Anthony, The common mode range is the range of common mode voltages for which the CMRR specification is valid. If you are overdriveing the comparators differential input, this parameter is less important. For example, if the common mode input range is +/- 10V and the CMRR is
80dB, then a 10V common mode input can cause the input threshold to vary by 0.1 mV. If you are trying to detect a 1 mV differential in the presence of 10V Common mode, this may be significant. Regards,, JonLM393 Input Common Mode Voltage Range question
Mar 20, 2006
22 Replies
[snip]
Re-stating John Field's statement...
ONE INPUT must NEVER exceed VCM, otherwise the output is unpredictable.
Like wise there are restrictions below ground, but more complex... with 339/393 architectures the behavior depends on WHICH input goes below ground ;-)
...Jim Thompson
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
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It\'s what you learn, after you know it all, that counts.
No, what I said was that at least one input must be below VCM for
the output to be predictable.
That is, if one input is below VCM and the other is above VCM, the
output will be as predictable as if both inputs are below VCM.
The ground restrictions apply as well, of course.
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