NUCLEO-H723ZG ADC Accuracy

[sreyas40]

I'm currently using single 16-bit ADC, my requirement is to have ADC conversion error less than 1mV.

I'm using the ADC with DMA. I'm a beginner, currently getting 1-2mV error and it is not constant too. 

#define SCALE (3300.0f/65535.0f)

uint16_t adc_val = 0;

uint16_t ADC_ARR[5];



void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *hadc){

adc_val = ADC_ARR[0]*SCALE;

}

HAL_ADCEx_Calibration_Start(&hadc1, ADC_CALIB_OFFSET_LINEARITY, ADC_SINGLE_ENDED);

HAL_ADC_Start_DMA(&hadc1, (uint32_t*)ADC_ARR,1);

Also the ADC clock is derived from HSI  

[sreyas40]

Can you tell me/ a link to video on how to use VREFINT.

[MasterT]

There is no special about ST, it simply uses SAR architecture of the ADC. It may be not properly articulated  in the DS, but SAR requires very low impedance over High Frequency bandwidth presented at its inputs.

Look this thread 

My own experience with nucleo-H743zi2 tells that differential mode has much lower error than SE. You can get CAD files of the board, and trace pins down to connectors, the best if two wires of the diif input runs in parallel. Usually I used PC2-PC3 or PA6-PA7 - likely same for H723.

[sreyas40]

Using VREFINT didn't help, maybe i will also try with external reference voltage

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file           : main.c
  * @brief          : Main program body
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2025 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */

/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
ADC_HandleTypeDef hadc1;
ADC_HandleTypeDef hadc3;
DMA_HandleTypeDef hdma_adc1;
DMA_HandleTypeDef hdma_adc3;

DAC_HandleTypeDef hdac1;

/* USER CODE BEGIN PV */
#define BUFLEN 10000
#define vref_cal *VREFINT_CAL_ADDR
int vref=0;
int ref_c=0;
#define SCALE (3300.0f/65535.0f)
uint16_t vref_raw = 0;
uint16_t adc_val = 0;
uint16_t ADC_ARR[5];
uint16_t ADC_ARR_ref[5];
float voltage;
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
void PeriphCommonClock_Config(void);
static void MPU_Config(void);
static void MX_GPIO_Init(void);
static void MX_DMA_Init(void);
static void MX_ADC1_Init(void);
static void MX_ADC3_Init(void);
static void MX_DAC1_Init(void);
/* USER CODE BEGIN PFP */

/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef *hadc){

	if(hadc->Instance == ADC1){
	adc_val = ADC_ARR[0];
	voltage = ADC_ARR[0]*vref/65535;
	}
	if(hadc->Instance == ADC3){
		vref_raw = ADC_ARR_ref[0];
		vref = 3300*vref_cal/vref_raw;
	}

}

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MPU Configuration--------------------------------------------------------*/
  MPU_Config();

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* Configure the peripherals common clocks */
  PeriphCommonClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_DMA_Init();
  MX_ADC1_Init();
  MX_ADC3_Init();
  MX_DAC1_Init();
  /* USER CODE BEGIN 2 */
  HAL_ADCEx_Calibration_Start(&hadc1, ADC_CALIB_OFFSET_LINEARITY, ADC_SINGLE_ENDED);
  HAL_ADCEx_Calibration_Start(&hadc1, ADC_CALIB_OFFSET, ADC_SINGLE_ENDED);
  HAL_ADC_Start_DMA(&hadc1, (uint32_t*)ADC_ARR,1);
  HAL_ADC_Start_DMA(&hadc3,ADC_ARR_ref,1);
  HAL_DAC_Start(&hdac1, DAC_CHANNEL_1);
  HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R , 1240);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
//	  HAL_ADCEx_Calibration_Start(&hadc1, ADC_CALIB_OFFSET, ADC_SINGLE_ENDED);
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Supply configuration update enable
  */
  HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);

