Question
STM32G474, AN5306 , OPAMP Timer controlled multiplexer mode feature, gain problem with secondary channel.
Hello, we intend to implement a time-dependent channel change via the operational amplifier in voltage follower mode, as described in AN5306 - Rev 1 Page 31, 5.1. However, when checking the output, there is an unwanted gain (x2) on channel 2. Any idea where it comes from or what could be set incorrectly?
Switching between channels using a timer and MUX works as expected, but the second channel has a gain of 2, although in voltage follower mode this should not be the case.
For testing, 1 volt was connected to both channels and it was expected that 1 volt would come out at the output, despite the change via the MUX, but it changes between 1 volt and 2 volts because the second channel has this unwanted gain.
CubeMX Configuration: OPA
Timer:
Pins:
code settings:
/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/** Configure the main internal regulator output voltage
*/
HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1_BOOST);
/** 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_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = RCC_PLLM_DIV4;
RCC_OscInitStruct.PLL.PLLN = 85;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
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_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_4) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief OPAMP6 Initialization Function
* None
* @retval None
*/
static void MX_OPAMP6_Init(void)
{
/* USER CODE BEGIN OPAMP6_Init 0 */
/* USER CODE END OPAMP6_Init 0 */
/* USER CODE BEGIN OPAMP6_Init 1 */
/* USER CODE END OPAMP6_Init 1 */
hopamp6.Instance = OPAMP6;
hopamp6.Init.PowerMode = OPAMP_POWERMODE_NORMALSPEED;
hopamp6.Init.Mode = OPAMP_FOLLOWER_MODE;
hopamp6.Init.NonInvertingInput = OPAMP_NONINVERTINGINPUT_IO2;
hopamp6.Init.InternalOutput = DISABLE;
hopamp6.Init.TimerControlledMuxmode = OPAMP_TIMERCONTROLLEDMUXMODE_TIM8_CH6;
hopamp6.Init.NonInvertingInputSecondary = OPAMP_SEC_NONINVERTINGINPUT_IO0;
hopamp6.Init.UserTrimming = OPAMP_TRIMMING_FACTORY;
if (HAL_OPAMP_Init(&hopamp6) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN OPAMP6_Init 2 */
/* USER CODE END OPAMP6_Init 2 */
}
/**
* @brief TIM8 Initialization Function
* None
* @retval None
*/
static void MX_TIM8_Init(void)
{
/* USER CODE BEGIN TIM8_Init 0 */
/* USER CODE END TIM8_Init 0 */
TIM_ClockConfigTypeDef sClockSourceConfig = {0};
TIM_MasterConfigTypeDef sMasterConfig = {0};
TIM_OC_InitTypeDef sConfigOC = {0};
TIM_BreakDeadTimeConfigTypeDef sBreakDeadTimeConfig = {0};
/* USER CODE BEGIN TIM8_Init 1 */
/* USER CODE END TIM8_Init 1 */
htim8.Instance = TIM8;
htim8.Init.Prescaler = 16999;
htim8.Init.CounterMode = TIM_COUNTERMODE_UP;
htim8.Init.Period = 99;
htim8.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim8.Init.RepetitionCounter = 0;
htim8.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
if (HAL_TIM_Base_Init(&htim8) != HAL_OK)
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim8, &sClockSourceConfig) != HAL_OK)
{
Error_Handler();
}
if (HAL_TIM_OC_Init(&htim8) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterOutputTrigger2 = TIM_TRGO2_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim8, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
sConfigOC.OCMode = TIM_OCMODE_TOGGLE;
sConfigOC.Pulse = 50;
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
sConfigOC.OCIdleState = TIM_OCIDLESTATE_RESET;
if (HAL_TIM_OC_ConfigChannel(&htim8, &sConfigOC, TIM_CHANNEL_6) != HAL_OK)
{
Error_Handler();
}
sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_DISABLE;
sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_DISABLE;
sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_OFF;
sBreakDeadTimeConfig.DeadTime = 0;
sBreakDeadTimeConfig.BreakState = TIM_BREAK_DISABLE;
sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
sBreakDeadTimeConfig.BreakFilter = 0;
sBreakDeadTimeConfig.BreakAFMode = TIM_BREAK_AFMODE_INPUT;
sBreakDeadTimeConfig.Break2State = TIM_BREAK2_DISABLE;
sBreakDeadTimeConfig.Break2Polarity = TIM_BREAK2POLARITY_HIGH;
sBreakDeadTimeConfig.Break2Filter = 0;
sBreakDeadTimeConfig.Break2AFMode = TIM_BREAK_AFMODE_INPUT;
sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_DISABLE;
if (HAL_TIMEx_ConfigBreakDeadTime(&htim8, &sBreakDeadTimeConfig) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN TIM8_Init 2 */
/* USER CODE END TIM8_Init 2 */
}
main.c
...
HAL_TIM_OC_Start(&htim8, TIM_CHANNEL_6);
HAL_OPAMP_Start(&hopamp6);
while(1)