64 feet and less than 64 feet of STM32 for ad attention, refer to power handling methods

Source: 64 feet and less than 64 feet of STM32 for ad attention, refer to power handling methods

Note that there is no internal reference on the ADC_IN17, which is said to be the wrong concept of the reference voltage.

So the line below the understanding is not right, if it is a reference, then its voltage is assumed to be 1.2V calculation, the actual measured digital amount is 1271~1275, according to this projection: 1.2/1275=vdd/4095, so vdd=3.85v, It is obvious that the value of the voltage conversion is inconsistent with the actual 3.3V, so it is not useful as a reference. In fact, the voltage of a reference source can be collected by Universal adc_in1, and other channels are scaled accordingly. The----------------------------------------------------------------adc_in17 is an internal reference voltage, not a reference voltage; it is only equivalent to a standard voltage reference.

The internal reference voltage of the STM32 Vrefint is connected to the ADCX_IN17, which acts as a standard voltage measurement point, and the internal reference voltage Vrefint can only be used in the main ADC1. The internal reference voltage Vrefint is not the same as the reference voltage. The reference voltage of the ADC is provided by the vref+ and serves as the reference voltage for the ADC converter. When we use the vref+ directly from the VCC voltage, when the VCC voltage fluctuation is relatively large or the regulator performance is poor, the internal reference voltage of the STM32 can be used to vrefint correct the measurement accuracy. To measure the voltage value of 1 channels For example, read the ADC measurement results of the reference voltage first, recorded as Adre, and then read the ADC conversion results to measure Channel 1, recorded as ADch1; the voltage to be measured is: Vch1 = vrefint* ((adch1* (vref/4096))/ (adre* (vref/4096))) Note: Vrefint=1.2v,vref is simplified for the reference voltage value =3.3v Formula: Vch1 = vrefint* (Adch1/adre) This method is equivalent to the internal reference voltage Vrefint as the ADC reference voltage, that is, the accuracy of the VREF reference voltage has not affected the results, the ADC conversion results are basically determined by the accuracy of vrefint. Note: In general, this method is only suitable for use when the vref+ reference voltage (in fact, the VCC voltage) is too discrete. We know that the STM32 in the 64 feet and less than 64 feet of the model, vref+ in the chip and the VCC signal line connected to the chip, so that the reference voltage of the ad is VCC voltage, then we can use a high precision external reference voltage, and then using the above method, It may be possible to solve the problem of inaccurate ADC measurements due to low accuracy of the VCC supply voltage.

64 feet and less than 64 feet of STM32 for ad attention, refer to power handling method (RPM)