DSC-644
14-BIT D/S AND D/R CONVERTER
LOW-PROFILE INDUSTRY STANDARD
FEATURES
DESCRIPTION
The DSC-644 is a low-profile Digital-
to-Synchro (D/S) and Digital-to-
Resolver (D/R) converter. It is only
0.52 inches high. The DSC-644 has a
standard pin configuration and has a
rugged design. The power output
stage has overload and transient pro-
tection, and a thermal cut-off to pre-
vent overheating. The output has
short-circuit protection and an alu-
minum top plate to improve thermal
dissipation. The DSC-644 also has a
circuit design that provides a more
accurate output with an improved
transient response and a negligible
scale factor variation. Reliability has
also been increased.
The DSC-644 module contains an
input reference isolation transformer.
An internal output transformer is also
included for all 400 Hz versions. The
60 Hz option requires a separate out-
put transformer.
•
1.5 VA Drive Capability
•
Protected Output:
Rugged Current-Limited Output
Short-Circuit Protection
Overvoltage Transient Protection
Thermal Cutoff
APPLICATIONS
The DSC-644 can be used when digi-
tized shaft angle data must be convert-
ed to synchro or resolver form to drive
control transformers control differential
transmitters and angle indicators.
Because these converters are very
rugged and meet the requirements of
MIL-STD-202E, they are suitable for
the most severe industrial and military
applications, including military ground
support and avionics. They are ideal for
computer-based systems where digital
information is processed, such as sim-
ulators, flight trainers flight instrumenta-
tion, and fire control systems.
•
Metal Heatsink at Top of Case:
Conservative Thermal Design
•
Very Low Scale Factor Variation:
0.05% Typical
•
Output:
Internal 400 Hz Isolation
Transformer
All Common Synchro/Resolver
Voltage Levels and Frequencies
•
Digital Input:
CMOS and TTL Compatible
Parallel Binary Angle Input
REF
INPUT
RH
RL
REFERENCE
ISOLATION
TRANS-
FORMER
DIGITAL-TO-RESOLVER
CONVERTER
(HIGH ACCURACY:
LOW SCALE FACTOR
VARIATION)
OUTPUT
POWER
AMPLIFIERS
SIN
(S)
COS
(C)
OUTPUT
TRANSFORMER
*
SYNCHRO
OR
RESOLVER
OUTPUT
DIGITAL
ANGLE
INPUT
BIT 1
BIT 14
*
OUTPUT TRANSFORMER IS INTERNAL
FOR 400 Hz. A SEPERATE TRANSFORMER
IS NEEDED FOR 60 Hz.
FIGURE 1. DSC-644 BLOCK DIAGRAM
© 1999 Data Device Corporation
*Patented
TABLE 1. DSC-644 SPECIFICATIONS
Applies over operating temperatures and frequency ranges, ±5% variation
of power supplies. ±10% reference amplitude variation, up to 10% refer-
ence harmonic distortion, and for any balanced load up to full load.
PARAMETER
RESOLUTION
ACCURACY (TO FULL LOAD)
Output Accuracy
Differential Linearity
DIGITAL INPUT
Logic Type
14 bits
±4 minutes
±1 LSB max
Natural binary angle.
parallel positive logic
TTL compatible
Transient protected CMOS
33 kΩ pull-up to +5 V
0.13 Std TTL loads
Reference
Max. Ref.
Voltage Level*
Current
115V rms
0.6 mA
26V rms
0.6 mA
* +20% absolute max. to avoid damage.
VALUE
INTRODUCTION
The DSC-644 (see FIGURE 1) contains an internal digital-to-
resolver (D/R) converter which has an inherently high accuracy
and low scale factor variation. The circuit in the internal D/R con-
verter is based on an algorithm whose theoretical math error is
is only
±
3.5 arc-seconds (less than 5% of 1 LSB), and whose the-
oretical scale factor variation with angle is less than
±
0.015%.
The output is well behaved, with negligible glitches at major tran-
sition points. The accuracy and scale factor error are now limit-
ed by the physical components, not by the algorithm.
The digital imputs are transient protected CMOS switches with
33 k
Ω
pull up resistors to the +5V supply, and can be driven by
all standard TTL gates. If the TTL gates drive other loads as well,
the circuit must allow the 33 k
Ω
resistors to pull up the logic level
to within 1.0V of the +5V supply. Bit weights for the 14 binary
inputs are given in the bit weight table. Angle is determined by
adding bits in the logic 1 state.
