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MSP ADC conversion rate

bongyong choi
Prodigy 30 points

Other Parts Discussed in Thread: MSP430I2041

Hi!

I'm using MSP430i2041 for my project and want to upgrade to MCU which has higher ADC sampling rate, and data memory, but also can do ADC simultaneously at least 4 port just as i2041.

so, I've found MSP430F5x/6x series at ti homepage and that the CLOCK of Sigma-Delta 24 is 1.024 Mhz for best conversion and about 2 Mhz maximum.

My question is

1. Is there MSP which has higher CLOCK rate of Sigma-Delta ADC than 1.024Mhz for accurate ADC result.

2. if not, should i use SAR ADC or lower resolution (ex. SD24 -> SD16) for faster ADC .

please answer me~!

thank you

  • 0
    Guru 320650 points
    The ADC clock is not the same as the sample clock.

    What sample rate, and what accuracy, do you actually need?
  • 0 in reply to Clemens Ladisch
    Prodigy 30 points
    In msp430i user guide, f_M ( Modulator frequency ) is 1.024 Mhz and f_s ( Sample frequency) is f_M/OSR.

    I thought that Sample Per Second (SPS) equals f_s, and the MSP having a faster f_M can do ADC fastly.

    So I need a higher f_M to get a faster SPS than msp430i2041 or another way, when do simultaneously four conversion.

    Thank you.
  • 0 in reply to bongyong choi
    Guru 46710 points

    Most of msp430 have single SAR ADC, thus requirement "four simultaneous conversions fastly, faster than SD ADC" cannot be met. 

    It is paramount for you to specify sample rate and maybe application too, because possibly you can live with sequential conversions using SAR ADC.

  • 0 in reply to Ilmars
    Prodigy 30 points
    Thank you for replying, then I should use SD ADC.

    Actually, My project is better if MCU can do ADC faster.

    So, Now I could search that SD24_B's max modulator clock is 2.3 Mhz and it is fastest in TI's MSP series.

    Is it correct??
  • 0 in reply to bongyong choi
    Guru 46710 points
    >So, Now I could search that SD24_B's max modulator clock is 2.3 Mhz and it is fastest in TI's MSP series.
    Well, you shall note that clock frequency is not ADC samplerate. For example at OSR=1024 and 2.3 MHz clock SD24 have 2256 samples/sec output while ADC10 SAR ADC can have 200000 samples per second output. Do the math :)

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