RDC-19220 SERIES
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®
16-BIT MONOLITHIC TRACKING RESOLVER
(LVDT)-TO-DIGITAL CONVERTERS
FEATURES
•
+5 Volt Only Option
•
Only Five External Passive
Components
•
Programmable:
- Resolution: 10-, 12-, 14-, or 16-Bit
- Bandwidth: to 1200 Hz
- Tracking: to 2300 RPS
•
Differential Resolver and LVDT
Input Modes
•
Velocity Output Eliminates
Tachometer
•
Built-In-Test (BIT) Output,
No 180° Hangup
DESCRIPTION
The RDC-19220 Series of converters are low-cost, versatile, 16-bit
monolithic, state-of-the-art Resolver(/LVDT)-to-Digital Converters.
These single-chip converters are available in small 40-pin DDIP, or 44-
pin J-Lead packages and offer programmable features such as reso-
lution, bandwidth and velocity output scaling.
Resolution programming allows selection of 10-, 12-, 14-, or 16-bit,
with accuracies to 2.3 min. This feature combines the high tracking
rate of a 10-bit converter with the precision and low-speed velocity
resolution of a 16-bit converter in one package.
The velocity output (VEL) from the RDC-19220 Series, which can be
used to replace a tachometer, is a 4 V signal (3.5 V with the +5 V only
option) referenced to ground with a linearity of 0.75% of output volt-
age. The full scale value of VEL is set by the user with a single resis-
tor.
RDC-19220 Series converters are available with operating tempera-
ture ranges of 0° to +70°C, -40° to +85°C and -55° to +125°C. Military
processing is available (consult factory).
•
Small Size: 40-Pin DDIP or
44-Pin J-Lead Package
•
-55° to +125°C Operating
Temperature Available
APPLICATIONS
With its low cost, small size, high accuracy and versatile performance,
the RDC-19220 Series converter is ideal for use in modern high-per-
formance industrial and military control systems. Typical applications
include motor control, radar antenna positioning, machine tool con-
trol, robotics, and process control.
FOR MORE INFORMATION CONTACT:
Data Device Corporation
105 Wilbur Place
Bohemia, New York 11716
631-567-5600 Fax: 631-567-7358
www.ddc-web.com
Technical Support:
1-800-DDC-5757 ext. 7382
©
1999 Data Device Corporation
Data Device Corporation
www.ddc-web.com
+REF -REF
BIT
-VSUM
SIN
-S
+S
COS
-C
+C
-
+
A B
+5C
+CAP
-CAP
-5C
A GND
+5 V
GND
-5 V
-5 V
INVERTER
16 BIT
UP/DOWN
COUNTER
E
DATA
LATCH
VCO
&
TIMING
-VCO
R
S
HYSTERESIS
INTEGRATOR
R
V
-
+
CONTROL
TRANSFORMER
GAIN
DEMODULATOR
R
1
C
BW
C
BW
10
R
B
VEL
2
RDC-19220 SERIES
L-11/02-300
R
C
INH
EM BIT 1 EL
THRU
BIT 16
A
B
CB
FIGURE 1. RDC-19220 SERIES BLOCK DIAGRAM
TABLE 1. RDC-19220 SPECIFICATIONS
These specifications apply over the rated power supply, temperature
and reference frequency ranges, and 10% signal amplitude variation
and harmonic distortion.
