Question 1

AD2S1200 velocity output resolution

Accepted Answer

Question If the motor is running under a slow speed for example 0.5 rps, is the 0.488rps 
 LSB a little bit small? Is there any way to improve it? Answer If the customer is using the velocity output as feedback to drive them motor 
 and If that motor is always running at a slow speed, e.g. 0.5rps then the 
 AD2S1200 is not the correct part for this application. The LSB size is too 
 big and will cause difficulties. 
 However, most customers actually use the position output to commutate the 
 motor, not the velocity output. The LSB of the position output is 5.3 arc mins 
 i.e.0.09 degrees. 
 If your customer is concerned they should consider the AD2S1210, which offers 
 16 bit resolution on the velocity output across a full-scale range of +/-125rps 
 i.e. LSB size of 0.004rps.

Question 2

AD2S1200: The full scale value for the velocity output is not given in datasheet

Accepted Answer

Question I can not find the full scale value for the velocity output in the AD2S1200 
 datasheet. Answer The velocity output of the AD2S1200 is in twos complement format and is scaled 
 to a maximum velocity of +/-1,000rps [60,000rpm] i.e. when reading back 
 velocity 800h will represent -1,000rps and 7FFh will represent +1,000rps. Each 
 bit is equivalent to 1000rps / 2048 i.e. 0.488rps.

Question 3

AD2S1200: Data bus high impedance mode control and max current load

Accepted Answer

Question Is the high impedance mode of the data bus lines just controlled by the 
 RD-Signal or also by the CS-Signal?
 What is the max. current load of data bus signals? Answer The output buffer is enabled when CS and RD are held low, both RD-Signal and 
 CS-Signal are needed for high impedance control.
 
 The datasheet specifies 2mA/-1mA load conditions for data bus electrical 
 specifications (page 5 of datasheet).

Question 4

AD2S1200: How are angular accuracy and resolution linked ?

Accepted Answer

Question How are angular accuracy and resolution linked and why does a 12 bit resolver 
 to digital have 10.6 arcmin instead of 5.3 arcmin? Answer There are 21600 (360*60) arc min in 1 revolution. In 12 bit system there are 
 4096 codes. I LSB = 21600/4096 = 5.3 arc min. 
 The angular accuracy of AD2S90 is specified to be a min +/-10.6 arc min +1LSB 
 for an ambient temperature range that spans –40degC to +85degC. Angular 
 accuracy for AD2S1200 is specified as +/-11 or +/-22 arc min for Y or W grade 
 device.

Question 5

AD2S1200: interpreting the output velocity information

Accepted Answer

Question When accessing the velocity information. ie /RDVEL pin is low. What are the 
 units that the velocity is measured in? And what are the limits that the device 
 can read? Answer The digital velocity output of the AD2S1200 represents the velocity of the 
 resolver shaft rotating in either a clockwise or anti-clockwise direction. The 
 digital output is in twos complement format and is scaled to a maximum velocity 
 of +/-1,000rps [60,000rpm] i.e. when reading back velocity 800h will represent 
 -1,000rps and 7FFh will represent +1,000rps. Each bit is equivalent to 1000rps 
 / 2048 i.e. 0.488rps.

Question 6

AD2S1200: EXC Driving Circuit

Accepted Answer

Question The position data of the resolver, AD2S1200, sometimes has a 180 degree error. For example, if the angle is 10 degree, sometimes, it reads out 10degree, but sometimes, it reads out 190 degree. The input was tested, it is 3.6Vp-p and the DOS and LOT are high level.Below is the further information on the issue.1. When the angle is 0 degree, the sin sinlo amplitude is 0V. The cos and coslo amplitude is 3.6V.When the angle is 90 degree, the sin sinlo amplitude is 3.6V. The cos and coslo amplitude is 0V.I am still asking the scope from the customer. After he sends it to me, I will forward to you.2 The part was reset, however, it can not fix the error.3. Pin 36 and pin 42 are connected to GND. The resolver_R1 and resolver_R2 are the inputs to resolver EXC and /EXC.4. The resolver is stationary at 10 degree position. If the part is powered on and the output is correct (10 degree), it will be always correct. Ifthe part is powered on and the output is wrong, the output will always be wrong(190 degree) unless they power down and power up the part again.EXC/EXC waveforms have some spikes. It seems the driving circuitry has some problems. What amplifier and transistor part numbers do ADI recommend inthe buffer circuit? Answer Please find attached buffer circuit which is recommended by ADI and used on our evaluation boards. Resistor values may vary however we use thisbuffer topology. Our proposal doesn’t provide extra protection for example for ESD, overvoltage, short to supplies etc. situations. Very oftencustomers modify this circuit to fit into their application. Could you ask your customer to use our proposal and check if the 180 degree issue still exists ?The transistors used in our evaluation board are:BC846BBC856BLT1AD8662 is our proposal for the operational amplifier.

