AD AD2S80ALD Variable resolution, monolithic resolver-to-digital converter Datasheet

DEMOD
O/P
INTEGRATOR
I/P
AC ERROR
O/P
DEMOD
I/P
AD2S80A
SIN I/P
SIG GND
COS I/P
ANALOG
GND
RIPPLE
CLK
A1
A3
SEGMENT
SWITCHING
R-2R
DAC
A2
16-BIT UP/DOWN COUNTER
+12V
–12V
INTEGRATOR
O/P
PHASE
SENSITIVE
DETECTOR
VCO DATA
TRANSFER
LOGIC
VCO I/P
OUTPUT DATA LATCH
INHIBIT
DIR
16 DATA BITS
BYTE
SELECT
+5V
DIG GND
BUSY
DATA
LOAD
ENABLE
APPLICATIONS
DC Brushless and AC Motor Control
Process Control
Numerical Control of Machine Tools
Robotics
Axis Control
Military Servo Control
FUNCTIONAL BLOCK DIAGRAM
SC1
FEATURES
Monolithic (BiMOS ll) Tracking R/D Converter
40-Pin DIP Package
44-Pin LCC Package
10-,12-,14- and 16-Bit Resolution Set by User
Ratiometric Conversion
Low Power Consumption: 300 mW typ
Dynamic Performance Set by User
High Max Tracking Rate 1040 RPS (10 Bits)
Velocity Output
Industrial Temperature Range Versions
Military Temperature Range Versions
ESD Class 2 Protection (2,000 V min)
/883 B Parts Available
SC2
a
Variable Resolution, Monolithic
Resolver-to-Digital Converter
AD2S80A
PRODUCT HIGHLIGHTS
GENERAL DESCRIPTION
Monolithic. A one chip solution reduces the package size required and increases the reliability.
The AD2S80A is a monolithic 10-, 12-, 14- or 16-bit tracking
resolver-to-digital converter contained in a 40-pin DIP or 44pin LCC ceramic package. It is manufactured on a BiMOS II
process that combines the advantages of CMOS logic and bipolar high accuracy linear circuits on the same chip.
Resolution Set by User. Two control pins are used to select
the resolution of the AD2S80A to be 10, 12, 14 or 16 bits allowing the user to use the AD2S80A with the optimum resolution for each application.
The converter allows users to select their own resolution and dynamic performance with external components. This allows the users
great flexibility in defining the converter that best suits their system requirements. The converter allows users to select the resolution to he 10, 12, 14 or 16 bits and to track resolver signals
rotating at up to 1040 revs per second (62,400 rpm) when set to
10-bit resolution.
The AD2S80A converts resolver format input signals into a parallel natural binary digital word using a ratiometric tracking conversion method. This ensures high-noise immunity and tolerance
of lead length when the converter is remote from the resolver.
The 10-, 12-, 14- or 16-bit output word is in a three-state digital logic available in 2 bytes on the 16 output data lines. BYTE
SELECT, ENABLE and INHIBIT pins ensure easy data transfer to 8- and 16-bit data buses, and outputs are provided to allow for cycle or pitch counting in external counters.
An analog signal proportional to velocity is also available and
can be used to replace a tachogenerator.
The AD2S80A operates over 50 Hz to 20,000 Hz reference
frequency.
Ratiometric Tracking Conversion. Conversion technique
provides continuous output position data without conversion
delay and is insensitive to absolute signal levels. It also provides
good noise immunity and tolerance to harmonic distortion on
the reference and input signals.
Dynamic Performance Set by the User. By selecting external resistor and capacitor values the user can determine bandwidth, maximum tracking rate and velocity scaling of the
converter to match the system requirements. The external components required are all low cost preferred value resistors and
capacitors, and the component values are easy to select using
the simple instructions given.
Velocity Output. An analog signal proportional to velocity is
available and is linear to typically one percent. This can be used
in place of a velocity transducer in many applications to provide
loop stabilization in servo controls and velocity feedback data.
Low Power Consumption. Typically only 300 mW.
Military Product. The AD2S80A is available processed in accordance with MIL-STD-883B, Class B.
REV. A
MODELS AVAILABLE
Information on the models available is given in the section
“Ordering Information.”
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
AD2S80A–SPECIFICATIONS (typical at +258C unless otherwise noted)
Parameter
Conditions
Min
SIGNAL INPUTS
Frequency
Voltage Level
Input Bias Current
Input Impedance
Maximum Voltage
50
1.8
Bandwidth1
ACCURACY
Angular Accuracy
Monotonicity
Missing Codes (16-Bit Resolution)
VELOCITY SIGNAL
Linearity
Reversion Error
DC Zero Offset2
DC Zero Offset Tempco
Gain Scaling Accuracy
Output Voltage
Dynamic Ripple
Output Load
INPUT/OUTPUT PROTECTION
Analog Inputs
Analog Outputs
50
1.0
arc min
arc min
arc min
4
1
Codes
Code
63
±2
6
± 10
± 10.5
1.5
1.0
% FSD
% FSD
mV
µV/°C
% FSD
V
% rms O/P
kΩ
± 10.4
V
mA
3
LSTTL
600
ns
35
110
ns
60
140
ns
–22
Overvoltage Protection
Short Circuit O/P Protection