  /** Configure the main internal regulator output voltage
  */
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

  while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_DIV1;
  RCC_OscInitStruct.HSICalibrationValue = 64;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
  RCC_OscInitStruct.PLL.PLLM = 4;
  RCC_OscInitStruct.PLL.PLLN = 12;
  RCC_OscInitStruct.PLL.PLLP = 1;
  RCC_OscInitStruct.PLL.PLLQ = 4;
  RCC_OscInitStruct.PLL.PLLR = 2;
  RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_3;
  RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
  RCC_OscInitStruct.PLL.PLLFRACN = 0;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2
                              |RCC_CLOCKTYPE_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV2;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV2;
  RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV2;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief Peripherals Common Clock Configuration
  * @retval None
  */
void PeriphCommonClock_Config(void)
{
  RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};

  /** Initializes the peripherals clock
  */
  PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_ADC;
  PeriphClkInitStruct.PLL2.PLL2M = 4;
  PeriphClkInitStruct.PLL2.PLL2N = 12;
  PeriphClkInitStruct.PLL2.PLL2P = 4;
  PeriphClkInitStruct.PLL2.PLL2Q = 2;
  PeriphClkInitStruct.PLL2.PLL2R = 2;
  PeriphClkInitStruct.PLL2.PLL2RGE = RCC_PLL2VCIRANGE_3;
  PeriphClkInitStruct.PLL2.PLL2VCOSEL = RCC_PLL2VCOWIDE;
  PeriphClkInitStruct.PLL2.PLL2FRACN = 0;
  PeriphClkInitStruct.AdcClockSelection = RCC_ADCCLKSOURCE_PLL2;
  if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
}

/**
  * @brief ADC1 Initialization Function
  *  None
  * @retval None
  */
static void MX_ADC1_Init(void)
{

  /* USER CODE BEGIN ADC1_Init 0 */

  /* USER CODE END ADC1_Init 0 */

  ADC_MultiModeTypeDef multimode = {0};
  ADC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN ADC1_Init 1 */

  /* USER CODE END ADC1_Init 1 */

  /** Common config
  */
  hadc1.Instance = ADC1;
  hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
  hadc1.Init.Resolution = ADC_RESOLUTION_16B;
  hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc1.Init.LowPowerAutoWait = DISABLE;
  hadc1.Init.ContinuousConvMode = ENABLE;
  hadc1.Init.NbrOfConversion = 1;
  hadc1.Init.DiscontinuousConvMode = DISABLE;
  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc1.Init.ConversionDataManagement = ADC_CONVERSIONDATA_DMA_CIRCULAR;
  hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc1.Init.LeftBitShift = ADC_LEFTBITSHIFT_NONE;
  hadc1.Init.OversamplingMode = DISABLE;
  hadc1.Init.Oversampling.Ratio = 1;
  if (HAL_ADC_Init(&hadc1) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure the ADC multi-mode
  */
  multimode.Mode = ADC_MODE_INDEPENDENT;
  if (HAL_ADCEx_MultiModeConfigChannel(&hadc1, &multimode) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_3;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_387CYCLES_5;
  sConfig.SingleDiff = ADC_SINGLE_ENDED;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 2474;
  sConfig.OffsetSignedSaturation = DISABLE;
  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ADC1_Init 2 */

  /* USER CODE END ADC1_Init 2 */

}

/**
  * @brief ADC3 Initialization Function
  *  None
  * @retval None
  */
static void MX_ADC3_Init(void)
{

  /* USER CODE BEGIN ADC3_Init 0 */

  /* USER CODE END ADC3_Init 0 */

  ADC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN ADC3_Init 1 */

  /* USER CODE END ADC3_Init 1 */

  /** Common config
  */
  hadc3.Instance = ADC3;
  hadc3.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
  hadc3.Init.Resolution = ADC_RESOLUTION_12B;
  hadc3.Init.DataAlign = ADC3_DATAALIGN_RIGHT;
  hadc3.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc3.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc3.Init.LowPowerAutoWait = DISABLE;
  hadc3.Init.ContinuousConvMode = ENABLE;
  hadc3.Init.NbrOfConversion = 1;
  hadc3.Init.DiscontinuousConvMode = DISABLE;
  hadc3.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc3.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc3.Init.DMAContinuousRequests = ENABLE;
  hadc3.Init.SamplingMode = ADC_SAMPLING_MODE_NORMAL;
  hadc3.Init.ConversionDataManagement = ADC_CONVERSIONDATA_DMA_CIRCULAR;
  hadc3.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc3.Init.LeftBitShift = ADC_LEFTBITSHIFT_NONE;
  hadc3.Init.OversamplingMode = DISABLE;
  hadc3.Init.Oversampling.Ratio = ADC3_OVERSAMPLING_RATIO_2;
  if (HAL_ADC_Init(&hadc3) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_VREFINT;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC3_SAMPLETIME_247CYCLES_5;
  sConfig.SingleDiff = ADC_SINGLE_ENDED;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 0;
  sConfig.OffsetSign = ADC3_OFFSET_SIGN_NEGATIVE;
  if (HAL_ADC_ConfigChannel(&hadc3, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ADC3_Init 2 */