Question 7

AD2S1200_Velocity Output Calculation

Accepted Answer

Question For AD2S1200, the Position is easy to understand which is Output*360 degree/1024. but for velocity output ,how to calculate the absolute velocity. Ican not find the formula in datasheet. for example, if I read the 11 bits velocity output which is 200, and the system clock is 4.096M,what's theabsolute velocity? Could you give any suggestion on this? Answer The full-scale velocity output is equal to the max tracking rate of the part. For the AD2S1200, with an 8.192MHz clock, the max tracking rate is+/-1,000rps i.e. clockwise/anticlockwise rotation. This makes each LSB equal to 0.488rps [11 bits in 1,000rps or 12 bits in +/-1,000rps].If your customer is using a different clock frequency then they need to scale the max tracking rate and LSB size with the clock. For examples,increasing the clock by 10% increases the max trackingrate and the LSB size by 10% also. Feedback: NO

Question 8

What is a power consumption of AD2S1200?

Accepted Answer

Question In data Sheet it states only: "POWER SUPPLY IDD Dynamic 18 mA", but for the 
 power budget I need to know the worst case. Can you provide separate values for 
 AVDD and DVDD (both 5V). The Load on EXC/bEXC is around 5k 
 each. Answer IDVDD and IAVDD are both max at 10 mA. The EXC load shouldn't really matter as 
 the EXC output cannot be used to drive resolver directly therefore buffer 
 circuitry is needed.

Question 9

AD2S1200: Can AD2S1200 be used with "SINCOS" sensor?

Accepted Answer

Question Can AD2S1200 be used with "SINCOS" sensor? Answer Yes, if by "SINCOS" sensor you mean a Resolver (resolver is like a 
 motor/generator with windings at 90 degrees so it gives Sin/Cos outputs). 
 The converter accepts 3.6Vp-p ±10% input signals, centered around 2.5V, in the 
 range 10 kHz 20 kHz on the Sin and Cos inputs. A Type II servo loop is employed 
 to track the inputs and convert the input Sin and Cos information into a 
 digital representation of the input angle and velocity”

Question 10

AD2S1200: Angular position data format vs, Angular velocity data format

Accepted Answer

Question There appears to be different data formats for the angular position data 
 compared to the angular velocity data? Answer For the AD2S1200, the angular position data format is unsigned binary, with all 
 zeros corresponding to 0 degrees and all ones corresponding to 360 degrees –l 
 LSB. The angular velocity data format instead is twos complement binary, with 
 the MSB representing the rotation direction.

Question 11

AD2S1200: Maximun phase shift that can be tolerated between the reference excitation and the sin/cos signals?

Accepted Answer

Question We want to have an error due to Phase shift of less then 1 lsb with these 
 parameters: RotationRate=6000rpm ReferenceFrequency=10Khz. What is the maximun 
 phase shift that can be tolerated between the reference excitation and the 
 sin/cos signals. Answer The Error you are referring to is caused by the rotation of the resolver. 
 Basically at high rotation rates the resolver starts to act like an electric 
 motor and produces speed voltages. This are in quadrature to the main signal 
 and result in an additional error through the RDC. 
 
 The formula to calculate this error is on page 17 of the datasheet:
 Error = Phase shift x [rotation rate / reference frequency]
 
 The main factor in the formula is the Phase shift, which is the phase shift 
 between the reference signal and the Sin/Cos inputs. This phase shift is 
 primarily caused by the resolver itself i.e. resistance of the rotor coil 
 causes a phase shift from what is applied to the rotor to what is then 
 generated across the stators. 
 
 The AD2S1200 internally generates a synthetic reference to compensate for this 
 phase shift. It can reduce a phase shift of +/-45 degrees down to 10 degrees. 
 