Logic LO Enables Position
Output. Logic HI Outputs in
High Impedance State
±8
±9
± 5.6
±8
±8
3
LOGIC LO
MS Byte DB1–DB8,
LS Byte DB9–DB16
LS Byte DB1–DB8,
LS Byte DB9–DB16
Time to Data Available
SHORT CYCLE INPUTS
SC1 SC2
0
0
0
1
1
0
1
1
68 +1 LSB
64 +1 LSB
62 +1 LSB
±1
±1
Logic LO to Inhibit
BYTE SELECT
Sense
LSB
Degrees
rps
rps
rps
rps
Over Full Range
INHIBIT3
Sense
Time to Stable Data
ENABLE Time
1
+10
1040
260
65
16.25
–10
A, J, S
B, K, T
L, U
Guaranteed Monotonic
A, B, J, K, S, T
L, U
1 mA Load
Mean Value
Hz
V rms
nA
MΩ
V pk
Hz
V pk
nA
MΩ
60
(Signals to Reference)
10 Bits
12 Bits
14 Bits
16 Bits
User Selectable
Units
20,000
8.0
150
1.0
10, 12, 14, and 16
Bidirectional Natural Binary
ENABLE
20,000
2.2
150
8
DIGITAL POSITION
Resolution
Output Format
Load
3
2.0
60
1.0
REFERENCE INPUT
Frequency
Voltage Level
Input Bias Current
Input Impedance
CONTROL DYNAMICS
Repeatability
Allowable Phase Shift
Tracking Rate
AD2S80A
Typ
Max
Internally Pulled High
(100 kΩ) to +VS
10 Bit
12 Bit
14 Bit
16 Bit
–2–
REV. A
AD2S80A
Parameter
Conditions
DATA LOAD
Sense
Min
Internally Pulled High (100 kΩ)
to +VS. Logic LO Allows
Data to be Loaded into the
Counters from the Data Lines
BUSY3
Sense
AD2S80A
Typ
Max
Units
150
300
ns
600
1
ns
LSTTL
3
LSTTL
3
LSTTL
Logic HI When Position O/P
Changing
Width
Load
200
Use Additional Pull-Up
DIRECTION3
Sense
Logic HI Counting Up
Logic LO Counting Down
Max Load
RIPPLE CLOCK
Sense
3
Width
Reset
Load
DIGITAL INPUTS
High Voltage, VIH
Low Voltage, VIL
DIGITAL INPUTS
High Current, IIH
Low Current, IIL
DIGITAL INPUTS
Low Voltage, VIL
Low Current, IIL
DIGITAL OUTPUTS
High Voltage, VOH
Low Voltage, VOL
THREE-STATE LEAKAGE
Current IL
Logic HI
All 1s to All 0s
All 0s to All 1s
Dependent on Input Velocity
Before Next Busy
INHIBIT, ENABLE
DB1–DB16, Byte Select
± VS = ± 10.8 V, VL = 5.0 V
INHIBIT, ENABLE
DB1–DB16, Byte Select
± VS = ± 13.2 V, VL = 5.0 V
300
2.0
0.8
V
INHIBIT, ENABLE
DB1–DB16
± VS = ± 13.2 V , VL = 5.5 V
INHIBIT, ENABLE
DB1–DB16, Byte Select
± VS = ± 13.2 V, VL = 5.5 V
± 100
µA
± 100
µA
ENABLE = HI
SC1, SC2, Data Load
± VS = ± 12.0 V, VL = 5.0 V
ENABLE = HI
SC1, SC2, Data Load
± VS = ± 12.0 V, VL = 5.0 V
1.0
V
–400
µA
DB1–DB16
RIPPLE CLK, DIR
± VS = ± 12.0 V, VL = 4.5 V
IOH = 100 µA
DB1–DB16
RIPPLE CLK, DIR
± VS = ± 12.0 V, VL = 5.5 V
IOL = 1.2 mA
2.4
DB1–DB16 Only
± VS = ± 12.0 V, VL = 5.5 V
VOL = 0 V
± VS = ± 12.0 V, VL = 5.5 V
VOH = 5.0 V
NOTES
1
Refer to small signal bandwidth.
2
Output offset dependent on value for R6.
3
Refer to timing diagram.
Specifications subject to change without notice.
All min and max specifications are guaranteed. Specifications in boldface are tested on all production units at final electrical test.
REV. A
V
–3–
V
0.4
V
± 100
µA
± 100
µA
AD2S80A–SPECIFICATIONS (typical at +25 C unless otherwise noted)
8
Parameter
RATIO MULTIPLIER
AC Error Output Scaling
PHASE SENSITIVE DETECTOR
Output Offset Voltage
Gain
In Phase
In Quadrature
Input Bias Current
Input Impedance
Input Voltage
INTEGRATOR
Open-Loop Gain
Dead Zone Current (Hysteresis)
Input Offset Voltage
Input Bias Current
Output Voltage Range
VCO
Maximum Rate
VCO Rate
VCO Power Supply Sensitivity
Increase
Decrease
Conditions
Min
10 Bit
12 Bit
14 Bit
16 Bit
w.r.t. REF
w.r.t. REF
–0.882
Units
177.6
44.4
11.1
2.775
mV/Bit
mV/Bit
mV/Bit
mV/Bit
–0.9
60
1
At 10 kHz
± VS = ± 10.8 V dc
±7
± VS = ± 12 V dc
Positive Direction
Negative Direction
7.1
7.1
+VS
–VS
+VS
–VS
mV
–0.918
± 0.02
150
V rms/V dc
V rms/V dc
nA
MΩ
V
63
100
1
60
5
150
7.9
7.9
1.1
8.7
8.7
+0.5
–8.0
–8.0
+2.0
1
70
–1.22
±8
+10.8
–10.8
+5
± VS @ ± 12 V
± VS @ 13.2 V
+VL @ ± 5.0 V
12
±8
57
Input Offset Voltage
Input Bias Current
Input Bias Current Tempco
Input Voltage Range
Linearity of Absolute Rate
Full Range
Over 0% to 50% of Full Range
Reversion Error
Sensitivity of Reversion Error
to Symmetry of Power Supplies
POWER SUPPLIES
Voltage Levels
+VS
–VS
+VL
Current
± IS
± IS
± IL
AD2S80A
Typ
Max
612
619
60.5
dB
nA/LSB
mV
nA
V
MHz
kHz/µA
kHz/µA
%/V
%/V
%/V
%/V
mV
nA
nA/°C
V
5
380
±8
<2
<1
1.5
% FSD
% FSD
% FSD
%/V of
Asymmetry
+13.2
–13.2
+13.2
V
V
V
623
630
61.5
mA
mA
mA
Specification subject to change without notice.
All min and max specifications are guaranteed. Specifications in boldface are tested on all production units at final electrical test.
ESD SENSITIVITY
The AD2S80A features an input protection circuit consisting of large “distributed” diodes and
polysilicon series resistors to dissipate both high energy discharges (Human Body Model) and
fast, low energy pulses (Charges Device Model).
The AD2S80A is ESD protection Class II (2000 V min). Proper ESD precautions are strongly
recommended to avoid functional damage or performance degradation. For further information
on ESD precautions, refer to Analog Devices ESD Prevention Manual.
–4–
WARNING!