PARAMETER
RESOLUTION
ACCURACY
REPEATABILITY
DIFFERENTIAL LINEARITY
REFERENCE
Type
Voltage:
differential
single ended
overload
Frequency
Input Impedance
SIGNAL INPUT
Type
Voltage: operating
overload
Input impedance
DIGITAL INPUT/OUTPUT
Logic Type
Inputs
UNIT
Bits
Min
LSB
LSB
VALUE
10, 12, 14, or 16
4 or 2 + 1 LSB (note 3)
1 max
1 max in the 16th bit
(+REF, -REF)
Differential
V
P
-
P
V
P
V
Hz
Ohm
±10 max
±5 max
±25 continuous, 100 transient
DC to 40,000 (note 4)
10M min // 20 pf
TABLE 1. RDC-19220 SPECIFICATIONS (CONTD)
PARAMETER
DYNAMIC
CHARACTERISTICS
Resolution
Tracking Rate (max)(note 4)
Bandwidth(Closed Loop)
(max) (note 4)
Ka
A1
A2
A
B
Acceleration (1 LSB lag)
Settling Time(179° step)
VELOCITY
CHARACTERISTICS
Polarity
Voltage Range(Full Scale)
Scale Factor Error
Scale Factor TC
Reversal Error
Linearity
Zero Offset
Zero Offset TC
Load
Noise
POWER SUPPLIES
Nominal Voltage
Voltage Range
Max Volt. w/o Damage
Current
TEMPERATURE RANGE
Operating
-30X
-20X
-10X
Storage
plastic package
ceramic package
THERMAL RESISTANCE
Junction-to-Case (θjc)
40-pin DDIP (plastic)
40-pin DDIP (ceramic)
44-pin J-Lead (plastic)
44-pin J-Lead (ceramic)
PHYSICAL
CHARACTERISTICS
Size: 40-pin DDIP
44-pin J-Lead
Weight:
40-pin DDIP
44-pin J-Lead
Notes:
UNIT
VALUE
(at maximum bandwidth)
bits
rps
Hz
1/sec
2
1/sec
1/sec
1/sec
1/sec
deg/s
2
msec
10
1152
1200
5.7M
19.5
295k
2400
1200
2M
2
12
288
1200
5.7M
19.5
295k
2400
1200
500k
8
14
72
600
1.4M
4.9
295k
1200
600
30k
20
16
18
300
360k
1.2
295k
600
300
2k
50
(+S, -S, SIN, +C, -C, COS)
Resolver, differential, groundbased
Vrms 2 ±15%
V
±25 continuous
Ohm 10M min//10 pf.
TTL/CMOS compatible
Logic 0 = 0.8 V max.
Logic 1 = 2.0 V min.
Loading =10 µA max P.U. current
source to +5 V //5 pF max.
CMOS transient protected
Logic 0 inhibits; Data stable
within 0.3 µs
Logic 0 enables; Data stable
within 150 ns
Logic 1 = High Impedance
Data High Z within 100 nS
Mode B
resolver 0
"
0
"
1
"
1
LVDT -5 V
"
0
"
1
"
-5 V
A Resolution
0
10 bits
1
12 bits
0
14 bits
1
16 bits
0
8 bits
-5 V
10 bits
-5 V
12 bits
-5 V
14 bits
V
%
PPM/C
%
%
mv
µV/C
kΩ
(Vp/V)%
V
%
V
mA
Positive for increasing angle
±4 (at nominal ps)
10 typ
20 max
100 typ
200 max
0.75 typ 1.3 max
0.25 typ 0.50 max
5 typ
10 max
15 typ
30max
8 max
1 typ
.125 min 2 max
(note 5)
+5
-5
± 5 +5, -20 (-4 V to -5.25 V)
+7
-7
14 typ, 22 max (each)
Inhibit (INH)
Enable Bits 1 to 8 (EM)
Enable Bits 9 to 16 (EL)
Resolution and Mode
Control (A & B)
(see notes 1 and 2.)
°C
°C
°C
°C
°C
0 to +70
-40 to +85
-55 to +125
-65 to +150
-65 to +150
Outputs
Parallel Data (1-16)
°C/W
°C/W
°C/W
°C/W
92.4
4.6
72.6
2.4
Converter Busy (CB)
Zero Index
(Zl)
Built-in-Test (BIT)
Drive Capability
10, 12, 14, or 16 parallel lines;
natural binary angle positive
logic (see TABLE 2)
0.25 to 0.75 µs positive pulse
leading edge initiates counter
update.
Logic 1 at all 0s (ENL to -5 V);
LSBs are enabled
Logic 0 for BIT condition.