 However for you this is not quite enough as he would then have the following
 with the speed and freq conditions he outlined :
 Error = 10 degrees x [100rps / 10kHz]
 = 0.1 degrees = 6 arc min
 One lsb = 5.3 arc min. 
 
 The reduce this error still further you need to further reduce the phase shift 
 between the
 reference and the Sin/Cos signals. So after all that explanation the answer to 
 your 
 questions is:
 
 Error = Phase shift x [rotation rate / reference frequency]
 => Phase shift = Error x [reference freq / rotation rate]
 = [0.088 degrees] x [10,000/100]
 = 8.83 degrees. 
 
 i.e. You need to keep the phase shift below 8.8 degrees to be able to keep the 
 additional error below 1 lsb [5.3 arc min.]

Question 12

AD2S1200: SinCos Common Mode Input Voltage

Accepted Answer

Question I have a question about AD2S1200 sin/cos input. The datasheet says that, 
 voltage swing is 3.6Vpp typically, but the common mode volts is 100mV, respect 
 to Refout. Does it mean the common mode voltage should be Refout+/-0.1V?
 
 But I also find another description in datasheet where it says the converter 
 introduce a Vref/2 offset in the sin/cos signal.
 So I am confused that whether the offset should be Vref/2 or Vref, and is that 
 offset generated by AD2S1200 internally or we need to introduce a offset 
 externally in the input signal.
 
 Also, if I find the sin/cos signal(Vpp) from resolver is smaller than the 
 requirement of 3.6Vpp, what should I do to amplify the input signal. May I 
 could try to use a large Exc signal by changing the gain of buffer circuit? 
 Answer The Common mode Volts spec should be with respect to Refout/2. The AD2S1200 
 internally generates the bias that will centre the input differential signals 
 on refout/2. The customer can overdrive this is desired, in which case they 
 should ensure that the inputs are at all times between 0.2V and Vdd [see Note 
 1.]
 If the inputs are too small the best option is to increase the gain on the 
 excitation buffer amp. This is the simplest and should introduce no additional 
 error. Another option is to introduce gain on both the Sine and Cosine 
 differential signals. However this is twice the effort and can introduce 
 amplitude mismatch between the Sine and Cosine if proper care is not taken.

Question 13

AD2S1200: Can I use both the serial and the parallel mode for velocity and position information?

Accepted Answer

Question Can I use both the serial and the parallel mode for velocity and position 
 information respectively?
 (By switching respective signal inputs) There are not many 2s complement DACs 
 available in parallel mode,
 so I could select the R/D to give velocity information in serial mode and 
 position 
 information in parallel mode, I need to use the parallel mode for position 
 information. Answer Typically customer application will use either serial or parallel interfaces to 
 read velocity and position but you can use both parallel and series interfaces. 
 The 2’s complement velocity output can be read on the serial port and you can 
 use the parallel port to read the position data (straight binary). Use /SOE to 
 select between serial and parallel interface and /RDVEL to select between 
 angular position and velocity registers.

Question 14

AD2S1200: Does the angular accuracy figure take into account missing codes?

Accepted Answer

Question In the accuracy specification, does the 'missing codes' figure just refer to 
 cases where the least significant bit doesn't change between angles which 
 differ by 1 lsb.?
 Does the angular accuracy figure take into account missing codes? Answer The missing code spec for AD2S80A only applies to 16 bit resolution, it can be 
 up to 4 codes across the full range for particular grades. Your definition is 
 correct i.e. if a missing code occurs the LSB will not change even though the 
 angle has changed. The angular accuracy spec does take into account the missing 
 codes spec.

Question 15

AD2S1200 LOS, DOS and LOT Detection Errors limits?

Accepted Answer

Question We are having some problems in the field with errors detected by the AD2S1200. 
 In some instances we are getting lower excitation voltage than we expected 
 (3.35V pk-pk compared to 3.6V pk-pk). Although this is within device 
 specification, I would like to know:
 1. Does the Loss of Signal feedback level for low and high received signals 
 track the excitation output? In other words, if the excitation amplitude is at 
 the bottom end of the range (3.34V), is the Loss of Signal threshold also at 
 the bottom end of its range (2.9V)? Or could the Loss of Signal threshold be 
 higher? 
 2. What is the maximum value for the minimum signal amplitude before a fault 
 (LOS or LOT) occurs? Is it 3.0V?
 3. What failure mechanisms operate when the received signals (Sin/Cos) have 
 higher amplitude than expected? Is it always LOS and is the level always 3.96V 
 pk-pk? What is the range of values for the high signal amplitude fault?
 4. Is it possible to determine from the serial output word whether the fault 
 was high amplitude signal or low amplitude signal?
 Answer Please see comments to your questions below.
 
