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Questions on AD2S99/AD2S82A

Question asked by KevL on Jun 3, 2011
Latest reply on Jun 7, 2011 by ShaneO

Dear Sir/Mdm,


I currently have a project on Resolver-to-Digital conversion, and the R/D IC chip I'm using is AD2S82A. To make the R/D circuit works, first I need a sine wave excitation source feeding into resolver, and for this, I selected AD2S99 because in its manual, there is a typical circuit for AD2S99/AD2S82A (on page 6 of AD2S99 manual which you can find from I copied the circuit exactly and selected a frequency of exactly 5kHz using pin SEL1 and SEL2. Without damaging AD2S82A, I decided to test on the sine wave produced at pin 17 or 18 (EXC or EXC complement) with respect to GND first, using an oscilloscope, therefore I separated all the connections between AD2S99 and AS2S82A, and I only powered AD2S99 by providing it a dual supply +5V (at pin 12) and -5V (at pin 2 because my reference frequency at reference coil of resolver is to be 5kHz). The virtual ground (VGND) of the dual supply is connected to GND of the AD2S99 circuit, the black wire of oscilloscope is connected to the GND, and the another wire (red in my case) is connected to EXC, all connections on breadboard has been checked very carefully and for many times and the +5V and -5V generated by my dual power supply is double checked using multimeter as well as oscilloscope, all capacitors and resistors and wires are checked to make sure that they are working. According to page 2, the voltage between EXC and GND should be 2V rms (or Vp-p = 2 x root 2), but the value shown on oscilloscope is a DC voltage of 3V (voltage between EXC complement and GND is -3V, between EXC and EXC complement is slightly more than 6VDC). I checked on different frequencies, be it 2kHz, 10kHz and 20kHz, but all produced the same results. There is no connection at SIN and COS pin of AD2S99, according to the functional block diagram at page 1, the phase detect logic circuit is not a feedback to sine wave generator so I guess there is no need SIN and COS output from resolver to SIN and COS pin to make the sine wave generator works, and also since the resolver is shorted (merged) to an expensive robot, so there is a need for me to test the output at pin EXC/GND and EXC complement/GND and EXC/EXC complement first without implementing the whole AD2S99/AD2S82A connection. So by forgetting the phase detect logic circuit, after selecting a frequency of 5kHz, there should be output at EXC/GND and EXC complement/GND of 2V rms. Could it be AD2S99 originally faulty or due to ESD (electrostatic discharge) issue? Please advise me on my problem. Thousands thanks !


I asked experts around and at the moment, nobody are able to solve the problem.


Note: The AD2S99 is mounted on a 20 pins PLCC-to-DIP adapter for breadboard testing (prototyping) purpose.


For backup purpose, can you introduce me other types of sine wave generator IC chip to be used with AD2S82A? (Little price variation compared to AD2S99 is acceptable.)

Assuming if the problem is solved and I managed to observe a 2V rms at EXC/GND, what should be the voltage (either rms or p-p) for EXC/EXC complement? Why the resolver is connected across EXC and EXC complement but not EXC and GND?


If I don't wish to use the phase detect logic circuit, what should be fed into pin 1 (reference I/P) of AD2S82A, and for this case, is AC coupling (R3 and C3) necessary?


I am not sure about why the output of SYNREF is a square wave but not sine wave? It should be a sine wave according to figure 9, pg 14 of AD2S82A manual. I know that the phase detect logic bears a function of able to detect lossing of SIN and COS signal but what is the function of SYNREF of square wave (and I thought it should be a sine wave)?


Thank you ! Your reply will be greatly appreciated !