ESD SENSITIVE DEVICE
REV. A
AD2S80A
PIN CONFIGURATIONS
RECOMMENDED OPERATING CONDITIONS
Power Supply Voltage (+VS, –VS) . . . . . . . . . ± 12 V dc ± 10%
Power Supply Voltage VL . . . . . . . . . . . . . . . . . +5 V dc ± 10%
Analog Input Voltage (SIN and COS) . . . . . . . 2 V rms ± 10%
Analog Input Voltage (REF) . . . . . . . . . . . . . . 1 V to 8 V peak
Signal and Reference Harmonic Distortion . . . . . . . 10% (max)
Phase Shift Between Signal and Reference . . . ± 10 Degrees (max)
Ambient Operating Temperature Range
Commercial (JD, KD, LD) . . . . . . . . . . . . . . 0°C to +70°C
Industrial (AD, BD) . . . . . . . . . . . . . . . . . . . –40°C to +85°C
Extended (SD, SE, TD, TE, UD, UE) . . . –55°C to +125°C
REFERENCE I/P 1
40 DEMOD O/P
39 INTEGRATOR O/P
DEMOD I/P 2
DIP (D) Package
AC ERROR O/P 3
38 INTEGRATOR I/P
COS 4
37 VCO I/P
36 –VS
ANALOG GND 5
35 RIPPLE CLK
SIGNAL GND 6
SIN
7
34 DIRECTION
+VS 8
33 BUSY
MSB DB1 9
DB2 10
32 DATA LOAD
AD2S80A
31 SC2
TOP VIEW
DB3 11 (Not to Scale) 30 SC1
ABSOLUTE MAXIMUM RATINGS l (with respect to GND)
DB4 12
+VS2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +14 V dc
–VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –14 V dc
+VL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +VS
Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +14 V to –VS
SIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +14 V to –VS
COS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +14 V to –VS
Any Logical Input .. . . . . . . . . . . . . . . . . . . –0.4 V dc to +VL dc
Demodulator Input . . . . . . . . . . . . . . . . . . . . . . . +14 V to –VS
Integrator Input . . . . . . . . . . . . . . . . . . . . . . . . . . +14 V to –VS
VCO Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +14 V to –VS
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860 mW
Operating Temperature
Commercial (JD, KD, LD) . . . . . . . . . . . . . . 0°C to +70°C
Industrial (AD, BD) . . . . . . . . . . . . . . . . . . . –40°C to +85°C
Extended (SD, SE, TD, TE, UD, UE) . . . –55°C to +125°C
θJC3 (40-Pin DIP 883 Parts Only) . . . . . . . . . . . . . . . . 11°C/W
θJC3 (44-Pin LCC 883 Parts Only) . . . . . . . . . . . . . . . . 10°C/W
Storage Temperature (All Grades) . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . . +300°C
29 DIGITAL GND
DB5 13
28 INHIBIT
DB6 14
27 BYTE SELECT
DB7 15
26 ENABLE
DB8 16
25 VL
24 DB16 LSB
INTEGRATOR I/P
INTEGRATOR O/P
21 DB13
2
1 44 43 42 41 40
NC
3
VCO I/P
4
DEMOD O/P
DEMOD I/P
22 DB14
DB12 20
REFERENCE I/P
DB11 19
COS
6 5
23 DB15
AC ERROR O/P
SIGNAL GND
ANALOG GND
DB9 17
DB10 18
SIN 7
39 –VS
+VS 8
38 RIPPLE CLOCK
NC 9
37 DIRECTION
MSB DB1 10
36 BUSY
DB2 11
AD2S80A
35 DATA LOAD
DB3 12
TOP VIEW
(Not to Scale)
34 NC
DB4 13
CAUTION:
1. Absolute Maximum Ratings are those values beyond which damage to the device
may occur.
2. Correct polarity voltages must be maintained on the +V S and –VS pins.
3. With reference to Appendix C of MIL-M-38510.
LCC (E) Package
33 SC2
DB5 14
32 SC1
DB6 15
31 DIGITAL GND
DB7 16
30 INHIBIT
DB8 17
29 NC
BYTE SELECT
+VL
ENABLE
DB15
DB14
LSB DB16
NC = NO CONNECT
DB13
DB11
DB12
DB9
DB10
18 19 20 21 22 23 24 25 26 27 28
Bit Weight Table
Binary
Bits (N)
Resolution
(2N)
Degrees
/Bit
360.0
180.0
90.0
45.0
22.5
Minutes
/Bit
0
1
2
3
4
1
2
4
8
16
5
6
7
8
9
32
64
128
256
512
10
11
12
13
14
1024
2048
4096
8192
116384
0.3515625
0.1757813
0.0878906
0.0439453
0.0219727
21.09375
10.546875
5.273438
2.636719
1.318359
1265.625
632.8125
316.40625
158.20313
79.10156
15
16
17
18
32768
65536
131072
262144
0.0109836
0.0054932
0.0027466
0.0013733
0.659180
0.329590
0.164795
0.082397
39.55078
19.77539
9.88770
4.94385
11.25
5.625
2.8125
1.40625
0.703125
21600.0
10800.0
5400.0
2700.0
1350.0
675.0
337.5
168.75
84.375
42.1875
PIN DESIGNATIONS
Seconds
/Bit
1296000.0
648000.0
324000.0
162000.0
81000.0
40500.0
20250.0
10125.0
5062.5
2531.25
MNEMONIC
DESCRIPTION
REFERENCE I/P
DEMOD I/P
AC ERROR O/P
COS
ANALOG GROUND
SIGNAL GROUND
SIN
+VS
DB1–DB16
VL
ENABLE
REFERENCE SIGNAL INPUT
DEMODULATOR INPUT
RATIO MULTIPLIER OUTPUT
COSINE INPUT
POWER GROUND
RESOLVER SIGNAL GROUND
SINE INPUT
POSITIVE POWER SUPPLY
PARALLEL OUTPUT DATA
LOGIC POWER SUPPLY
LOGIC Hl-OUTPUT DATA IN HIGH IMPEDANCE
STATE, LOGIC LO PRESENTS DATA TO THE
OUTPUT LATCHES
LOGIC Hl-MOST SIGNIFICANT BYTE TO DB1–DB8
LOGIC LO-LEAST SlGNlFlCANT BYTE TO DB1–DB8
LOGIC LO INHIBITS DATA TRANSFER TO
OUTPUT LATCHES
DlGITAL GROUND
SELECT CONVERTER RESOLUTION
LOGIC LO DB1–DB16 INPUTS LOGIC Hl DB1–D16
OUTPUTS
CONVERTER BUSY, DATA NOT VALID WHILE
BUSY Hl
LOGIC STATE DEFINES DIRECTION
OF INPUT SIGNAL ROTATION
POSITIVE PULSE WHEN CONVERTER OUTPUT
CHANGES FROM 1S TO ALL 0S OR VICE VERSA
NEGATIVE POWER SUPPLY
VCO INPUT
INTEGRATOR INPUT
INTEGRATOR OUTPUT
DEMODULATOR OUTPUT
BYTE SELECT
INHIBIT
DIGITAL GROUND
SC1–SC2
DATA LOAD
BUSY
DIRECTION
RIPPLE CLOCK
REV. A
–VS
VCO I/P
INTEGRATOR I/P
INTEGRATOR O/P
DEMOD O/P
–5–
AD2S80A
CONNECTING THE CONVERTER
SIGNAL GROUND and ANALOG GROUND are connected
internally. ANALOG GROUND and DIGITAL GROUND
must be connected externally.
The power supply voltages connected to +VS and –VS pins
should be +12 V dc and –12 V dc and must not be reversed.
The voltage applied to VL can be +5 V dc to +VS.
The external components required should be connected as
shown in Figure 1.
It is recommended that the decoupling capacitors are connected
in parallel between the power lines +VS, –VS and ANALOG
GROUND adjacent to the converter. Recommended values are
100 nF (ceramic) and 10 µF (tantalum). Also capacitors of
100 nF and 10 µF should be connected between +VL and
DIGITAL GROUND adjacent to the converter.
CONVERTER RESOLUTION
Two major areas of the AD2S80A specification can be selected
by the user to optimize the total system performance. The resolution of the digital output is set by the logic state of the inputs
SC1 and SC2 to be 10, 12, 14 or 16 bits; and the dynamic characteristics of bandwidth and tracking rate are selected by the
choice of external components.
When more than one converter is used on a card, then separate
decoupling capacitors should be used for each converter.
The resolver connections should be made to the SIN and COS
inputs, REFERENCE INPUT and SIGNAL GROUND as
shown in Figure 7 and described in section “CONNECTING
THE RESOLVER.”
The choice of the resolution will affect the values of R4 and R6
which scale the inputs to the integrator and the VCO respectively (see section COMPONENT SELECTION). If the resolution is changed, then new values of R4 and R6 must be switched
into the circuit.