TABLE 2. BIT WEIGHT TABLE
BIT
1 MSB
2
3
4
5
6
7
8
9
10
11
12
13
14 LSB
DEG/BIT
180
90
45
22.5
11.25
5.625
2.813
1.406
0.7031
0.3516
0.1758
0.0879
0.0439
0.0220
MIN/BIT
10,800
5,400
2,700
1,350
675
337.5
168.75
84.38
42.19
21.09
10.55
5.27
2.64
1.32
Loading
REFERENCE INPUT
(TRANSFORMER-ISOLATED)
Units with 90 Vrms L-L output
Units with 11.8 Vrms L-L output
ANALOG OUTPUT
(TRANSFORMER-ISOLATED)
Drive Capability (L-L Balanced*)
Synchro Output
90V rms L-L, 360-440 Hz
(Option H)
90V rms L-L, 57-440 Hz
(Option 6)
11.8V rms L-L, 360-440 Hz
(Option L)
Resolver Output
11.8 rms L-L, 360-440 Hz
(Option L)
Output Scale Factor
Absolute (All Causes)
4 kΩ min
4 kΩ min
70
Ω
min
93
Ω
min
±2% max simultaneous amplitude
variation on all output lines, includ-
ing variation with digital angle.
Output amplitude tracks reference
input amplitude.
Variation With Digital Angle
±0.1% max
Output Quadrature
±0.3% max
* The output amplifiers will drive loads
with any phase angle from -90° to +90°
POWER SUPPLY
Voltage
Max Voltage Without Damage
Average Current
Peak Current with Normal Load
Peak Current at Power Turn-on
or Short Circuit
+15V
-15V
+5 V
+18V
-18V
+7 V
150 mA max 150 mA max 5 mA max
330 mA max 330 mA max 5 mA max
600 mA max 600 mA max 5 mA max
The internal reference input transformer provides isolation at
both 60 Hz and 400 Hz, so a change of frequency will not cause
damage. The input is specified for operation at a reference level
of either 115V or 26V rms. The output signals are proportional to
the applied reference, and any distortion in the reference input
will appear in the output signals.
A thermal cutout disables the output power amplifiers when the
internal temperature reaches 125°C. The output is automatically
restored when the temperature drops again.
The DSC-644 will not be damaged by any sequencing order or
interruptions in either the dc supplies or the reference input.
However, if one of the dc supplies is shut down or subsequently
powered up, maximum turn on current (450mA) will be drawn
from the other 15V supply until the missing 15V supply is
restored.
The 60 Hz synchro unit requires both a converter module (DSC-
644-6) and a separate tansformer because of the transformer
size. The output power amplifiers on the -6 module provide a 7V
rms nominal ±2% resolver signal for the external transformer
when the reference input is 115V rms.
TEMPERATURE RANGES
Operating (Temperature Of Metal
Plate On Top Of Case
-1 Option
-55°C to +85°C
-3 Option
0°C to +70°C
Storage
-55°C to +125°C
PHYSICAL CHARACTERISTICS
Converter Module (encapsulated)
Size
3.125 x 2.625 x 0.52 inch
(7.94 x 6.67 x 1.32 cm)
Weight
5.1 oz max (145 g)
60Hz Transformer Module
(encapsulated)
Size
2.25 x 2.25 x 0.81 inch
(5.7 x 5.7 x 2.1 cm)
Weight
10.5 oz max (298 g)
2
Minimum load impedances are listed in the Specifications Table
under Drive Capabilty. The DSC-644 can drive these imped-
ances under the worst case conditions stated in the table. The
minimum load impedances correspond to a 1.5VA drive capabil-
ity when the line voltages and frequencies are at their nominal
values. The metal top of the converter module should be provid-
ed with sufficient air circulation.
DDC also manufactures the DSC-544, another D/S converter
which provides 60 and 400 Hz 90V L-L synchro output. The
DSC-544 is a high efficiency, reference powered converter with
a standard 0.82 inch high profile. It does not require ±15V power
supplies. When driving the same load, the DSC-544 dissipates
half as much power as the DSC-644. At 400 Hz the DSC-544
can drive 4.5VA compared to 1.5VA for the DSC-644. Both units
can drive 1.5VA at 60 Hz, but the DSC-544 does not require an
external transformer at this frequency.
The output amplitudes simultaneously track reference voltage
fluctuations because they are proportional to RH-RL. The ampli-
tude factor A
0
is 90/115V for 90 Vrms L-L output and 11.8/26 for
11.8 Vrms L-L output. The maximum variation in A
0
from all
causes is ±1.9%. The term A (θ) represents the variation of the
amplitude with the digital input angle. A(θ), which is called the
scale factor variation, is a smooth function of
θ
without disconti-
nuities and is less than ±0.001 for all values of
θ.
The total max-
imum variation in A
0
(1 + A(θ)) is therefore ±2%. Because Aθ is
so small, the DSC-644 can be used to drive systems such as X-
Y plotters or CRT displays in which the sin and cos outputs are
used independently (not ratiometrically as in a control trans-
former).
