I am using the built-in ADC of Renesas S5D9 microcontroller.

I am setting the ADC clock frequency to 60 MHz and a 12-bit resolution.

I am getting the samples, but I want to know at what sampling frequency it is being sampled.

Formula conversion time = ADC CLOCK period * bits being converted = (1/60MHz)* 12 = 0.2 microseconds

Is my understanding correct ?


1 Answer 1


The ADC conversion time and the sampling period are not the same. You can find the ADC conversion time in the datasheet of Renesas S5D9 microcontroller, page 90: https://www.renesas.com/eu/en/doc/products/renesas-synergy/doc/r01ds0303eu0130-synergy-s5d9.pdf

  • \$\begingroup\$ sampling frequency = 1/conversion time,with the above formula for converison time ,I am getting 0.2 microsec,In the datasheet its 0.4 microsec,Please correct me in the above formula or is it completely different for conversion time calculation? \$\endgroup\$
    – Kian
    Commented Sep 8, 2020 at 12:05
  • \$\begingroup\$ This formula is not considering the number of channels in the ADC unit. \$\endgroup\$
    – Yiftah
    Commented Sep 8, 2020 at 12:15
  • \$\begingroup\$ Also, I don't know much about ADC HW architectures, but assuming every bit takes one clock cycle seems unreasonable. I would just use the conversion time value specified in the datasheet. \$\endgroup\$
    – Yiftah
    Commented Sep 8, 2020 at 12:21
  • \$\begingroup\$ ADC has 2 units,unit0 with 13,unit1 with 11 so total 24 channels.what adc frequency needs to be set to get converson time of 0.01msec. \$\endgroup\$
    – Kian
    Commented Sep 8, 2020 at 12:32

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