I am currently using LTC2311 as ADC with CMOS setting in my circuit. However, I cannot seem to get any output out in the microcontroller (I use the STM32 Nucleo development board). My question is that

  1. In the datasheet, it is mentioned that to start the conversion the CNV pin needs to be triggered by a low jitter pulse of 38.1ns to achieve the maximum rate of conversion.
  • What is the most effective way to send the CNV signal ? should it be done by the usual GPIO pin or with the pin specially assigned for chip select
  1. For the clock signal, it is mentioned that

The falling edge of this clock shifts the conversion result MSB first onto the SDO pins. A 105MHz external clock must be applied at the SCK pin to achieve 5Msps throughput.

  • I am currently using the microcontroller's internal clock of 48MHz. Does this affect the data that is sent? I am aware that this changes the data sampling rate, but apart from that is there any effect on the output?
  • is there any better way to generate a clock signal for the output? if so, how?

Thank you so much for your help, It will help with my thesis so much.

  1. CNV pin does not need precsion to achieve maximum rate, but it needs precision to achieve minimum jitter, i.e. to sample at precice intervals.

It depends on what your precision needs are, but just to get you started, use a GPIO pin. It can be a GPIO pin or the Chip Select pin, but it depends on if you use hardware or software controlled Chip Select to begin with. The STM32 does not care about Chip Select state when it is master. If you want precision, to sample at exactly uniform intervals, perhaps you would like to use a timer output channel pin so you can use a hardware timer for accurate sampling intervals.

  1. If your STM32 MCU is running at 48 MHz, most likely highest clock you can use with the SPI peripheral is 24 MHz. So it will limit your bit transfer speed. However, you did not mention which STM32 so you better check yourself what clock frequencies it can use, and which SPI frequencies are possible with that clock frequency.

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