  /* USER CODE END ADC3_Init 2 */

}

/**
  * @brief DAC1 Initialization Function
  *  None
  * @retval None
  */
static void MX_DAC1_Init(void)
{

  /* USER CODE BEGIN DAC1_Init 0 */

  /* USER CODE END DAC1_Init 0 */

  DAC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN DAC1_Init 1 */

  /* USER CODE END DAC1_Init 1 */

  /** DAC Initialization
  */
  hdac1.Instance = DAC1;
  if (HAL_DAC_Init(&hdac1) != HAL_OK)
  {
    Error_Handler();
  }

  /** DAC channel OUT1 config
  */
  sConfig.DAC_SampleAndHold = DAC_SAMPLEANDHOLD_DISABLE;
  sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
  sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
  sConfig.DAC_ConnectOnChipPeripheral = DAC_CHIPCONNECT_DISABLE;
  sConfig.DAC_UserTrimming = DAC_TRIMMING_FACTORY;
  if (HAL_DAC_ConfigChannel(&hdac1, &sConfig, DAC_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN DAC1_Init 2 */

  /* USER CODE END DAC1_Init 2 */

}

/**
  * Enable DMA controller clock
  */
static void MX_DMA_Init(void)
{

  /* DMA controller clock enable */
  __HAL_RCC_DMA1_CLK_ENABLE();
  __HAL_RCC_DMA2_CLK_ENABLE();

  /* DMA interrupt init */
  /* DMA1_Stream0_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA1_Stream0_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA1_Stream0_IRQn);
  /* DMA2_Stream0_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(DMA2_Stream0_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(DMA2_Stream0_IRQn);

}

/**
  * @brief GPIO Initialization Function
  *  None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  /* USER CODE BEGIN MX_GPIO_Init_1 */

  /* USER CODE END MX_GPIO_Init_1 */

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();
  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOE_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOB, LED_GREEN_Pin|LED_RED_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LED_YELLOW_GPIO_Port, LED_YELLOW_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : B1_Pin */
  GPIO_InitStruct.Pin = B1_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  HAL_GPIO_Init(B1_GPIO_Port, &GPIO_InitStruct);

  /*Configure GPIO pins : LED_GREEN_Pin LED_RED_Pin */
  GPIO_InitStruct.Pin = LED_GREEN_Pin|LED_RED_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  /*Configure GPIO pins : STLK_VCP_RX_Pin STLK_VCP_TX_Pin */
  GPIO_InitStruct.Pin = STLK_VCP_RX_Pin|STLK_VCP_TX_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.Alternate = GPIO_AF7_USART3;
  HAL_GPIO_Init(GPIOD, &GPIO_InitStruct);

  /*Configure GPIO pin : LED_YELLOW_Pin */
  GPIO_InitStruct.Pin = LED_YELLOW_Pin;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(LED_YELLOW_GPIO_Port, &GPIO_InitStruct);

  /* USER CODE BEGIN MX_GPIO_Init_2 */

  /* USER CODE END MX_GPIO_Init_2 */
}

/* USER CODE BEGIN 4 */

/* USER CODE END 4 */

 /* MPU Configuration */

void MPU_Config(void)
{
  MPU_Region_InitTypeDef MPU_InitStruct = {0};

  /* Disables the MPU */
  HAL_MPU_Disable();

