Can PSOC4 be applied in thermal couple temperature device? Because of there is only 2 OP. We need to do the sample with differenctial mode.
Due to there is no VDC in PSOC4, so we need to use one IDAC and one OP for reference power. And then the there is no enough OP to amply differencial samples signals.
Hi Ben Jiang
1) Differential mode INS-Amp can made from two op amp
2) Can you use ADC module directory, It has the differential mode (however current module can't change the gain)
Or add op amps to this ADC
How about these?
The SAR ADC has differential mode, however its input buffer has only a gain of 1, gain
control as in PSOC 3/5 is not supported.
If you need more gain, then athe only way to get it would be external IA or external OpAmps
with precision R network to set gain, and its precision (and OpAmp G) control CMRR.
Some reference material attached.
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I have a lot more ref material, if you send me email address I can supply.
Thank you for your reply. And your means that the PSOC4 cannot do the application of thermal couple one chip solution?
And I have tried to change the sampling mode from differenctial mode to single mode with AMUX. But the common mode interfering noise is too big and the sample data is not good.
And the customer is interesting our one chip solution because of the low BOM cost and simple circuit. Maybe the application is not the target filed for PSOC4.
With respect to your CM noise you are experiencing -
1) If power supply related noise take a carefull look at grounding.
2) Use Polymer Tantalums vs standard tants, they have an order of magnitude
better Z vs f performance.
2) Band limit where possible, R-C filters, IIR and FIR filters in code.
Some additional info -
I have tried added a 358(two channel op) for PSOC4 application. But I found the analog bus cannot be routed internal in creator.Can you release your email address to me. And I will send the project configuration to you and help me to route it.
Ben, its -
I have sent a email to you. And I attached my project to you. Please help me to route it. Now it seems that there is a conflict when using AMUX and IDAC.
You have 2 OpAmps external, any thought to using 4200 part ?
Right now those OpAmp R networks have to be .1% to keep
common mode in spec (actually you would need to do a more
thorough analysis), and coupled with the cost of the 2 OAs might
offset cost of using 4200. Also 4200 enables the SAR input buffer
which allows G up to 16.
Just a thought.
Still looking at routing, seems like you are meeting all restrictions
and comitted poin issues, not obvious.
Question, when you choose ch2 (of ch0 - ch4) you essentially short the
SAR diff inputs together, is that what you intended ?