 1. Does the Loss of Signal feedback level for low and high received signals 
 track the excitation output? In other words, if the excitation amplitude is at 
 the bottom end of the range (3.34V), is the Loss of Signal threshold also at 
 the bottom end of its range (2.9V)? Or could the Loss of Signal threshold be 
 higher? 
 PL: The LOS threshold is fixed, internal registers do not update. The typical 
 value is 2.92 volts. The variation in the threshold is due to the variation in 
 the reference voltage. The reference voltage variation also leads to a change 
 in the excitation amplitude.

2. What is the maximum value for the minimum signal amplitude before a fault 
 (LOS or LOT) occurs? Is it 3.0V?
 PL: 
 LOT does not depend on the amplitude, Loss of tracking (LOT) is detected for 
 three separate conditions:
 • When the internal error signal of the AD2S1200 has exceeded 5°
 • When the input signal exceeds the maximum tracking rate of 60,000 rpm (1,000 
 rps)
 • When the internal position (at the position integrator) differs from the 
 external position (at the position register) by more than 5°
 
 The LOS is default and typically 2.92V. The range is 2.86 min to 3.0 volt max. 
 The variation is due to part to part variation, reference part to part 
 variation and reference drift.

3. What failure mechanisms operate when the received signals (Sin/Cos) have 
 higher amplitude than expected? Is it always LOS and is the level always 3.96V 
 pk-pk? What is the range of values for the high signal amplitude fault?
 PL: : The DOS is detected is either resolver input exceed the specified DOS 
 Sin/Cos thresholdby comparing the monitor signal to a fixed maximum value. 
 Again the DOS is linked to the reference. The typical value is 4.09V. The range 
 is 4.0 volt to 4.2 volts.

4. Is it possible to determine from the serial output word whether the fault 
 was high amplitude signal or low amplitude signal?
 PL: The bits in the serial output match the function of the pins. A LOS will 
 indicate with both LOT and DOS low.
 DOS will indicate with DOS low and LOT high.
 LOT will indicate with LOT low and DOS high.
 The faults have a priority, LOS will take precedence over DOS so it should be 
 possible to detect the faults separately.
 
 To summarize in general the excitation amplitude will track the input range. 
 For parts with a higher than normal excitation amplitude these parts should 
 have a LOS and DOS at the upper limit. For parts with a lower than normal 
 excitation amplitude these parts should have a LOS and DOS at the lower limit.
 
 A 3.35Vp-p excitation voltage would be quite low though. Are the excitation 
 outputs being buffered? The excitation outputs can only supply a small load and 
 therefore should be buffered before going to the resolver.
 What about the reference voltage level. Is this within specification?

Question 16

AD2S1200: MSB to LSB order of Databits is different to other AD2S parts

Accepted Answer

Question In the datasheet for AD2S1200, it does not say which is the LSB and the MSB. In 
 the datasheet for AD2S82, DB16 is given as the LSB ans DB1 as the MSB (which 
 is an odd numbering, usually the lowest number is the LSB).Is it the same for 
 AD2S1200 that DB0 is MSB and DB11 is LSB, or the other way around? Answer It is the other way around for the AD2S1200, the MSB is DB11, LSB is DB0. For 
 the other AD2S devices you refer to, the lowest number is the MSB. We recognise 
 that this is confusing and we hope to add some clarification to future 
 revisions of AD2S1200 datasheet.