The two signal ground wires from the resolver should be joined
at the SIGNAL GROUND pin of the converter to minimize the
coupling between the sine and cosine signals. For this reason it
is also recommended that the resolver is connected using individually screened twisted pair cables with the sine, cosine and
reference signals twisted separately.
Note: When changing resolution under dynamic conditions, do
it when the BUSY is low, i.e., when Data is not changing.
REFERENCE
I/P
HF FILTER
OFFSET ADJUST
R9
+12V
–12V
C3
R8
R2
C1
R3
BANDWIDTH
SELECTION
C2
R4
R1
DEMOD
I/P
SIN
SIG GND
A1
COS
A2
SEGMENT
SWITCHING
R-2R DAC
RIPPLE
CLK
C4
DEMOD
O/P
R5
PHASE
SENSITIVE
DETECTOR
A3
VELOCITY
SIGNAL
INTEGRATOR
O/P
AD2S80A
GND
R6
16-BIT UP/DOWN COUNTER
VCO + DATA
TRANSFER LOGIC
+12V
–12V
C5
INTEGRATOR
I/P
AC ERROR O/P
OUTPUT DATA LATCH
VCO
I/P
TRACKING
RATE
SELECTION
R7
C6
DATA SC1 SC2
LOAD
ENABLE
16 DATA BITS
BYTE +5V
SELECT
DIG
GND
BUSY
DIRN INHIBIT
Figure 1. AD2S80A Connection Diagram
–6–
REV. A
AD2S80A
CONVERTER OPERATION
POSITION OUTPUT
When connected in a circuit such as shown in Figure 1 the
AD2S80A operates as a tracking resolver-to-digital converter
and forms a Type 2 closed-loop system. The output will automatically follow the input for speeds up to the selected maximum tracking rate. No convert command is necessary as the
conversion is automatically initiated by each LSB increment, or
decrement, of the input. Each LSB change of the converter initiates a BUSY pulse.
The resolver shaft position is represented at the converter output by a natural binary parallel digital word. As the digital position output of the converter passes through the major carries,
i.e., all “1s” to all “0s” or the converse, a RIPPLE CLOCK
(RC) logic output is initiated indicating that a revolution or a
pitch of the input has been completed.
The direction of input rotation is indicated by the DIRECTION
(DIR) logic output. This direction data is always valid in advance of a RIPPLE CLOCK pulse and, as it is internally
latched, only changing state (1 LSB min change) with a corresponding change in direction.
The AD2S80A is remarkably tolerant of input amplitude and
frequency variation because the conversion depends only on the
ratio of the input signals. Consequently there is no need for accurate, stable oscillator to produce the reference signal. The inclusion of the phase sensitive detector in the conversion loop
ensures a high immunity to signals that are not coherent or are
in quadrature with the reference signal.
Both the RIPPLE CLOCK pulse and the DIRECTION data
are unaffected by the application of the INHIBIT. The static
positional accuracy quoted is the worst case error that can occur
over the full operating temperature excluding the effects of offset signals at the INTEGRATOR INPUT (which can be
trimmed out—see Figure 1), and with the following conditions:
input signal amplitudes are within 10% of the nominal; phase
shift between signal and reference is less than 10 degrees.
SIGNAL CONDITIONING
The amplitude of the SINE and COSINE signal inputs should
be maintained within 10% of the nominal values if full performance is required from the velocity signal.
These operating conditions are selected primarily to establish a
repeatable acceptance test procedure which can be traced to national standards. In practice, the AD2S80A can be used well
outside these operating conditions providing the above points
are observed.
The digital position output is relatively insensitive to amplitude
variation. Increasing the input signal levels by more than 10%
will result in a loss in accuracy due to internal overload. Reducing levels will result in a steady decline in accuracy. With the
signal levels at 50% of the correct value, the angular error will
increase to an amount equivalent to 1.3 LSB. At this level the
repeatability will also degrade to 2 LSB and the dynamic response will also change, since the dynamic characteristics are
proportional to the signal level.
VELOCITY SIGNAL
The tracking converter technique generates an internal signal at
the output of the integrator (the INTEGRATOR OUTPUT
pin) that is proportional to the rate of change of the input angle.
This is a dc analog output referred to as the VELOCITY signal.
The AD2S80A will not be damaged if the signal inputs are
applied to the converter without the power supplies and/or the
reference.
In many applications it is possible to use the velocity signal of
the AD2S80A to replace a conventional tachogenerator.
REFERENCE INPUT
DC ERROR SIGNAL
The amplitude of the reference signal applied to the converter’s
input is not critical, but care should be taken to ensure it is kept
within the recommended operating limits.
The signal at the output of the phase sensitive detector (DEMODULATOR OUTPUT) is the signal to be nulled by the
tracking loop and is, therefore, proportional to the error between the input angle and the output digital angle. This is the
dc error of the converter; and as the converter is a Type 2 servo
loop, it will increase if the output fails to track the input for any
reason. It is an indication that the input has exceeded the maximum tracking rate of the converter or, due to some internal
malfunction, the converter is unable to reach a null. By connecting two external comparators, this voltage can be used as a
“built-in-test.”
The AD2S80A will not be damaged if the reference is supplied
to the converter without the power supplies and/or the signal
inputs.
HARMONIC DISTORTION
The amount of harmonic distortion allowable on the signal and
reference lines is 10%.
Square waveforms can be used but the input levels should be
adjusted so that the average value is 1.9 V rms. (For example, a
square wave should be 1.9 V peak.) Triangular and sawtooth
waveforms should have a amplitude of 2 V rms.
Note: The figure specified of 10% harmonic distortion is for
calibration convenience only.
REV. A
–7–
AD2S80A
4. Maximum Tracking Rate (R6)
The VCO input resistor R6 sets the maximum tracking rate
of the converter and hence the velocity scaling as at the max
tracking rate, the velocity output will be 8 V.
COMPONENT SELECTION
The following instructions describe how to select the external
components for the converter in order to achieve the required
bandwidth and tracking rate. In all cases the nearest “preferred
value” component should be used, and a 5% tolerance will not
degrade the overall performance of the converter. Care should
be taken that the resistors and capacitors will function over the
required operating temperature range. The components should
be connected as shown in Figure 1.
Decide on your maximum tracking rate, “T,” in revolutions
per second. Note that “T” must not exceed the maximum
tracking rate or 1/16 of the reference frequency.
10
R6 =
PG compatible software is available to help users select the optimum
component values for the AD2S80A, and display the transfer gain,
phase and small step response.
1. HF Filter (R1, R2, C1, C2)
The function of the HF filter is to remove any dc offset and
to reduce the amount of noise present on the signal inputs to
the AD2S80A, reaching the Phase Sensitive Detector and affecting the outputs. R1 and C2 may be omitted—in which
case R2 = R3 and C1 = C3, calculated below—but their use
is particularly recommended if noise from switch mode power
supplies and brushless motor drive is present.
Resolution
10
12
14
16
15 kΩ ≤ R1 = R2 ≤ 56 kΩ
Ratio of Reference Frequency/Bandwidth
2.5 : 1
4 :1
6 :1
7.5 : 1
Typical values may be 100 Hz for a 400 Hz reference frequency and 500 Hz to 1000 Hz for a 5 kHz reference
frequency.
