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AMC7820 going bad

Other Parts Discussed in Thread: AMC7820

I am using amc7820 for a laser application.In that there are 24 amc IC's.Certain AMC ic's are going bad at times and when replaced with a new its working perfectly. These 24 amc's have the same circuit.Is there any particular reason for that?

Also in the amc IC am using,its written AMC7820Y 090512T.What does these numbers represent?


And in one of the AMC's ,OPA1 always got output pin with 5V even with both the inputs at 0V?what can be the reason?This OPA1 is used for laser pump drive with negative feedback.The output of the driver section is having zero current the negative feedback also has 0V.(0.007 to be specific at both inverting and non-inverting pins.). But the output pin has got 5V even when the pin is isolated from rest of the circuits.

  • Hello John,

    To help us better understand the issue can you supply a schematic of the circuit?  This will be very helpful in debugging the issue.

    The numbers written on the device "090512T" usually relate to a date code when the device was manufactured, as well as lot number for tracking.

    Best Regards,

    Matt

  • Hai Matt,

    The third issue that i posted was solved.That was a resistor value which was placed was not the correct value.


    but still we face the amc issue thats it going bad.3007.Cooled Pump 1.pdf


    I have attached the schematics of a one pump that we are using.We have 24 similar circuits.the SPI lines are driven through a buffer SN74LVC3G07DCUR.


    And about the device number "090512T".Does it represent DD-MM-YY?


    If its like that,The ic was manufactured in 2012.So will there be any problem if we use it now?

  • Hello Jovin,

    I'm glad that you were able to figure out one of your issues.  To answer your question regarding the device number:

    The device number for this particular device is specified in the following format YMXXXXX, where the first digit represents the last digit of the year, and the second represents the month.  The remaining digits and letter correspond to a manufacture code.  This device was created 09/10.  Most distributors build up a stock of parts, so it is common to receive older devices.

    Can you exactly specify how the AMC7820 device is improperly working.  Is it not able to communicate with your micro-controller?

    Is the date code different than other AMC ICs used on the board?

    Best Regards,

    Matt

  • Hii Matt,

    On Normal working,All the 24 AMC IC's are working properly and the data lines will be reading the adc values properly.But at times these adc lines will be showing 0 reading.None of the adc will be working.All the 24 amc willl be showing 0 .


    One time when I checked,The MOSI line was showing a resistance of 67 ohms with respect to ground.Then by lifting MOSI pin of each amc,i was able to find the faulty AMC.After replacing the amc the issue was solved.


    But this problem keeps repeating.One of the AMC's keeps getting damaged and its random.Not a particular amc..


    So what can be the issue.Have you got any issue like this before?

    Regards

    Jovin

  • Hello Jovin,

    I'm assuming that all 24 AMC7820 devices share the SPI bus, and all have different chip selects (/SS), that are controlled through a PC or digital communication module.

    Regarding the damaged chip:

    1. Have you tried to isolate the device from the other 23 and read voltages at supply inputs?
    2. Have you recorded the state of the SPI inputs, or a waveform during a SPI transaction?
    3. You mentioned that the MOSI line was showing a resistance of 67ohms to GND, where you able to verify this resistance on the damaged device?

    Best Regards,

    Matt

  • Hai Matt,

    All the 24 AMC's share the same SPI bus.And all have different chip selects.


    1.We isolated the pins from the device and read the voltages and all the voltages were steady.

    2.We checked the waveforms using logic analyzer and we were able to see clock and  data being sent on MOSI line.but there was no response on MISO.Also we checked the clock on CRO and it was steady.We were using 1Mhz clock and also we checked for 200Khz also.

    3.Yes.The damaged device was showing 67ohms.After removing the damaged ic from the board also we checked the resistance and it was showing the same 67 ohms.

    Also what is the ESD level of the AMC7820 IC.?Is there any internal ESD protection for the IC?

    Regards

    Jovin

  • Hello Jovin,

    The AMC7820 pins have ESD protection circuitry as the first active element on the chip.  All input and outputs have protection diodes connected to supply and ground that remain reverse biased under normal operation.  

    ESD safe handling should always be practiced when handling devices, as integrated circuits can still be damaged from ESD if mishandled.  ESD damage can range from subtle performance degradation to complete device failure.  Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device no to meet its published specifications.

    I will forward this thread to other colleagues within my group, and will update this post with any feedback I receive.

    Best Regards,

    Matt

  • Hello Matt,

    Thanks for your response.


    Best Regards

    Jovin