Question 1

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

Accepted Answer

Q 
 I can not find the full scale value for the velocity output in the AD2S1200 datasheet. 
 
 A 
 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 2

AD2S1200: interpreting the output velocity information

Accepted Answer

Q 
 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? 
 
 A 
 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 3

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

Accepted Answer

Q 
 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? 
 
 A 
 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 4

AD2S1200: What is full scale of velocity output and it is programmable or fixed?

Accepted Answer

Q 
 What's the velocity corresponding to full scale of digital velocity signal? Is it fixed or programmmable? 
 
 A 
 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. It is fixed i.e. not programmable.

Question 5

What is a power consumption of AD2S1200?

Accepted Answer

Q 
 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. 
 
 A 
 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 6

We are having some problems in the field with errors detected by the AD2S1200.

Accepted Answer

Q 
 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? 
 
 A 
 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: &bull; When the internal error signal of the AD2S1200 has exceeded 5&deg; &bull; When the input signal exceeds the maximum tracking rate of 60,000 rpm (1,000 rps) &bull; When the internal position (at the position integrator) differs from the external position (at the position register) by more than 5&deg; 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 7

Why AD2S1200 pin20 toggling with /RDVEL low and Resolver stationary?

Accepted Answer

Q 
 The signal bit (DB0) at pin 20 is toggling, when the /RDVEL is high (at the same time sample by the signal /RD), while the resolver is rotating, and stays at the last position when the resolver is stopped rotating. But the same pin 20 (DB0) is toggling randomly when /RDVEL is low (at the same time being sampled by the signal /RD), even when the resolver is stationary. 
 
 A 
 The AD2S1200's dynamic ripple specification is 1LSB typical and the overall velocity accuracy specification that includes the dynamic ripple is 2 LSB max. This means that a change in the LSB of the velocity output is highly possible in your application.

Question 8

Changing R11 and R17 for AD2S1200

Accepted Answer

Q 
 AD2S1200: Is there any problem with setting a lower value to R11 and R17? Is there a minimum value from the point of view of the AD2S1200? 
 
 A 
 The 10K resistors R11 and R17 have no impact on the AD2S1200 operation. You can set them lower if you wish. Just to be aware that these resistors will attenuate the input signals. The resistors should be tight tolerance, minimum 1% as the potential tolerance variation between the sine and cosine channels can lead to amplitude mismatch and therefore increased error.

Question 9

AD2S1200: SinCos Common Mode Input Voltage

Accepted Answer

Q 
 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? 
 
 A 
 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. 
 
 Attachments: 
 
 AD2S1200_SinCosCommonModeInputVoltage.docx

Question 10

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

Accepted Answer

Q 
 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. 
 
 A 
 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 11

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

Accepted Answer

Q 
 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. 
 
 A 
 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 12

AD2S12xx SIN/COS input CMV query

Accepted Answer

Q 
 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 &lsquo;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! 
 
 A 
 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. &ldquo;In this recommended configuration, the converter introduces a VREF/2 offset in the SIN, SINLO, COS, and COSLO signal outputs from the resolver.&rdquo; 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 13

AD2S1200: How are angular accuracy and resolution linked ?

Accepted Answer

Q 
 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? 
 
 A 
 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 &ndash;40degC to +85degC. Angular accuracy for AD2S1200 is specified as +/-11 or +/-22 arc min for Y or W grade device.

Question 14

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

Accepted Answer

Q 
 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? 
 
 A 
 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: Data bus high impedance mode control and max current load

Accepted Answer

Q 
 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? 
 
 A 
 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 16

AD2S1200: Connection methods

Accepted Answer

Q 
 In case of LOS, is pulling -RESET low for duration Ttrack enough or must the part, pulling reset low, be fully powered off then on? In brief is reset enough or do we need to cycle power? Should the resolver wires be disconnected from AD2S1200, which precaution should be taken to avoid damaging the part? Resistors across Sin/SinLo and Cos/CosLo? Pull-up or pull-down resistors? To which potential? 
 
 A 
 RESET should be fine, but must be held for at least 10uS after the power You must then wait 20ms before taking /SAMPLE low. There is no need to hold it for 20ms and there is no need to cycle power. On reviewing the input impedance (1Mohm), you don't need anything on the inputs. Pull-ups to 3.6V would be the only thing that you may need for safety.

Question 17

AD2S1200 or alternative for use with 2kHz excitation?

Accepted Answer

Q 
 The minimum excitation frequency of the AD2S1200 is 10kHz according to the data sheet. Is there a mode that the AD2S1200 can run with 2kHz excitation? Or is there an alternative part that can run at 2kHz? The resolver fitted to the motor is Tamagawa TS2640N1241E230 and 2kHz excitation. 
 
 A 
 It is not possible to set the excitation frequency to 2kHz. You can set the excitation frequency by pulling high or low the pins FS1 and FS2 as specified on pages 4 and on table 7 (page 16) of the datasheet. There is four possible frequencies 10, 12, 15 and 20kHz. You could use the AS2S1210, it has a programmable excitation frequency between 2 kHz and 20 kHz. However note AD2S1210 is not pin compatible with the AD2S1200.

Question 18

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

Accepted Answer

Q 
 Can I use split supplies of +3.3V for DVDD and +5V for AVDD on AD2S1200? 
 
 A 
 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 19

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

Accepted Answer

Q 
 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. 
 
 A 
 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&rsquo;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 20

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

Accepted Answer

Q 
 Can AD2S1200 be used with "SINCOS" sensor? 
 
 A 
 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 &plusmn;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&rdquo;

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AD2S1200: FAQ