1
2 π R1 fREF
b. Select C4 so that
and fREF = Reference frequency
(Hz)
C4 =
This filter gives an attenuation of three times at the input to
the phase sensitive detector.
21
F
R6 × fBW 2
with R6 in Ω and fBW, in Hz selected above.
2. Gain Scaling Resistor (R4)
If R1, C2 arc fitted then:
c. C5 is given by
R5 =
where 100 × 10–9 = current/LSB
If R1, C2 are not fitted then:
EDC
100 × 10
–9
Ω
2 × π × f BW × C5
Ω
C6 = 470 pF, R7 = 68 Ω
where EDC = 160 × 10 for 10 bits resolution
7. Offset Adjust
Offsets and bias currents at the integrator input can cause an
additional positional offset at the output of the converter of 1
arc minute typical, 5.3 arc minutes maximum. If this can be
tolerated, then R8 and R9 can be omitted from the circuit.
= 40 × 10–3 for 12 bits
= 10 × 10–3 for 14 bits
= 2.5 × 10–3 for 16 bits
= Scaling of the DC ERROR in volts
If fitted, the following values of R8 and R9 should be used:
R8 = 4.7 MΩ, R9 = 1 MΩ potentiometer
3. AC Coupling of Reference Input (R3, C3)
Select R3 and C3 so that there is no significant phase shift at
the reference frequency. That is,
To adjust the zero offset, ensure the resolver is disconnected
and all the external components are fitted. Connect the COS
pin to the REFERENCE INPUT and the SIN pin to the
SIGNAL GROUND and with the power and reference applied, adjust the potentiometer to give all “0s” on the digital
output bits.
The potentiometer may be replaced with select on test resistors if preferred.
R3 = 100 kΩ
R3 × fREF
4
6. VCO Phase Compensation
The following values of C6 and R7 should be fitted.
–3
1
C5 = 5 × C4
d. R5 is given by
E DC
1
R4 =
× Ω
–9
100 ×10
3
C3 >
Ω
5. Closed-Loop Bandwidth Selection (C4, C5, R5)
a. Choose the closed-loop bandwidth (fBW) required
ensuring that the ratio of reference frequency to bandwidth does not exceed the following guidelines:
Values should be chosen so that
R4 =
T ×n
where n = bits per revolution
= 1,024 for 10 bits resolution
= 4,096 for 12 bits
= 16,384 for 14 bits
= 65,536 for 16 bits
For more detailed information and explanation, see section “CIRCUIT FUNCTIONS AND DYNAMIC PERFORMANCE.”
C1 = C2
6. 32 × 10
F
with R3 in Ω.
–8–
REV. A
AD2S80A
DATA TRANSFER
+5V
To transfer data the INHIBIT input should be used. The data
will be valid 600 ns after the application of a logic “LO” to the
INHIBIT. This is regardless of the time when the INHIBIT is
applied and allows time for an active BUSY to clear. By using
the ENABLE input the two bytes of data can be transferred after which the INHIBIT should be returned to a logic “HI” state
to enable the output latches to be updated.
1k
10k
TO COUNTER
(CLOCK)
IN4148
RIPPLE
CLOCK
2N3904
+5V
0V
5k1
IN4148
BUSY
NOTE: DO NOT USE ABOVE CCT WHEN INHIBIT IS "LO."
BUSY Output
Figure 2. Diode Transistor Logic Nand Gate
The validity of the output data is indicated by the state of the
BUSY output. When the input to the converter is changing, the
signal appearing on the BUSY output is a series of pulses at
TTL level. A BUSY pulse is initiated each time the input moves
by the analog equivalent of one LSB and the internal counter is
incremented or decremented.
DIRECTION Output
The DIRECTION (DIR) logic output indicates the direction of
the input rotation. Any change in the state of DIR precedes the
corresponding BUSY, DATA and RIPPLE CLOCK updates.
DIR can be considered as an asynchronous output and can
make multiple changes in state between two consecutive LSB
update cycles. This corresponds to a change in input rotation
direction but less than 1 LSB.
INHIBIT Input
The INHIBIT logic input only inhibits the data transfer from
the up-down counter to the output latches and, therefore, does
not interrupt the operation of the tracking loop. Releasing the
INHIBIT automatically generates a BUSY pulse to refresh the
output data.
DIGITAL TIMING
VH
BUSY
t1
ENABLE Input
VL
RIPPLE
CLOCK
The ENABLE input determines the state of the output data. A
logic “HI” maintains the output data pins in the high impedance condition, and the application of a logic “LO” presents the
data in the latches to the output pins. The operation of the
ENABLE has no effect on the conversion process.
VH
t2
t4
VH
t5
VL
t3
DATA
BYTE SELECT Input
INHIBIT
The BYTE SELECT input selects the byte of the position data
to be presented at the data output DB1 to DB8. The least significant byte will be presented on data output DB9 to DB16
(with the ENABLE input taken to a logic “LO”) regardless of
the state of the BYTE SELECT pin. Note that when the
AD2S80A is used with a resolution less than 16 bits the unused
data lines are pulled to a logic “LO.” A logic “HI” on the BYTE
SELECT input will present the eight most significant data bits
on data output DB1 and DB8. A logic “LO” will present the
least significant byte on data outputs 1 to 8, i.e., data outputs 1
to 8 will duplicate data outputs 9 to 16.
VH
VH
t6
t7
DIR
VL
t8
INHIBIT
t9
VL
VL
ENABLE
VZ
DATA
The operation of the BYTE SELECT has no effect on the conversion process of the converter.
t 10
VH
t11
VL
VL
BYTE
SELECT
VH
VH
RIPPLE CLOCK
DATA
As the output of the converter passes through the major carry,
i.e., all “1s” to all “0s” or the converse, a positive going edge on
the RIPPLE CLOCK (RC) output is initiated indicating that a
revolution, or a pitch, of the input has been completed.
t12
The minimum pulse width of the ripple clock is 300 ns.
RIPPLE CLOCK is normally set high before a BUSY pulse and
resets before the next positive going edge of the next consecutive
pulse.
The only exception to this is when DIR changes whist the
RIPPLE CLOCK is high. Resetting of the RIPPLE clock will
only occur if the DIR remains stable for two consecutive positive BUSY pulse edges.
If the AD2S80A is being used in a pitch and revolution counting application, the ripple and busy will need to be gated to prevent false decrement or increment (see Figure 2).
RIPPLE CLOCK is unaffected by INHIBIT.
REV. A
–9–
t13
VL
PARAMETER
TMIN
TMAX
CONDITION
t1
200
600
BUSY WIDTH VH–VH
t2
10
25
RIPPLE CLOCK VH TO BUSY VH
t3
470
580
RIPPLE CLOCK VL TO NEXT BUSY VH
t4
16
45
BUSY VH TO DATA VH
t5
3
25
BUSY VH TO DATA VL
t6
70
140
INHIBIT VH TO BUSY VH
t7
485
625
MIN DIR VH TO BUSY VH
t8
515
670
MIN DIR VH TO BUSY VH
t9
–
600
INHIBIT VL TO DATA STABLE
t10
40
110
ENABLE VL TO DATA VH
t11
35
110
ENABLE VL TO DATA VL
t12
60
140
BYTE SELECT VL TO DATA STABLE
t13
60
125
BYTE SELECT VH TO DATA STABLE
AD2S80A
CIRCUIT FUNCTIONS AND DYNAMIC PERFORMANCE
Additional compensation in the form of a pole/zero pair is required to stabilize any Type 2 loop to avoid the loop gain characteristic crossing the 0 dB axis with 180° of additional phase
lag, as shown in Figure 5.
