Position LSB (Arc min and Degrees) - AD2S1210

Question: How is Position LSB from Table 9 computed? Answer: Minute of an arc, or arc minute, is a unit of angular measurement. One arc minute is defined as one-sixtieth of a degree (1/60 degree). Table 9 refers to one complete rotation or 360 degrees. Computing the arc minute in Table 9: 360 / 2^N (where N is the resolution) If 10 bits will be used, Arc min is: 360 / (2^10) = 0.3516 degrees Converting to Arc min: 0.315 degrees x [60 min / 1 degree] = 21.1 min

Velocity LSB computation - AD2S1210

QUESTION: I noticed that Table 9 in the datasheet of ad2s1210 described the resolution. It mentioned that when in 12bit, the velocity LSB is 0.488rps. It seems that this value is also associated with CLKIN. I want to know that if the full scale of velocity is 500rps, LSB = 500/(2^11-1)=0.061rps. How to calculate velocity LSB in different full scales? Does it need to consider CLKIN value? ANSWER: Take note that the values of RPS also depend on the CLKIN . The computations below were referred to 8.192 MHz CLKIN. If CLKIN is changed to a different value, let's say 10.124 MHz, the maximum tracking rate will also change. The new max tracking rate is +/- 3125 rps. If the max tracking rate is a concern, then CLKIN should be considered. Calculating the Velocity LSB (rps): RPS_FS/ (2^n). For example, if your resolution (N) is 10 bits, you will have an RPS of +/- 2500 rps. For its full scale, you will be having 5000 rps. Solving for its Velocity LSB (rps): 5000 / (2^10) = 4.88 rps On the other hand, if your resolution is 16-bits. You will have an RPS of +/- 125 rps. Its full scale will be 250 rps. Solving for its Velocity LSB (rps): 250 / (2^16) = 0.004 rps So, if your FS is 500, then computation will be 500/(2^N).

AD2S1210: EXC/EXC- waveform incorrect issue

Q EXC/EXC- waveforms are correct when resolver is disconnected, but have some distortion once we connect the resolver. What do think could be the cause of this distorsion? A From your schematic, I can see that the issue is caused by the wrong connection of NPN transistor BC856. The emitter should be connected to 4.7ohm and collector should be connected to gnd. Please refer to AD2S1210 evaluation board schematic at: https://www.analog.com/media/en/technical-documentation/evaluation-documentation/ EVAL-AD2S1210.pdf Attachments: ez.analog.com/.../AD1210EXCEXC_2D00_waveformincorrectissue.rar

data sheet error. Hold time of A0 and A1 signal during SPI transfert on AD2S1210

Q T33, The hold time for A0, A1 do not seem to be correct or aligned to the parameters. A It should be related to SPI clock and not the CLKIN frequency. A0 and A1 should hold their value for the duration of the data read and after that they can be released or set to a new state. Upon review and analysis wrt AD2S1210 datasheet. There appears to have typo errors in the timing parameters. Have liaison with the author for this datasheet. The hold time for A0, A1 should be related to SPI clock and not the CLKIN frequency. Currently the datasheet is being revise to include these changes. Please see attached temporary cut down version for the time being.

Direct interface for resolver with AD2S1210

Q My task is to design an interface for a resolver. My problem is that the information in the datasheet does not clearly defines this. See AD2S1210-EP table 1 for the sine,cosine inputs. There is an amplitude required of 2.3 till 4 Vpp. In case of a direct connection of the resolver windings (see datasheet AD2S1210 page 19) and the electrical resolver representation on page 15, there are voltages possible of approx. 0Vpp.(for example sine 0°, cosine 90°). Could I use the RDC in this configuration or is a special signal conditioning necessary? Another question to the accuracy: my requirement to the static accuracy shall be less than +/-0,008rad. Is this possible? A There is no special circuitry required to interface between a resolver and the AD2S1210. The AD2S1210 is designed to be directly connectable to a resolver. Another way to read the specification would be that the maximum input signal amplitude should be within the 2.3 V to 4.0V range. At 0'degrees sine is 0 V, this is ok as long as when sine is at its maximum, @90'Degrees, that the peak to peak amplitude is within the 2.3V to 4.0V range. Accuracy of +/-0.008rad is +/-27.5 arc minutes. The AD2S1210-EP data sheet list a worst case accuracy of +/-7 + 1LSB arc minutes. For the respective resolutions this equates to the following : see table.gif (attached). The requirement of +/-0.008 rad is achieved for the AD2S1210-EP at 12-bit and greater resolution. Attachments:

Is it it is possible to use the AD2S1210EVB without the CED1Z ?

