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Critical Temperature of ADC12D1000CIUT/NOPB

Amith Bhat
Intellectual 275 points
Other Parts Discussed in Thread: LMX2581, ADC12D1000

Hi,

I am using ADC12D1000CIUT/NOPB ADC in my Design. We have configured the ADC with both channels powered up and the device is in TPM Mode.(Non ECM Mode).

The clock input to ADC is from LMX2581 clock synthesizer (Configuring for 1 GHz) and we are not getting the clock output from synthesizer. (We are working on register settings of the device)

We are using xilinx FPGA as Master and the device is of commercial grade.

My queries are as below,

1. The ADC12D1000CIUT/NOPB device is getting heated up extremely (71 degree celcsius) with the above settings mentioned.

Is this the normal behavior of the ADC in these settings?

2. The Xilinx FPGA Device is also getting heated up till 67 degree celsius. For Commercial grade device, this temperature is a concern. We tested the temperature of FPGA by power downing I and Q channels (PDI,PDQ= 1) and we found the temperature is normal for bothe ADC and FPGA (Around 47 to 50 degree celsius)

What may be the reason for such a high temperature at FPGA?

Please help me out to debug the cause for such a critical temperature at ADC and FPGA.

  • 0
    TI__Mastermind 43830 points

    Hi Amith

    Regarding your questions:

    1) If the synthesizer is not generating an output, the AC coupled inputs of the ADC12D1000 clock receiver will be biased at the normal operating point, but the + and - inputs will be at approximately the same voltage. In this condition the high gain clock receiver will cause the ADC to be clocked on whatever small noise, etc. is present at the inputs. Though the ADC is not operating at a predictable frequency, the self-clocking rate will be high enough to cause the device to consume a significant amount of power. Tests in a lab setup gave an ADC temperature of 65 degree C and FPGA temperature of 49 degree C. For comparison purposes, with the same ADC operating at 1600 MHz clock rate the ADC temperature is 77 degree C and the FPGA temperature is 58 degree C.

    These temperatures are well below the ADC12D1000 maximum allowed operating junction temperature of +140C.

    2) If the ADC LVDS outputs are active due to the self-clocking behavior, it is reasonable to expect the FPGA circuitry to be active and dissipating some amount of power. You will need to work with Xilinx to confirm whether 67 degrees C is expected, and acceptable or not.

    If you are still having issues getting the LMX2581 operating as needed I recommend you create a new thread post here: http://e2e.ti.com/support/rf__digital_radio/high_performance_rf_modulators_pll_and_vco_products/f/224.aspx

    Regards,

    Jim B

  • 0 in reply to Jim Brinkhurst1
    Intellectual 275 points

    Hi Jim,

    Thank you for your reply.

    As of now I am driving the ADC in Power down mode and hence the the temperature is normal.

    I am still not getting the output at LMX2581 clock synthesizer and I have put the query regarding the issue.

    I have also discussed with xilinx and the temperature is acceptable.

    They have suggested some settings at FPGA side to reduce the temperature. I will implement it to see any difference in device temperature.

    Regards,

    Amit K Bhat

  • 0 in reply to Amith Bhat
    TI__Mastermind 43830 points

    Hi Amit

    Please let me know if you have resolved these issues with the ADC12D1000 and LMX2581.

    If everything is working now I would like to close this issue. If you still need help please let us know the current status.

    Regards,

    Jim B