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Changes for lower excitation voltage measurements

Question asked by gimbal on Jan 14, 2018
Latest reply on Jan 18, 2018 by mark.ramos

I would like to perform some 2-wire measurements on a sample that cannot see more than roughly 20mV. What changes would I need to make from the evaluation board to enable this?

 

From the hardware reference I see the following which I don't quite understand:

VAFE 8 = ((VDAC - 0.6 V) × 2) + VBIAS

 

Figure 91 in the reference makes me think I should be able to enable the attenuator to generate 30mVpp which should only be a swing of 15mV which my test sample should be okay with. However, would I need to adjust the VBIAS as well? For example, if the D node is at 1.115V and VBIAS is left at a default of 1.1V does the sample only see the delta (ie. 15mV)?

 

Also, I'm not quite clear on how all this would affect the receive stage. Do I need to adjust Rtia/Ctia to compensate for the lower voltage?

 

Finally, is there anything else I need to consider?

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