Q I want to know if it is possible to use the AD2S1210 EVB without the CED1Z board, interfacing it with a computer with serial or parallel connectors (J20 and J4)? If so, how can I connect the evaluation board to my computer (what kind of interface to make), and can I use the software provided with it to control it? A EVAL-CED1Z is the hardware interface method that ADI provides for AD2S1210 and the related software on the EVAL-AD2S1210EDZ CD is the interface/GUI software for controlling and evaluating the performance of the AD2S1210 when it is operated with the EVAL-CED1Z. The serial and parallell connectors J20 and J4 allow for access to AD2S1210 interface signals when interfacing to systems other than the EVAL-CED1Z. For connecting directly to PC you should use EVAL-CED1Z and the software provided on EVAL-AD2S1210EDZ CD.

Q Do I need a separate 96 way connector cable to connect the EVAL-AD2S1210 board to CED1Z board? And if yes, is it included in the CED1Z evaluation kit? A No cable is required. The EVAL-AD2S1210 board connector mates directly to the CED board connector.

AD2S1210: Resolver to Digital simulation models

Q Can you provide a Pspice model for simulation of any of the resolver parts? A We have no SPICE models for any of our any of our Resolver to Digital parts. You will find an IBIS model for AD2S1210 on the AD2S120 product page on our website. This is the only simulation model that we offer for these devices.

AD2S1210: Input connection filtering and shielding

Q My AD2S1210 customer always get Sin/Cos inputs clipping error even after lowering the gain of the EXC's buffer circuit. He also sees noise on Sin/Cos input and he would like to add a differential amplifier before the Sin/Cos input to reduce the noise. Also the SINLO and COSLO will be connected to GND. Is it workable for such a solution on noise issues? A Most of our customers doesn’t use active components between Resolver outputs and RDC inputs. Noise is typically reduced by simple RC filter with cut of frequency set around 500 kHz or even lower. You are allowed to operate the AD2S1210 in single ended mode however you cannot connect SinLO and CosLO terminals to GND as you definitely get clipping on the inputs. I advice to pull up SinLO and CosLO to 2.5 V instead of GND so that the clipping issue should not occur(i.e. through 10 kOhm resistors). To investigate the noise issue, ask your customer to send us the scope plots of Sin, SinLO, Cos, CosLO, Exc and /Exc signals ? If possible please also plot Sine and Cosine inputs differentially, all plots should be gathered at 0 and 90 degrees.

AD2S1210 interfaced to an LVDT

Q Is it possible to use the AD12S1210 as an interface for LVDTs? A You can use the AD2S1210 to interface with an LVDT, but some extra design is required in mapping the output from the AD2S1210 to an expected LVDT output.

AD2S1210 synchronized to external excitation

Q Can the AD2S1210 be operated with an externally generated sine wave reference? A It is tricky to synchronize the AD2S1210 to an external excitation. To achieve it you must ensure that the AD2S1210 and the device determining the excitation frequency have the exact same excitation frequency, are within the phase specification of +/-44 degrees, and do not phase drift outside of this specification over time.The AD2S1210 expects the sine and cosine signals to have the carrier at the settings that are defined in the AD2S1210 even though the system is not using the excitation of the AD2S1210. You must control the AD2S1210 with the same clock source as the creator of the system excitation frequency, the AD2S1210 must have the same frequency setting as the external excitation and you can control the synchronization of the excitation frequency with a hardware or software reset to the AD2S1210. The choice of software or hardware reset depends on if you wish to use a configuration in the AD2S1210 other than the default settings.

Q On my AD2S1210-EP board the measurement at the outputs EXC and NEXC shows a distorted signal of the sinewave. The output sine wave is overlayed with a distortion voltage (2.5MHz and 400mV). The supply voltage is filtered according to datasheet: see "filter.png" The output is buffered for EXC and NEXC (similar) as shown in the picture below. The output of the OP's goes to an excitation circuit. ("output_buffer.png") CLKIN is 10MHz. Please let me know if a similar behaviour is known and where the problem could be. A The 'noise' that you are seeing is normal. It is coming from the DDS which is generating the excitation outputs. Because the noise is on the excitation frequency and is therefore common to both the Sine and Cosine inputs it is taken out by the operation of the tracking loop. In addition the resolver itself acts as a natural filter. This means that the 'noise' which you are seeing will have no impact on the performance of the AD2S1210 in a resolver application. If you are concerned with the appearance of the noise I would suggest a filter stage in the excitation buffer. This is done on the AD2S1210 with a capacitor in parallel with the feedback resistor on our buffer circuit. Attachments: ResolverIssue.pdf

Is it possible to operate two AD2S1210 converters with one resolver?

Q Is it possible to operate two AD2S1210 converters with one resolver? A It is possible to operate two AD2S1210 converters with one resolver however proper synchronisation procedure must be followed. 1. Both devices must be clocked with the same signal from the same clock source (CLKIN input) 2. After initial configuration of the AD2S1210s the Software Reset command should be issued to both devices simultaneously. If this recommendation is met both devices are synchronized hence operation with one sensor is allowed. In case of using two RDC chips which are not successfully synchronized user may experience faults and incorrect output data from one device.