±100 LSBs of error typ. with a
filter of 500 µS, or total Loss-of-
Signal (LOS)
50 pF +
Logic 0; 1 TTL load, 1.6 mA at
0.4 V max
Logic 1; 10 TTL loads, -0.4 mA
at 2.8 V min
Logic 0; 100 mV max driving CMOS
Logic 1; +5 V supply minus 100mV
min driving CMOS, High Z;
10 uA//5 pF max
in(mm) 2.0 x 0.6 x 0.2 (50.8 x 15.24 x 5.08)
in(mm) 0.690 square (17.526)
oz(g)
oz(g)
Plastic
0.21 (5.95)
0.08 (2.27)
Ceramic
0.24 (6.80)
0.065 (1.84)
1. Unused data bits are set to logic “0.”
2. In LVDT mode, bit 16 is LSB for 14-bit resolution
or bit 12 is LSB for 10-bit resolution.
3. Accuracy in LVDT mode is 0.15% + 1 LSB of full scale.
4. See text, General Setup Considerations and Higher
Tracking Rates.
5. See text: General Setup Considerations for RDC19222.
Data Device Corporation
www.ddc-web.com
3
RDC-19220 SERIES
L-11/02-300
THEORY OF OPERATION
The RDC-19220 Series of converters are single CMOS custom
monolithic chips. They are implemented using the latest IC tech-
nology which merges precision analog circuitry with digital logic
to form a complete, high-performance tracking resolver-to-digital
converter. For user flexibility and convenience, the converter
bandwidth, dynamics and velocity scaling are externally set with
passive components.
FIGURE 1 is the functional block diagram of the RDC-19220
Series. The converter operates with ±5 Vdc power supplies.
Analog signals are referenced to analog ground, which is at
ground potential. The converter is made up of two main sections;
a converter and a digital interface. The converter front-end con-
sists of sine and cosine differential input amplifiers. These inputs
are protected to ±25 V with 2 kΩ resistors and diode clamps to
the ±5 Vdc supplies. These amplifiers feed the high accuracy
Control Transformer (CT). Its other input is the 16-bit digital angle
φ.
Its output is an analog error angle, or difference angle,
between the two inputs. The CT performs the ratiometric trigono-
metric computation of SINθCOSφ - COSθSINφ = SIN(θ-φ) using
amplifiers, switches, logic and capacitors in precision ratios.
Note:
The transfer function of the CT is normally trigonometric,
but in LDVT mode the transfer function is triangular (linear)
and could thereby convert any linear transducer output.
The converter accuracy is limited by the precision of the com-
puting elements in the CT. In these converters, ratioed capacitors
are used in the CT instead of the more conventional precision
ratioed resistors. Capacitors, used as computing elements with
op-amps, need to be sampled to eliminate voltage drifting.
Therefore, the circuits are sampled at a high rate (67 kHz) to
eliminate this drifting and at the same time to cancel out the op-
amp offsets.
The error processing is performed using the industry standard
technique for type II tracking R/D converters. The dc error is inte-
grated yielding a velocity voltage which in turn drives a voltage
controlled oscillator (VCO). This VCO is an incremental integra-
tor (constant voltage input to position rate output) which togeth-
RB C
BW
er with the velocity integrator forms a type II servo feedback loop.
A lead in the frequency response is introduced to stabilize the
loop and another lag at higher frequency is introduced to reduce
the gain and ripple at the carrier frequency and above. The set-
tings of the various error processor gains and break frequencies
are done with external resistors and capacitors so that the con-
verter loop dynamics can be easily controlled by the user.
TABLE 2. DIGITAL ANGLE OUTPUTS
BIT
1(MSB)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
DEG/BIT
180
90
45
22.5
11.25
5.625
2.813
1.405
0.7031
0.3516
0.1758
0.0879
0.0439
0.0220
0.0110
0.0055
MIN/BIT
10800
5400
2700
1350
675
337.5
168.75
84.38
42.19
21.09
10.55
5.27
2.64
1.32
0.66
0.33
Note: EM enables the MSBs and EL enables the LSBs.
TRANSFER FUNCTION AND BODE PLOT
The dynamic performance of the converter can be determined from
its Transfer Function Block Diagrams and its Bode Plots (open and
closed loop). These are shown in FIGURES 2, 3, and 4.
The open loop transfer function is as follows:
A
2
S +1
B
Open Loop Transfer Function =
2
S +1
S
10B
(
(
)
)
where A is the gain coefficient and A
2
= A
1
A
2
and B is the frequency of lead compensation.
