit layout on page 5 here: MAX9814 EV Kit (  The circuit is very simple and only on the top layer, so this should let you compare layouts easily.

    The only major difference that I see layout-wise is how the N.C. pins are connected.  On the EVKit layout, these pins are connected directly to the EP instead of going through vias like your design.

    I have a slight worry about the resistor values that you selected for R11 & R12.  These are significantly lower values than what are used in the EVKit.  The total resistance for those in the EVKit is 250kΩ, but on your design, it is only 4.42kΩ.  I am not sure how this will affect the device, but I would recommend changing those to something like 120kΩ each for a total of 240kΩ on that divider network.

    My biggest concern is that these are hand-soldered devices.  How was this soldering done? By hot air, IR reflow, or with a handheld soldering iron?  With hand mounting, I am always concerned that the EP has not been sufficiently heated to ensure a good solder joint.  5-10 seconds at temperature may not be enough time for the solder to flow, depending on how well your ground dissipates heat.

    I will update my results tomorrow when I return to the office.