  /** Initializes and configures the Region and the memory to be protected
  */
  MPU_InitStruct.Enable = MPU_REGION_ENABLE;
  MPU_InitStruct.Number = MPU_REGION_NUMBER0;
  MPU_InitStruct.BaseAddress = 0x0;
  MPU_InitStruct.Size = MPU_REGION_SIZE_4GB;
  MPU_InitStruct.SubRegionDisable = 0x87;
  MPU_InitStruct.TypeExtField = MPU_TEX_LEVEL0;
  MPU_InitStruct.AccessPermission = MPU_REGION_NO_ACCESS;
  MPU_InitStruct.DisableExec = MPU_INSTRUCTION_ACCESS_DISABLE;
  MPU_InitStruct.IsShareable = MPU_ACCESS_SHAREABLE;
  MPU_InitStruct.IsCacheable = MPU_ACCESS_NOT_CACHEABLE;
  MPU_InitStruct.IsBufferable = MPU_ACCESS_NOT_BUFFERABLE;

  HAL_MPU_ConfigRegion(&MPU_InitStruct);
  /* Enables the MPU */
  HAL_MPU_Enable(MPU_PRIVILEGED_DEFAULT);

}

/**
  * @brief  This function is executed in case of error occurrence.
  * @retval None
  */
void Error_Handler(void)
{
  /* USER CODE BEGIN Error_Handler_Debug */
  /* User can add his own implementation to report the HAL error return state */
  __disable_irq();
  while (1)
  {
  }
  /* USER CODE END Error_Handler_Debug */
}

#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  *   file: pointer to the source file name
  *   line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t *file, uint32_t line)
{
  /* USER CODE BEGIN 6 */
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */

. I think one of the reason it didn't work for me maybe my ADC1 being 16bit and Vrefint channel read by 12-bit ADC 

[Ozone]

These are secondary points.

To achieve a sub-mV accuracy a highly stable Vref and Vdda are absolute requirements, besides of the ADC resolution. Having the ADC on the same die (silicon) as digital sections that switch dozens of milliamps with nanoseconds of transition time makes this impossible. ADCs on a digital chip are a compromise, you need to live with that.
If you require such high accuracy, use an external ADC, with the properly designed analog section. 

I am not a hardware designer, but opamp / ADC manufacturers like TI, Analog (and probably ST as well) have design guidelines freely available for this endeavour.

[LCE]

> I'm actually trying to read voltage peaks from photodetector, averaging might not be suitable for my case.

Do you need the exact peak voltage?

What's the voltage difference of the peaks compared to "idle / no-signal level" ?

Maybe a comparator would be more suited?

Or an amplifier before the ADC.

Anyway, isn't the H723 ADC 12-bit only?

[sreyas40]

Can you suggest me a ADC module that could do that, I need at least 2.5MSPS  and <1mV accuracy. That would be very helpful :)

[sreyas40]

yes i need exact peak voltage.

There is no fixed difference between peaks.

I don't think a comparator will be useful?

Currently i'm testing by sampling at different voltages( 0-3V)

The board has 2 16-bit ADC and 1 12-bit ADC

[Ozone]

I'm no hardware designer, I had to look it up - like you.

But from what I learned over the years, it seems you significantly understimate the impact of your requirements.

[TDK]

> I need at least 2.5MSPS  and <1mV accuracy

Go look on a site like Digikey and see if there are standalone ADC chips that meet these requirements.

[LCE]

So... I never tested these 16-bit ADCs, but from the datasheet values (H723) theoretically it might be possible to get your 1 mV accuracy at 2.5 MSPS.

I guess you refer the 1 mV to a full scale input of VDDA = VREF = 3.3 V, referred to GNDA = GND = 0 V ?

1 mV at 3.3 V FS at 16 bit resolution equals ~ 20 LSB , which is just about the error sum you get by datasheet and is about an ENOB of 12.

To get that, all the settings of the STM32 must be perfect, calibration must be performed before using the ADC.
And you should use a more stable clock source than HSI, so switch to HSE. The Nucleo gets its HSE from the STLink MCU - attention, this might be 8.333 MHz (not sure), maybe 8 MHz.

And I'm pretty sure that you need an analog ADC driver, some (relatively) high-slew-rate & high-drive op-amp with 3.3V-single-supply and RRIO. Add an RC low pass with ~ 50R / 100pF between op-amp and ADC input, both R&C as close as possible to the ADC pin.

But no guarantee that this will work!
Especially on a Nucleo-board, where the ADC input lines go long ways across the board.