I'm working with LPC1796 and I have to do data acquisition for my project somebody told me that LPC1796 microcontroller won't work with resistive inputs.

What is a resistive input?

Is there any way to work with the same microcontroller on resistive inputs?

  • \$\begingroup\$ Did somebody also tell you that capital letters and punctuation are not required on this site? A link to the PROPER data sheet of the chip is probably also going to help you get an answer. \$\endgroup\$ – Andy aka Oct 15 '14 at 10:26
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    \$\begingroup\$ Huh? What's a "resistive input"? No, I'm not going to chase down a datasheet you should have provided a link for. The annoying writing puts it over the top. -1 and voting to close this mess. \$\endgroup\$ – Olin Lathrop Oct 15 '14 at 12:16

A "resistive input" is obviously an input with a relatively high impedance, such as a voltage divider. The risk is that the ADC input may load this, and alter the intended voltage - and it may do so in a manner that is not constant over time, but rather pulse-like.

Many microcontroller ADC inputs have an effective input impedance which is actually a function of the software-configured sample and/or clock rate. Other factors such as internal gain may also play a role. Generally, the faster you sample, the lower impedance the input is going to present (ie, the more it will load the driving circuit).

Some recent microcontrollers have an op-amp buffer stage you can enable in front of the ADC. If not, you can build your own op-amp voltage follower externally.

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