VEL
C
BW
/10
RS
-VSUM
VEL
-VCO
50 pf
C
VCO
CT
RESOLVER
INPUT
(θ)
+
GAIN
DEMOD
1
C
S
F
S
11 mV/LSB
±1.25 V
THRESHOLD
R
V
R1
VCO
-
16 BIT
UP/DOWN
COUNTER
H=1
DIGITAL
OUTPUT
(φ)
FIGURE 2. TRANSFER FUNCTION BLOCK DIAGRAM #1
Data Device Corporation
www.ddc-web.com
4
RDC-19220 SERIES
L-11/02-300
The components of gain coefficient are error gradient, integrator
gain and VCO gain. These can be broken down as follows:
- Error Gradient = 0.011 volts per LSB (CT + Error Amp + Demod
with 2 Vrms input)
- Integrator Gain = Cs Fs volts per second per volt
1.1 C
BW
- VCO Gain =
1
LSBs per second per volt
1.25 R
V
C
VCO
4) The BIT output which is active low is activated by an error
of approximately 100 LSBs. During normal operation for step
inputs or on power up, a large error can exist.
5) This device has several high impedance amplifier inputs
(+C, -C, +S, -S, -VCO and -VSUM). These nodes are sensi-
tive to noise and coupling components should be connected
as close as possible.
6) Setup of bandwidth and velocity scaling for the optimized
critically damped case should proceed as follows:
where: Cs = 10 pF
Fs = 67 kHz when Rs = 30 kΩ
Fs = 100 kHz when Rs = 20 kΩ
Fs = 134 kHz when Rs = 15 kΩ
C
VCO
= 50 pF
R
V
, R
B
, and C
BW
are selected by the user to set velocity scaling
and bandwidth.
- Select the desired f
BW
(closed loop) based on overall
system dynamics.
- Select f carrier
≥
3.5f
BW
value,
{
For the converter’s max tracking rate 4.
}
see the row indicated in TABLE
GENERAL SETUP CONSIDERATIONS
DDC has external component selection software which consid-
ers all the criteria below, and in a simple fashion, asks the key
parameters (carrier frequency, resolution, bandwidth, and track-
ing rate) to derive the external component value.
The following recommendations should be considered when
installing the RDC-19220 Series R/D converters:
1) In setting the bandwidth (BW) and Tracking Rate (TR)
(selecting five external components), the system require-
ments need to be considered. For greatest noise immunity,
select the minimum BW and TR the system will allow.
2) Power supplies are ±5 V dc. For lowest noise performance
it is recommended that a 0.1 µF or larger cap be connected
from each supply to ground near the converter package.
3) Resolver inputs and velocity output are referenced to A
GND. This pin should be connected to GND near the con-
verter package. Digital currents flowing through ground will
not disturb the analog signals.
- Compute Rv = 55 kΩ x
Application max. rate
3.2 x Fs (Hz) x 10
8
Rv x (f
BW
)
2
- Compute C
BW
(pF) =
- Where Fs = 67 kHz for R CLK = 30 KΩ
100 kHz for R CLK = 20 KΩ
134 kHz for R CLK = 15 KΩ
- Compute R
B
=
0.9
C
BW
x f
BW
- Compute
C
BW
10
Note: DDC has software available to perform the previous calcu-
lations. Contact DDC to request software or visit our web-
site at www.ddc-web.com to download software.
ERROR PROCESSOR
RESOLVER
INPUT
(θ)
+
-
CT
e
A1 S + 1
B
S
S +1
10B
VELOCITY
OUT
VCO
A
2
S
DIGITAL
POSITION
OUT (φ)
GAIN = 4
2A
OPEN LOOP
B
A
-6
db
/o
-1
2d
ct
b/o
(CRITICALLY DAMPED)
ω
(rad/sec)
10B
ct
(B = A/2)
GAIN = 0.4
H=1
f
BW
= BW (Hz) =
2A
2 2A
2A
π
CLOSED LOOP
ω
(rad/sec)
FIGURE 3. TRANSFER FUNCTION
BLOCK DIAGRAM #2
Data Device Corporation
www.ddc-web.com
5
FIGURE 4. BODE PLOTS
RDC-19220 SERIES
L-11/02-300
Microcontroller MCU
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