模拟多路复用器的当前限值是多少？

嗨，迈克，
1）我不确定是什么导致呼吸压力模拟输入和参考电压之间的交叉耦合。尝试的方法之一是使用一个缓冲区（一个单位增益PGA或电压跟随器）在传感器的输入，然后把它应用到比较器。
2）电压低于VDDA可输入模拟多路复用器。你能详细说明放电电阻器是什么吗？
3）用抖动的方法增加DAC的分辨率，VDAC的数据源已被选为“DAC的客车，但只有1的DAC的总线，因此多VDACS不能有独立的硬件数据来源。



     以下为原文
  Hi Mike,
     
    1) I am not sure what is causing cross-coupling between the breath pressure analog input and the reference voltages. One method to try out would be to use a buffer (a unity gain PGA or Voltage Follower) at the sensor input before applying it to the comparator.
     
    2) Voltage less than Vdda can be applied as input to the Analog Mux. Can you please elaborate on what discharge resistor is?
     
    3) To use dithering method to increase the resolution of the DAC, the data source of the VDAC has to be chosen as 'DAC Bus', but there is only 1 DAC bus, hence multiple VDACs cannot have independant hardware data sources.

嗨，谢谢你的回复，这里有一些澄清：
1。呼吸的压力传感器进入了PGA块已经。这是进入comparitors锯齿波电压和参考电压的comparitor似乎靠呼吸压力电压的影响。所以我不确定我会尝试缓冲哪个信号。
2。我实际上使用复用作为一个承载电流的开关（也许这不是应该做的，因为我发现我无法路由的DAC输出直接复用；我不得不路线了引脚然后连接到另一个引脚的路线回到MUX。我目前正在使用的2个DAC，一个锯齿集成电容器的充电和放电这一。为了提高频率分辨率，我想一起使用2个DAC的充电（使用不同的电流范围为EAC）然后通过电阻放电。但是，如果电阻太小，则电流可能太高。这是设计违反了该芯片的限制？
谢谢
-迈克



     以下为原文
   Hi, thanks for the reply, here's some more clarifications:
    1.  The breath pressure sensor is going into a PGA block already.  It's the sawtooth voltage that is going into the comparitors and it's the comparitor reference voltages that seem to be getting affected by the voltage on the breath pressure.  So I'm not sure which signal I would try to buffer.
    2.  I'm actually using the Mux as a current-carrying switch (maybe this isn't supposed to be done, since I noticed that I couldn't route the DAC outputs directly to the Mux; I had to route it out to pins and then connect to another pin to route back to the Mux.  I am currently using 2 DAC's, one to charge the sawtooth integration capacitor and one to discharge it.  In order to increase frequency resolution, I was thinking to use the 2 DAC's together to charge it (using different current r ranges for eac) and t hen discharge it through a resistor.  But if the resistor is too small, then the current may be too high.  Or is this design a violation of the restrictions of the chip?
    Thanks
    -Mike

嗨，迈克，
1）你能告诉我们什么是比较器的参考吗？如果它是分压器，则必须确保其连接的接地应该与高载流路径隔离。否则将有两点之间的串扰。
2）同时，为了减少串扰，你可以保持管脚（呼吸压力传感器输入和参考）相距甚远（至少不是一个靠近另一个）。
3）您无法通过模拟多路复用器路由，因为您必须选择硬件模拟多路复用器。硬件多路复用器要求输入通道连接到引脚。如果您选择软件模拟多路复用器，那么您可以直接连接DAC而不需要任何引脚。可以使用API来选择通道。
4）你使用VDAC还是IDAC给电容充电？如果需要对称波形，那么建议使用单个IDAC分别对电容器充电和放电（分别使用源和汇）。



     以下为原文
  Hi Mike,
     
    1)Can you please tell what is used as a reference for the comparator? If it is a voltage divider, then it must be ensured that the ground which it is connected to should be isolated from high current carrying paths. Else there will be cross-talk between two points.
    2) Also, to reduce the cross talk, you can keep the pins (Breath pressure sensor input and reference) far apart (atleast not one beside the other).
    3) You were not able to route through the analog mux because you must have chosen Hardware Analog Mux. Hardware Mux requires that the input channels be connected to pins. If you choose Software Analog Mux, then you can connect DAC directly without any Pin in between. You can use APIs to select the channel.
    4) Are you using VDAC or IDAC to charge the capacitor? If you need symmetric waveform, then it would be advisable to use the single IDAC to both charge and discharge the capacitor (using source and sink respectively).

