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AD598 excitation voltage output buffer and signal out range

Question asked by LarsGerd on Jul 5, 2017
Latest reply on Jul 30, 2017 by jcolao

Hi guys, I would love to understand the different voltage level behavior when the AD598 is powered by: 


a) an unipolar voltage, let´s say 25 Volt

b) a bipolar +-15V voltage


In respect to the excitation voltage outputs EXE1 and EXE2 and in respect to the SIG OUT + SIG REF pins.



When powered by a unipolar voltage, as of my understanding, also the output levels are unipolar. I don´t think the

device has an internal charge pump to generate a negative voltage.


Does the output buffer of the excitation buffer generate a pseudo-difference voltage swing on both pins with an offset for the 0 point or does it simply use EXC1 as signal output (max. 22,5 Vpp) and EXC2 remains its reference GND?


Can I connect the EXC2 to GND? In one of my application I need to interface with a RVDT who has its primary and secondary coils at one common reference (mid-point) connected together.


In case of an unipolar power supply, do you confirm that the SIG OUT is also unipolar? And which levels or swing are so

expect if the SIG REF is not connected to GND? Are here also pseudo-differential levels to expect.


An illustration or diagram of the respective output buffers would be useful.



When powered by a bipolar voltage (+-15V) in my understanding, its output levels are also bi-polar (differential) and

follow as in an differential buffer design. 


Thanks in advance for helping me to better understand the AD598 behavior in case of different power supply applications. Also if any other kind of documentation, integration or hardware design guide is available, it would

be much appreciated.