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CN-0359, RTD measurement, the use of AIN9/DACBUFF+

Question asked by KevinPhe on Aug 25, 2016
Latest reply on Sep 7, 2016 by R.L

Hello Everyone,

When measuring the Pt-RDT, CN-0359 (Section: RTD Measurement, Page 4) adds 115mV to AIN9/DACBUFF+, saying that this allows for buffered operation. (I assume reference buffers and not input buffers). But as far as I understand, the DAC is not being used in NPN mode, so the DACBUFF is unnecessary. The DAC is not being used for the RTD measurement at all, neither is AIN9 being used as an input. Isn't DACBUFF used differently anyway? (cf. UG-367, Section: DAC NPN Transistor Driver Mode, Page 52).

Should this offset instead not be connected to VREF-, thus allowing the use of the VREF buffers? The question remains, what is VREF+?

 

Further, in the circuit digram (EVAL-CN0359-EB1Z-PadsSchematic-RevA.pdf) both VREF- and VREF+ are grounded, which confuddles me more.

 

I'd be greatful if you could unconfuse me.

Thanks in advanvce,

K

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