使用IDAC充电电容将导致线性波形。
如果使用VDAC，它将不是线性的，因为与VDAC组件相关联的电阻器。
如果使用两个IDAC，一个用于充电，另一个用于放电，然后IDAC的电流能力略有变化（这并不少见），那么将在电容器上积累剩余电荷，这可能会产生偏移。



     以下为原文
  Charging capacitor using IDAC will result in linear waveform.
    If VDAC is used, it will not be linear because of the resistor associated with the VDAC component.
     
    If two IDACs are used, one for charging and other for discharging, then slight variation in the current capability of the IDACs (which is not uncommon), then there will be accumulation of residual charge on the capacitor which might bring about an offset.

您好!
我将讨论你在前面一个问题中提到的DAC抖动问题。这是正确的，DAC总线只是一个必须在4个DAC块之间共享。但是你要明白，DAC的总线数据总线可以复用到4 DAC模块与选通信号的使用。
如果你想使用同一总线上多个数模转换器DAC可以有不同的数据来对DAC的公共汽车但对应的输入数据选通在获得精确时间点的DAC。这个你可以在DAC元件使用外部选通信号。



     以下为原文
  Hi
    I would discuss about the dithering of the DAC you talking about in one of the previous questions. It is right that the DAC bus is just one that has to be shared between 4 DAC blocks. But you have to understand that the DAC bus is a data bus can be multiplexed onto the 4 DAC blocks with the use of strobe signal.
    If you would want to use the same DAC bus on multiple DACs you can have different data coming on the DAC bus but the DAC corresponding to the incoming data getting strobed at the exact point of time. For this you can use the external strobe signal in the DAC component.

嗨，谢谢你的额外信息。
对于比较器，其中一个是使用1.024V作为“参考”，另一个是使用VDDA／2作为“参考”和电容斜坡电压。VDDA／2参考电压正从其他无关输入改变。我有我的完整设计文件和示意图上传，如果你想参考他们（触摸敏感记录仪）。我不知道如何将它的接地与其他的隔离，并且我不认为呼吸模拟应该是一个高电流信号（虽然它进入PGA也使用VDDA／2作为它的参考电压），除非我的设计有问题。我尝试使用不同的模拟输入引脚，但它未能路由设计。
我使用IDAC来对电容器充电/放电，我确实得到了预期的线性斜坡。我不能使用相同的一个放电和充电，因为方向标志只能由软件而不是硬件设置，我使用硬件逻辑来切换充电和放电，以尽量减少量化误差。
谢谢，
-迈克



     以下为原文
   Hi, thanks for the extra info.  
    Regarding the comparitors, one of them is using 1.024V as the '-' reference and the other is using Vdda/2 as '-' reference and the capacitor ramp voltage.  It's the Vdda/2 reference voltage that's changing from the other unrelated input changing.  I do have my complete design files and schematics uploaded if you would like to refer to them (Touch-sensitive recorder).  I'm not sure how to isolate its ground from the other ones, and I don't think the breath analog in should be a high-current signal (though it is going into a PGA that also uses Vdda/2 as its reference voltage), unless I have a problem with my design.  I did try using a different analog input pin but then it failed to route the design.
     I am using IDAC's to charge/discharge the capacitor, and indeed I do get the expected linear ramp.  I can't use the same one for both discharge and charge since the direction flag is only settable by software and not hardware and I'm using hardware logic to toggle between charge and discharge in order to minimize quantization errors.
    Thanks,
    -Mike

嗨，只是一点点跟进信息。我做了一个测试使用板上锅电压作为比较器电压，它似乎照顾这个问题。所以至少现在，我认为这是足够好的，只要壶不被撞倒！
谢谢，
-迈克



     以下为原文
  Hi, just a bit of followup info.  I did a test using the on-board pot voltage as the comparator voltage, and it seems to take care of the problem.  So at least for now, I think that's good enough, as long as the pot doesn't get bumped!
     
    Thanks,
    -Mike