Question 17

AD2S12xx SIN/COS input CMV query

Accepted Answer

Question I have a query about the Comment Mode Voltage of SIN/COS input in our AD2S12XX 
 family, It seems not the same about this parameter ‘s comment among the 
 datasheet of AD2S1200/AD2S1205/AD2S1210. 
 for the AD2S1200, CMV description:Common Mode Volts 100 mV Peak CMV @ SinLO, 
 CosLO, with respect to REFOUT @ 10 kHz 
 For the AD2S1205, CMV description: Common-Mode Voltage
 100
 mV peak
 CMV with respect to REFOUT/2 at 10 kHz
 For the AD2S1210, there is no description about the CMV .
 
 as the SIN/COS input VP-P is 2.3V~4V with AD2S1200 and AD2S1205,and the 
 voltages Sin, SinLO, Cos, and CosLO relative to AGND must always be between 0.2 
 V and AVDD.so the CMV would be above the 4/2=2V, right? How to understand the 
 100 mVpeak. 
 Or we try to understand the CMV as the SIN pin or COS pin absolute input 
 value ,and the 100 mv is the offset value which respect to REFOUT , while, why 
 the respect value is REFOUT in AD2S1200 and is REFOUT/2 in AD2S1205?
 I was a little puzzle about it ,could you help to clarify ? thanks a lot!
 Answer The specification means that the part will set up a common mode on the inputs 
 signals with a resolver connected with no external circuitry between the 
 resolver and the AD2S1205 which will be within 100mV of the Refout/2 voltage
 The AD2S1200 spec should also say Refout/2.
 
 For the AD2S1210 the common mode would also be REFOUT/2. It was removed from 
 the spec table in the AD2S1210 but is referred to later on in the data sheet on 
 page 19.
 “In this recommended configuration, the converter introduces a VREF/2 offset in 
 the SIN, SINLO, COS, and COSLO signal outputs from the resolver.”
 
 For a max 4Vpk-pk differential signal this would be split 50:50 between Sin and 
 SinLo. That gives a 2V pk-pk signal per input. With a 1.25V common mode that 
 gives a range of 0.25V to 2.25V.

Question 18

AD2S1200: Which device grade is populated on the AD2S1200CB evaluation board?

Accepted Answer

Question I would want to know if AD2S1200CB evaluation board is populated with the 
 AD2S1200YST or AD2S1200WST. What is the accuracy of AD2S1200CB? There is no 
 mention in the evaluation board technical note of which device type is 
 populated. Answer The evaluation board comes with the Y grade 11 arc min accuracy device: 
 AD2S1200YST. This is not mentioned in the evaluation board technical note.

Question 19

AD2S1200: Can I use split supplies of +3.3V for DVDD and +5V for AVDD?

Accepted Answer

Question Can I use split supplies of +3.3V for DVDD and +5V for AVDD on AD2S1200? Answer The AD2S1200 cannot operate on split supplies of +3.3V for DVDD and +5V for 
 AVDD. The supply voltage range on the datasheet for both AVDD and DVDD is 
 5V+/-5%. If you want to run the databus at 3.3V you will need to reduce the 
 AD2S1200 logic high output voltage from c.5V down to 3.3V max. However, 3.3V 
 signals flowing in the opposite direction, from the bus to the AD2S1200 don't 
 need any level shifting since the Vinh min is 2V.

Question 20

AD2S1200_EXC attenuation and excitation frequency range

Accepted Answer

Question For AD2S1200, I have two questions:1. If the resolver need 10Vpp EXC voltage, we can amplify the EXC output of AD2S1200. But the resolver's output(SIN and COS Input) will be 5Vpp, 5Vppis out of the range of Sin,Cos INPUTs. If we attenuate the 5V signal down to 3.6V, whether it's OK? 2. If the resolver need 3kHz EXC frequency, whether we can use a external Divider to divide the 12 kHz frequency, then we can get a 3kHz frequency?Also for these questions, I think we can use AD2S1210, because AD2S1210's EXC frequency can be 2kHz~20kHz. Answer 1. There are two possible ways of dealing with this situation. First as you said is attenuation of the Sine and Cosine signals to match the AD2S1200datasheet specs but please bear in mind that 1 % tolerance components should be use – resistor divider. The second option would be to reduce theamplitude of the excitation signal to achieve correct amplitudes of Sine and cosine signals for the AD2S1200. Both solutions should be fine howeverit’s customer decision what way they want to go.2. No, you are not allowed to change the frequency of the excitation signal therefore the AD2S1200 isn’t the best part to use in this application. asyou said the AD2S1210 would be much better part for this application especially when resolver requires low frequency excitation signal – 3 kHz. Feedback: NO

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AD2S1200: FAQ