topic MC33774 measurement issue in High Performance Analog Front End Interfaces

MC33774 measurement issue

tianxing — Fri, 26 Sep 2025 02:57:39 GMT

Hello ,I have some questions about MC33774 :

1.How long does it take to do application measurement with 18 cell terminal measurement and 8 AINX measurement? I want to know the the scan time. I looked up it in the datasheet found two times I don't know which one is right.

Application timed continuous and tappmeas

2.After send first capture command how long should we wait to read the measurement ready status? We send the read measurement command between two capture commands and wait about 18 ms to read measuremnt ready status .But it always not ready for the first time . We want to know why and we have to guarantee to get a ready result every time we read. I attached the logistic data file for this problem.

3.We used the BalPause funtion in application measurement When we send the first capture command set this bit to 1 .Then we send the second capture command and change it to 0. But we can only got the voltage data for the first measurement after that the data became invalid value(0x8000). We want to know why and how to fix this problem?

We have checked the time between we sent two capture commands. It is 40ms and it take 660ms to send the next pair of capture commands. Is it OK ?

The attachment file is the SPI data we captured with logisc analyzer for problem 2.

Please help us check it.

Thank you for taking your time help us with these problems.

Re: MC33774 measurement issue

tianxing — Fri, 26 Sep 2025 03:28:14 GMT

Add the attachment file.

Re: MC33774 measurement issue

guoweisun — Fri, 26 Sep 2025 07:20:29 GMT

tSCAN =240us

APP 读取结果是 0x8000，可能有一下几条原因：
1. ADC 没有使能，需要 ALLM_CFG. MEASEN = 1。

2. 两条 APP_Capture 指令之间的时间间隔没有满足最短时间要求。

a) 如果没有使用暂停均衡功能，则两条指令之间需要至少大于 16 次 SCAN 的时间。

b) 如果提前设置了暂停均衡时间，并且 Application 采样也启用了暂停均衡功能。需要保证两条【App_Capture 之间的时间间隔】 > 【暂停均衡时间】+【16 次 SCAN 时间】。

3. 两条 APP_Capture 之后，重复读取 App 的结果寄存器。只有第一次读取寄存器会返回正确结果，从第二次读取结果开始就是 0x8000。

4. 两条 App_Capture 之后，没有等待 265us 刷新寄存器时间，需要延迟足够时间再读取结果寄存器。

5. 两条 App_Capture 之间，将 ADC 停止运行，即中途将 ALLM_CFG. MEASEN =0。

Re: MC33774 measurement issue

tianxing — Fri, 26 Sep 2025 08:37:30 GMT

孙工，您好，感谢回复

按照您说的我计算了一下时间，检查了我们的读取动作，还没有发现问题。

关于这个问题我发送了逻辑分析仪的数据给艾瑞的贺工，如果方便的话还请您帮忙看看。

我会将程序简化看看只保留采样是不是就可以更新数据了，感谢支持