The AD2S80A allows the user greater flexibility in choosing the
dynamic characteristics of the resolver-to-digital conversion to
ensure the optimum system performance. The characteristics
are set by the external components shown in Figure 1, and the
section “COMPONENT SELECTION” explains how to select
desired maximum tracking rate and bandwidth values. The following paragraphs explain in greater detail the circuit of the
AD2S80A and the variations in the dynamic performance available to the user.
This compensation is implemented by the integrator components (R4, C4, R5, C5).
The overall response of such a system is that of a unity gain second order low pass filter, with the angle of the resolver as the input and the digital position data as the output.
Loop Compensation
The AD2S80A (connected as shown in Figure 1) operates as a
Type 2 tracking servo loop where the VCO/counter combination
and Integrator perform the two integration functions inherent in
a Type 2 loop.
The AD2S80A does not have to be connected as tracking converter, parts of the circuit can be used independently. This is
particularly true of the Ratio Multiplier which can be used as a
control transformer (see Application Note).
A block diagram of the AD2S80A is given in Figure 3.
R5 C5
AC ERROR
sin θ sin ωt
RATIO
MULTIPLIER
cos θ sin ωt
C4
A1 sin (θ – φ) sin ωt
PHASE
SENSITIVE
DEMODULATOR
R4
INTEGRATOR
CLOCK
R6
VCO
DIRECTION
DIGITAL
φ
VELOCITY
Figure 3. Functional Diagram
Ratio Multiplier
The ratio multiplier is the input section of the AD2S80A and
compares the signal from the resolver input angle, θ, to the
digital angle, φ, held in the counter. Any difference between
these two angles results in an analog voltage at the AC ERROR
OUTPUT. This circuit function has historically been called
a “Control Transformer” as it was originally performed by an
electromechanical device known by that name.
The AC ERROR signal is given by
A1 sin (θ–φ) sin ωt
where ω = 2 π fREF
fREF = reference frequency
A1, the gain of the ratio multiplier stage is 14.5.
So for 2 V rms inputs signals
AC ERROR output in volts/(bit of error)
 360 
= 2 × sin  n  × A1


where n = bits per rev
= 1,024 for 10 bits resolution
= 4,096 for 12 bits
= 16,384 for 14 bits
= 65,536 for 16 bits
giving an AC ERROR output
= 178 mV/bit @ 10 bits resolution
= 44.5 mV/bit @ 12 bits
= 11.125 mV/bit @ 14 bits
= 2.78 mV/bit @ 16 bits
The ratio multiplier will work in exactly the same way whether
the AD2S80A is connected as a tracking converter or as a control transformer, where data is preset into the counters using the
DATA LOAD pin.
HF Filter
The AC ERROR OUTPUT may be fed to the PSD via a simple
ac coupling network (R2, C1) to remove any dc offset at this
point. Note, however, that the PSD of the AD2S80A is a
wideband demodulator and is capable of aliasing HF noise
down to within the loop bandwidth. This is most likely to happen where the resolver is situated in particularly noisy environments, and the user is advised to fit a simple HF filter R1, C2
prior to the phase sensitive demodulator.
The attenuation and frequency response of a filter will affect the
loop gain and must be taken into account in deriving the loop
transfer function. The suggested filter (R1, C1, R2, C2) is
shown in Figure 1 and gives an attenuation at the reference
frequency (fREF) of 3 times at the input to the phase sensitive
demodulator .
Values of components used in the filter must be chosen to ensure that the phase shift at fREF is within the allowable signal to
reference phase shift of the converter.
Phase Sensitive Demodulator
The phase sensitive demodulator is effectively ideal and develops a mean dc output at the DEMODULATOR OUTPUT
pin of
±2 2
π × (DEMODULATOR INPUT rms voltage )
–10–
REV. A
AD2S80A
for sinusoidal signals in phase or antiphase with the reference
(for a square wave the DEMODULATOR OUTPUT voltage
will equal the DEMODULATOR INPUT). This provides a signal at the DEMODULATOR OUTPUT which is a dc level
proportional to the positional error of the converter.
DC Error Scaling = 160 mV/bit (10 bits resolution)
= 40 mV/bit (12 bits resolution)
= 10 mV/bit (14 bits resolution)
= 2.5 mV/bit (16 bits resolution)
The tracking rate in rps per µA of VCO input current can be
found by dividing the VCO scaling factor by the number of LSB
changes per rev (i.e., 4096 for 12-bit resolution).
The input resistor R6 determines the scaling between the converter velocity signal voltage at the INTEGRATOR OUTPUT
pin and the VCO input current. Thus to achieve a 5 V output at
100 rps (6000 rpm) and 12-bit resolution the VCO input current must be:
(100 × 4096)/(7900) = 51.8 µA
When the tracking loop is closed, this error is nulled to zero unless the converter input angle is accelerating.
Thus, R6 would be set to: 5/(51.8 × 10–6) = 96 kΩ
Integrator
The velocity offset voltage depends on the VCO input resistor,
R6, and the VCO bias current and is given by
The integrator components (R4, C4, R5, C5) are external to the
AD2S80A to allow the user to determine the optimum dynamic
characteristics for any given application. The section “COMPONENT SELECTION” explains how to select components for a
chosen bandwidth.
Since the output from the integrator is fed to the VCO INPUT,
it is proportional to velocity (rate of change of output angle) and
can be scaled by selection of R6, the VCO input resistor. This is
explained in the section “VOLTAGE CONTROLLED OSCILLATOR (VCO)” below.
To prevent the converter from “flickering” (i.e., continually
toggling by ± 1 bit when the quantized digital angle, φ, is not an
exact representation of the input angle, θ) feedback is internally
applied from the VCO to the integrator input to ensure that the
VCO will only update the counter when the error is greater than
or equal to 1 LSB. In order to ensure that this feedback “hysteresis” is set to 1 LSB the input current to the integrator must
be scaled to be 100 nA/bit. Therefore,
R4 =
The temperature coefficient of this offset is given by
Velocity Offset Tempco = R6 × (VCO bias current tempco)
where the VCO bias current tempco is typically –1.22 nA/°C.
The maximum recommended rate for the VCO is 1.1 MHz
which sets the maximum possible tracking rate.
Since the minimum voltage swing available at the integrator
output is ± 8 V, this implies that the minimum value for R6 is
57 kΩ. As
Max Current =
MinValue R6
100 (nA /bit )
Any offset at the input of the integrator will affect the accuracy
of the conversion as it will be treated as an error signal and offset the digital output. One LSB of extra error will be added for
each 100 nA of input bias current. The method of adjusting out
this offset is given in the section “COMPONENT SELECTION.”
