Analog input frequency to ADuC7026

What is the maximum analog input frequency ADuC7026 can handle? Im planning to use frequency range of 1 MHz- 15 MHz for my system? Will ADuC7026 work fine in this frequency range?

  • Hi,

    It depends on what you're trying to do.

    The ADuC7026 can sample at a maximum rate of 1MSPS, so while it will sample signals in the range of 1MHz -15MHz fine, you will not be able to recreate the original signal.

    In order to recreate the original signal, you need to sample at least twice as fast as the highest frequency component of the signal.

  • Hi Rithura,

    ADuC7026 is not good for your frequency range.

    It COULD sample at 1 MSPS, but if someone tries to get ALL available 12 ADC channels at this frequency - bad lack.

    It CAN sample and put them into ADC registers, but then it has to do something with the data, at least put them into memory buffer and do calculations or other things, and simply by filling the memory buffer it has little bandwidth left for the processing of the data.

    Note: it does not have DMA to transfer data from ADC registers to memory buffer. If you need to send or read something out via SPI or UART, it does not have FIFO, so CPU has to do all job.

    ADuC7126 is slightly better but still has limits and problems.

    Igor

  • Hi Igor,

    thanks for ur detailed reply. Im trying to convert my data to dc level first and then feed it to ADuC7026. Do u think that will solve my problem? Actually Im not using all the 12 ADC inputs. i have to use just channel 0 and channel 1. What i wanted was to simultaneously sample them, buut since it has a single ADC, i am ok with that. My main concern was that I was giving 1- 15 MHz frequency signal to my DUT whose output was supposed to go to ADC of ADuC7026. But now im thinking of doing some signal conditioning so that i get two dc voltages which i can give to ADC of Microcontroller.

    I cant change the controller as i have already ordered its evaluation board. Do u think my this arrangement will solve my problem?

    Ritula

  • Ritula,

    You did not clearly say what IS the problem.

    Reading DC voltages via ADC is not a problem.

    Of cause, you need to put LPF 2-3rd order between signal and ADC input.

    For qusi-DC, It can be simple R-C-R-C or buffered with OPAm. The cutoff filter frequency should be chosen based on max frequency you want to measure.

    NOTE: the ADC is only 12 bits - is it enough for you? it can distinguish 3.3V / 4096 = 0.81 mV per bit. (or smaller, 0.61 mV, if you use internal 2.5V ref instead of 3.3V)

    It is possible to oversample, say, 16 times, average 16 samples - you would get (theoretically) 14 bits resolution.

    But in order average to work , signal should have SOME noise more than 1 bit, say, 1-2 mV

    Igor