Multi Channel ADC + DMA on STM32F723. Conversion of one channel affects other channels

Hello ST Community,

as part of a project I want to perform an AD conversion (ADC1 + DMA) of 4 channels at a sampling frequency of 5.5kHz. For this I have configured a timer which determines the sampling frequency and the data is stored on a MicroSD card.

The MCU is the STM32F723IC. I generate a PWM signal on one channel between 0-3.3V at 1 Hz and 50% duty cycle on the ADC CH1 and notice that the other three channels show a "weakened" pattern.

While cross-talk like behavior is displayed, the fact that when splitting the channels on two ADCs (ADC1 CH1 + CH2 and ADC2 CH3 + CH4) this pattern is only present on CH2 which leads me to suspect that the SAR ADC's capacitor is not discharging quickly. How can I prevent the pattern from appearing on the other pins when using a single ADC with 4 channels and the described sampling frequency? The pins are directly routed out from the processor. Floating state, no filtering is used.

Attached is a code snippet of the relevant parts:

...
	htim5.Instance = TIM5;
	htim5.Init.Prescaler = 0;
	htim5.Init.CounterMode = TIM_COUNTERMODE_UP;
	htim5.Init.Period = 19593;
	htim5.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
	htim5.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
	HAL_TIM_RegisterCallback(&htim5, HAL_TIM_BASE_MSPINIT_CB_ID, Microphones_TIM_Base_MspInit);
	HAL_TIM_RegisterCallback(&htim5, HAL_TIM_BASE_MSPDEINIT_CB_ID, Microphones_TIM_Base_MspDeInit);
	if (HAL_TIM_Base_Init(&htim5) != HAL_OK)
	{
		Error_Handling();;
		return status;
	}
	sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
	if (HAL_TIM_ConfigClockSource(&htim5, &sClockSourceConfig) != HAL_OK)
	{
		Error_Handling();
		return status;
	}
	sMasterConfig.MasterOutputTrigger = TIM_TRGO_UPDATE;
	sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
	if (HAL_TIMEx_MasterConfigSynchronization(&htim5, &sMasterConfig) != HAL_OK)
	{
		Error_Handling();
		return status;
	}
 
	ADC_ChannelConfTypeDef sConfig = {0};
 
	/** Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion) */
	hadc1.Instance = ADC1;
	hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
	hadc1.Init.Resolution = ADC_RESOLUTION_12B;
	hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;
	hadc1.Init.ContinuousConvMode = DISABLE;
	hadc1.Init.DiscontinuousConvMode = DISABLE;
	hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_RISING;
	hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T5_TRGO;
	hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
	hadc1.Init.NbrOfConversion = NBR_MICROPHONES_CHANNELS;
	hadc1.Init.DMAContinuousRequests = ENABLE;
	hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
	HAL_ADC_RegisterCallback(&hadc1, HAL_ADC_MSPINIT_CB_ID, Microphones_ADC_MspInit);
	HAL_ADC_RegisterCallback(&hadc1, HAL_ADC_MSPDEINIT_CB_ID, Microphones_ADC_MspDeInit);
	if (HAL_ADC_Init(&hadc1) != HAL_OK)
	{
		Error_Handling();
		return status;
	}
	HAL_ADC_RegisterCallback(&hadc1, HAL_ADC_CONVERSION_COMPLETE_CB_ID, Microphones_ADC_ConvCpltCallback);
 
	/** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	 */
	sConfig.Channel = ADC_CHANNEL_15;
	sConfig.Rank = ADC_REGULAR_RANK_1;
	sConfig.SamplingTime = ADC_SAMPLETIME_480CYCLES;
	if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	{
		Error_Handling();
		return status;
	}
	/** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time. */
	sConfig.Channel = ADC_CHANNEL_9;
	sConfig.Rank = ADC_REGULAR_RANK_4;
	if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	{
		Error_Handling();
		return status;
	}
	/** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	 */
	sConfig.Channel = ADC_CHANNEL_7;
	sConfig.Rank = ADC_REGULAR_RANK_8;
	if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	{
		Error_Handling();
		return status;
	}
	/** Configure for the selected ADC regular channel its corresponding rank in the sequencer and its sample time.
	 */
	sConfig.Channel = ADC_CHANNEL_5;
	sConfig.Rank = ADC_REGULAR_RANK_12;
	if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
	{
		Error_Handling();
		return status;
	}
 
	HAL_StatusTypeDef halStatus = HAL_OK;
 
	halStatus = HAL_TIM_Base_Start_IT(&htim5);
	if(halStatus != HAL_OK)
	{
		Error_Handling();
		return status;
	}
 
	halStatus = HAL_ADC_Start_DMA(&hadc1, (uint32_t*)&tempBuffer[0], NBR_MICROPHONES_CHANNELS);
	if(halStatus != HAL_OK)
	{
		Error_Handling();
		return status;
	}

 If some parts of the source code are missing, I can provide them.