Voltage Controlled Oscillator (VCO)
The VCO is essentially a simple integrator feeding a pair of dc
level comparators. Whenever the integrator output reaches one
of the comparator threshold voltages, a fixed charge is injected
into the integrator input to balance the input current. At the
same time the counter is clocking either up or down, dependent
on the polarity of the input current. In this way the counter is
clocked at a rate proportional to the magnitude of the input current of the VCO.
During the reset period the input continues to be integrated, the
reset period is constant at 400 ns.
6
3
= 139 µA
–6
= 57 kΩ
7.9 × 10
8
139 × 10
By selecting components using the method outlined in the section “Component Selection,” the converter will have a critically
damped time response and maximum phase margin. The
Closed-Loop Transfer Function is given by:
θOUT
14 (1+ sN )
=
2
θ IN
(sN + 2.4)(sN + 3.4 sN + 5.8)
where, sN, the normalized frequency variable is:
2 s
sN = π
f BW
and fBW is the closed-loop 3 dB bandwidth (selected by the
choice of external components).
The acceleration KA, is given approximately by
2
K A = 6 × ( f BW ) sec
–2
The normalized gain and phase diagrams are given in Figures 4
and 5.
= 7.9 kHz/µA
REV. A
1.1 × 10
Transfer Function
DC Error Scaling (mV /bit )
The VCO rate is fixed for a given input current by the VCO
scaling factor:
Velocity Offset Voltage = R6 × (VCO bias current)
–11–
AD2S80A
The small signal step response is shown in Figure 6. The time
from the step to the first peak is t1 and the t2 is the time from
the step until the converter is settled to 1 LSB. The times t1 and
t2 are given approximately by
12
9
GAIN PLOT
6
3
t1 =
0
–3
t2 =
–6
–9
f BW
5
R
×
f BW 12
where R = resolution, i.e., 10, 12, 14 or 16.
–12
0.02fBW
0.04fBW
0.1fBW
0.2fBW
0.4fBW
fBW
2fBW
FREQUENCY
Figure 4. AD2S80A Gain Plot
The large signal step response (for steps greater than 5 degrees)
applies when the error voltage exceeds the linear range of the
converter.
Typically the converter will take 3 times longer to reach the first
peak for a 179 degrees step.
In response to a velocity step, the velocity output will exhibit the
same time response characteristics as outlined above for the position output.
180
135
90
PHASE PLOT
1
ACCELERATION ERROR
A tracking converter employing a Type 2 servo loop does not
suffer any velocity lag, however, there is an additional error due
to acceleration. This additional error can be defined using the
acceleration constant KA of the converter.
45
0
–45
KA =
–90
–135
–180
0.02fBW
0.04fBW
0.1fBW
0.2fBW
0.4fBW
fBW
2fBW
FREQUENCY
Figure 5. AD2S80A Phase Plot
OUTPUT
POSITION
t2
Input Acceleration
Error in Output Angle
The numerator and denominator must have consistent angular
units. For example if KA is in sec-2, then the input acceleration
may be specified in degrees/sec2 and the error output in degrees.
Angular measurement may also be specified using radians, minutes of arc, LSBs, etc.
KA does not define maximum input acceleration, only the error due
to it’s acceleration. The maximum acceleration allowable before
the converter loses track is dependent on the angular accuracy
requirements of the system.
Angular Accuracy × KA = Degrees/sec2
KA can be used to predict the output position error for a
given input acceleration. For example for an acceleration of
100 revs/sec2, KA = 2.7 × 106 sec-2 and 12-bit resolution.
Error in LSBs =
Input acceleration [LSB/sec 2 ]
K A[sec –2 ]
100 [rev/sec 2 ] × 212
= 0.15 LSBs or 47.5 seconds of arc
2.7×10 6
To determine the value of KA based on the passive components
used to define the dynamics of the converter the following
should be used.
=
TIME
t1
Figure 6. AD2S80A Small Step Response
KA =
2n
4.04 ×1011
• R6• R4 •(C4 + C5)
Where n = resolution of the converter.
R4, R6 in ohms
C5, C4 in farads
–12–
REV. A
AD2S80A
VELOCITY ERRORS
SOURCES OF ERRORS
Integrator Offset
The signal at the INTEGRATOR OUTPUT pin relative to the
ANALOG GROUND pin is an analog voltage proportional to
the rate of change of the input angle. This signal can be used to
stabilize servo loops or in the place of a velocity transducer. Although the conversion loop of the AD2S80A includes a digital
section there is an additional analog feedback loop around the
velocity signal. This ensures against flicker in the digital positional output in both dynamic and static states.
Additional inaccuracies in the conversion of the resolver signals
will result from an offset at the input to the integrator as it will
be treated as an error signal. This error will typically be 1 arc
minute over the operating temperature range.
A description of how to adjust from zero offset is given in the
section “COMPONENT SELECTION” and the circuit required is shown in Figure 1.
Differential Phase Shift
Phase shift between the sine and cosine signals from the resolver
is known as differential phase shift and can cause static error.
Some differential phase shift will be present on all resolvers as a
result of coupling. A small resolver residual voltage (quadrature
voltage) indicates a small differential phase shift. Additional phase
shift can be introduced if the sine channel wires and the cosine
channel wires are treated differently. For instance, different cable
lengths or different loads could cause differential phase shift .
The additional error caused by differential phase shift on the input signals approximates to
Error = 0.53 a × b arc minutes
where a = differential phase shift (degrees).
b = signal to reference phase shift (degrees).
This error can be minimized by choosing a resolver with a small
residual voltage, ensuring that the sine and cosine signals are
handled identically and removing the reference phase shift (see
section “CONNECTING THE RESOLVER”). By taking these
precautions the extra error can be made insignificant.
A better quality velocity signal will be achieved if the following
points are considered:
1. Protection.
The velocity signal should be buffered before use.
2. Reversion error.1
The reversion error can be nulled by varying one supply rail
relative to the other.
3. Ripple and Noise.
Noise on the input signals to the converter is the major cause of
noise on the velocity signal. This can be reduced to a minimum
if the following precautions are taken:
The resolver is connected to the converter using separate
twisted pair cable for the sine, cosine and reference signals.
Care is taken to reduce the external noise wherever possible.
An HF filter is fltted before the Phase Sensitive Demodulator
(as described in the section HF FILTER).
A resolver is chosen that has low residual voltage, i.e., a small
signal in quadrature with the reference.
Under static operating conditions phase shift between the reference and the signal lines alone will not theoretically affect the
converter’s static accuracy.
Components are selected to operate the AD2S80A with the
lowest acceptable bandwidth.
Feedthrough of the reference frequency should be removed by
a filter on the velocity signal.
However, most resolvers exhibit a phase shift between the signal
and the reference. This phase shift will give rise under dynamic
conditions to an additional error defined by:
Maintenance of the input signal voltages at 2 V rms will prevent LSB flicker at the positional output. The analog feedback or hysteresis employed around the VCO and the
intergrator is a function of the input signal levels (see section
“INTEGRATOR”) .
