MCU's ADC sampling error

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MCU's ADC sampling error [Copy link]

 

How can the chip collect 3-phase current and 6-channel PWM signals at the same time when it only has 2 channels of AD sampling signals? How can the error be compensated?

maychang

"How to simultaneously collect 3-phase current and 6-channel PWM signals with only 2-channel AD sampling signals?"

Then AD can only be used in time-sharing mode. The three-phase current signals are connected to AD in turn by analog switches and converted separately.

maychang

How to compensate for errors?

I don't quite understand what the host means.

chunyang

PWM signals do not require ADC and can be read using regular IO.

The two-channel ADC can only collect three-channel analog signals in time-division multiplexing, and whether it can be used in this way needs to be determined according to the application requirements and ADC parameters. It should also be noted that many MCUs only have one built-in ADC, but they have two or more ADC inputs through the switching of the on-chip analog switch, which is a completely different concept from multi-channel ADC, so please pay attention to the distinction.

As for error compensation, let’s first clarify what the error is. If it is a conversion error of the ADC itself, it cannot be compensated.

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chunyang posted on 2020-8-31 15:26 PWM signals do not require ADC and can be read using conventional IO. Two ADCs can only collect three analog signals in time-division multiplexing, which needs to be determined based on application requirements and ADC parameters...

I just want to collect three current signals at the same time. Time-division multiplexing will definitely cause sampling errors. For example, RH850 and TMS570 seem to have two ADCs. The third channel will have errors. How to compensate for this error? I am a little confused about the MCU's built-in ADC switching to multiple channels. For example, TI's 2812 and 28335 can switch from one channel to two channels. Then can they only collect one signal at a time?

chunyang

The best debt was published on 2020-8-31 16:56 I just want to collect three current signals at the same time. Time-division multiplexing will definitely cause sampling errors. For example, RH850 and TMS570 seem to have two ADCs...

Then can you first explain why "time-division multiplexing will definitely result in sampling errors"?

freebsder

In some application scenarios, two-phase current can be used to calculate three-phase current. It depends on what you are driving. Please search Baidu for details.