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TLC0838转换问题。

Other Parts Discussed in Thread: TLC0838, ADS7868

用TLC0838设计了一款直流电压测量电路,发现转换的数据不稳定;
1、差分输入,没有用到com脚,直接接地了,数字地、模拟地还有com脚都接到一起了;疑问:com脚应该怎么连接?
2、spi接口速率40kHz;
3、用SE脚控制AD结果输出;
4、用示波器观察了DO和CLK的对比波形;发现:AD的结果(DO)不稳定,跳动的厉害,一会大一会儿小;在有些特殊的输入点,比如2.8v左右,输出就变成0了;此时在高位(MSB)有宽度不够的毛刺;
5、有哪位大侠能指导我一下;怎么接线?
  • 见手册第3页

    The common input on the TLC0838 can be used for a pseudodifferential input. In this mode, the voltage on the
    common input is considered to be the negative differential input for all channel inputs. This voltage can be any
    reference potential common to all channel inputs.

    这个器件太老了.你用新一些的吧;EG:ADS7868, etc...

  • 读数不稳,主要是由于REFERENCE电压不稳,或者有noise,或者输入端阻抗设计不当或者PCB设计不当的问题。既然TI的工程师不建议用此款芯片,就改用其他们推荐的吧。