Shaft Speed (rps) × Phase Shift (Degrees )
Reference Frequency
For example, for a phase shift of 20 degrees, a shaft rotation of
22 rps and a reference frequency of 5 kHz, the converter will exhibit an additional error of:
22 × 20
0.088 Degrees
5000
Following the preceding precautions will allow the user to use
the velocity signal in very noisy environments, for example,
PWM motor drive applications. Resolver/converter error curves
may exhibit apparent acceleration/deceleration at a constant velocity. This results in ripple on the velocity signal of frequency
twice the input rotation.
This effect can be eliminated by placing a phase shift in the reference to the converter equivalent to the phase shift in the resolver (see section “CONNECTING THE RESOLVER”).
Note: Capacitive and inductive crosstalk in the signal and reference
leads and wiring can cause similar problems.
1
Reversion error, or side-to-side nonlinearity, is a result of differences in the
up and down rates of the VCO.
REV. A
–13–
AD2S80A
CONNECTING THE RESOLVER
TYPICAL CIRCUIT CONFIGURATION
The recommended connection circuit is shown in Figure 7.
Figure 8 shows a typical circuit configuration for the AD2S80A
in a 12-bit resolution mode. Values of the external components
have been chosen for a reference frequency of 5 kHz and a
maximum tracking rate of 260 rps with a bandwidth of 520 Hz.
Placing the values for R4, R6, C4 and C5 in the equation for KA
gives a value of 2.7 × 106. The resistors are 0.125 W, 5% tolerance preferred values. The capacitors are 100 V ceramic, 10%
tolerance components.
In cases where the reference phase relative to the input signals
from the resolver requires adjustment, this can be easily
achieved by varying the value of the resistor R2 of the HF filter
(see Figure 1).
Assuming that R1 = R2 = R and C1 = C2 = C
1
and Reference Frequency = 2 π RC
by altering the value of R2, the phase of the reference relative to
the input signals will change in an approximately linear manner
for phase shifts of up to 10 degrees.
Increasing R2 by 10% introduces a phase lag of 2 degrees. Decreasing R2 by 10% introduces a phase lead of 2 degrees.
PHASE LEAD = ARC TAN
C
1
PHASE LAG = ARC TAN 2πfRC
2πfRC
R
R
C
Phase Shift Circuits
For signal and reference voltages greater than 2 V rms a simple
voltage divider circuit of resistors can be used to generate the
correct signal level at the converter. Care should be taken to ensure that the ratios of the resistors between the sine signal line
and ground and the cosine signal line and ground are the same.
Any difference will result in an additional position error.
For more information on resistive scaling of SIN, COS and
REFERENCE converter inputs refer to the application note,
“Circuit Applications of the 2S81 and 2S81 Resolver-to-Digital
Converters.”
RELIABILITY
The AD2S80A Mean Time Between Failures (MTBF) has been
calculated according to MIL-HDBK-217E, Figure 10 shows the
MTBF in hours in naval sheltered conditions for AD2S80A/
883B only.
OSCILLATOR
(e.g., OSC1758)
C3
1
R3
REF I/P
2
AD2S80A
3
TWISTED PAIR SCREENED CABLE
S2
S4
R1
S3
R2
S1
4
COS I/P
5
ANALOG
GND
6
SIGNAL
GND
7
SIN I/P
DIGITAL
GND
31
RESOLVER
POWER
RETURN
Figure 7. Connecting the AD2S80A to a Resolver
–14–
REV. A
AD2S80A
1MΩ
4.7MΩ
2.2nF
100kΩ
15kΩ
100nF
REFERENCE
INPUT
1
40
2
39
3
38
4
37
5
36
REF LOW
6
35 RIPPLE CLOCK
COS LOW
7
34 DIRECTION
SIN LOW
8
33 BUSY
SIN HIGH
9
100nF
2.2nF
15kΩ
COS HIGH
RESOLVER
SIGNALS
PIN 1
39
kΩ
MSB
10
+12V
DATA
OUTPUT
1.5
nF
110
kΩ
VELOCITY
O/P
6.8
nF
180kΩ
470pF
100nF
68Ω
–12V
32 DATA/LOAD
AD2S80A
31 SC2
TOP VIEW
11 (Not to Scale)
30
12
29
13
28 INHIBIT
14
27 BYTE SELECT
15
26
16
25
17
24
18
23
19
22
20
21
0V
100nF
ENABLE
+5V
LSB
Figure 8. Typical Circuit Configuration
10M
360
315
MTBF – Hours
ANGLE – Degrees
270
225
180
135
1M
100k
90
45
10k
0
4
8
12
16
20
–40
24
TIME – ms
Figure 9. Large Step Response Curves for Typical Circuit
Shown in Figure 8
REV. A
–20
0
20
40
60
TEMPERATURE – °C
80
100
Figure 10. AD2S80A MTBF Curve
–15–
120
AD2S80A
The ratio multiplier of the AD2S80A can be used independently
of the loop integrators as a control transformer. In this mode the
resolver inputs θ are multiplied by a digital angle φ any difference between φ and θ will be represented by the AC ERROR
output as SIN ωt sin (θ–φ) or the DEMOD output as sin (θ–φ).
To use the AD2S80A in this mode refer to the “Control Transformer” application note.
Dynamic Switching
In applications where the user requires wide band response from
the converter, for example 100 rpm to 6000 rpm, superior performance is achieved if the converters control characteristics are
switched dynamically. This reduces velocity offset levels at low
tracking rates. For more information on the technique refer to
“Dynamic Resolution Switching Using the Variable Resolution
Monolithic Resolver-to-Digital Converters.”
OTHER PRODUCTS
The AD2S82A is a monolithic, variable resolution 10-, 12-, 14and 16-bit resolver-to-digital converter in a 44-pin J-leaded
PLCC package. In addition to the AD2S80A functions it has a
VCO OUTPUT which is a measure of position within a LSB,
and a COMPLEMENT Data Output.
The AD2S81A is a low cost, monolithic, 12-bit resolver-to
digital converter in a 28-pin ceramic DIP package.
C1437–24–1/91
APPLICATIONS
Control Transformer
ORDERING GUIDE
Model
Operating
Temperature
Range
Accuracy
Package
Option*
AD2S80AJD
AD2S80AKD
AD2S80ALD
AD2S80AAD
AD2S80ABD
AD2S80ASD
AD2S80ATD
AD2S80AUD
AD2S80ASE
AD2S80ATE
AD2S80AUE
AD2S80ASD/883B
AD2S80ATD/883B
AD2S80ASE/883B
AD2S80ATE/883B
0°C to +70°C
0°C to +70°C
0°C to +70°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
–55°C to +125°C
8 arc min
4 arc min
2 arc min
8 arc min
4 arc min
8 arc min
4 arc min
2 arc min
8 arc min
4 arc min
2 arc min
8 arc min
4 arc min
8 arc min
4 arc min
D-40
D-40
D-40
D-40
D-40
D-40
D-40
D-40
E-40A
E-40A
E-40A
D-40
D-40
E-40A
E-40A
*D = Ceramic DIP Package; E = Leadless Ceramic Chip Carrier Package.
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
44-Terminal LCC (E) Package
PRINTED IN U.S.A.
40-Pin Ceramic DIP (D) Package
–16–
REV. A
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