DRIVING CT LOADS
When driving CT loads the DSC-644 must have enough power
drive capability to drive the Z
so
of the load. Z
so
(stator impedance
with rotor open-circuited) is measured as shown in FIGURE 3.
TABLE 3 shows the load impedance of some typical control
transformers.
OUTPUT PHASING AND SCALE FACTOR
The analog output signals have phasing as shown in FIGURES
2A and 2B.
+V
S1-S3 = V
MAX
MAX
SINθ
S3
In Phase with
RH-RL of Converter
2/3 Zso
0
360
30
90
150
210
270
330
θ
CCW
(DEGREES)
Zso = R + jXL
2/3 Zso
S3-S2 = V
S2-S1 = V
SIN(θ
+ 120°)
2/3 Zso
-V
MAX
MAX
S1
S2
MAX
SIN(θ
+ 240°)
FIGURE 2A. SYNCHRO OUTPUT SIGNALS
COS
θ
S2 - S4 = V
MAX
MAX
FIGURE 3. Z
SO
MEASUREMENT
+V
TABLE 3. TYPICAL CONTROL TRANSFORMERS
AND THEIR LOAD IMPEDANCES
θ
CCW
(DEGREES)
IN PHASE
WITH RH-RL
MILITARY
PART NUMBER
26V 08CT4c
26V 11CT4d
11CT4e
15CT4c
15CT6b
18CT4c
18CT6b
23CT4a
23CT6a
SIZE
08
11
11
15
15
18
18
23
23
ZSO
100
21
838
1600
1170
1420
1680
1460
1250
+
+
+
+
+
+
+
+
+
j490
j132
j4955
j9300
j6780
j13260
j5040
j11050
j3980
0
30 60
120150 210 240
300 330 360
-V
MAX
S1-S3 = -V
SIN
θ
MAX
RESOLVER OUTPUT SIGNALS
Resolver output
S1 - S3 = -(RH-RL) A (1+ A(θ
))
sin
θ
0
S2 - S4 = (RH-RL) A (1+ A(θ
))
cos
θ
0
FIGURE 2B. RESOLVER OUTPUT SIGNALS
3
Control transformers are highly inductive loads and it is possible
to save power by tuning such loads. Three capacitors may be
placed across the legs of the synchro stator in a delta configura-
tion:
ACCURACY TESTS
The accuracy of the DSC-644 may be tested with a high accura-
cy synchro/resolver angle indicator and a load such as a control
transformer, as shown in FIGURE 5. The bit switches are set to
the desired test angles and the output angle is measured under
load. The accuracy should conform to the specifications.
S3
TEST METHODS
C
C
S1
C
S2
The DSC-644 converter modules are high-quality products.
These modules were designed to meet the specific test methods
and conditions of MIL-STD-202E (see TABLE 4) unless alterna-
tive methods are specified by the customer in his procurement
documentation.
TABLE 4. MIL-STD-202E TEST METHODS
FIGURE 4. DELTA TUNING CONFIGURATION
The correct value of the capacitance in Farads is given by:
X
C=
L
2
2
4πf (R + X
L
)
where f is the carrier frequency and R and X
L
are the series real
and reactive components of Z
so
. High grade capacitors must be
used and they must be able to withstand the full AC output volt-
age.
When the load has been tuned more loads can be driven in par-
allel, because the load impedance is increased to:
Z=
R + X
L
R
2
2
METHOD
204C
213B
106D*
107D
101D
105C
CONDITION
C
A
--
A
B
B
COMMENT
10G, 2000 Hz vibration
50G, 11 ms shock
Moisture
Thermal shock
Salt spray
50,000 ft, altitude
* when conformally coated on P.C. board
PRINTED CIRCUIT BOARD MOUNTING
When mounting a converter on a printed circuit board, it is very
important to keep logic level signals as far away from the AC and
power signals as possible. Under no circumstances should AC or
power pins be adjacent to data pins at the connector. It is also
prudent to keep the AC and power pins separated from each
other. The intent is to make it impossible to short circuit logic
inputs/outputs to AC or power pins with scope probes, etc.
It is strongly recommended that circuit layouts be designed in
such a way that plated through-holes are not required when
mounting hybrid or discrete modules. If all lands connecting to
pins are located on the opposite (DIP) side of the PC board from
the module, there will be no risk of destroying a pin connection
by ripping out the plated through-hole connection if the module
has to be removed. It will also be much easier to unsolder a mod-
ule without damaging it.
REFERENCE
SYNCHRO OR
RESOLVER
SIGNALS
MSB
BIT 1
DSC-644
BIT 14
S/R ANGLE
INDICATOR
AP-30711
LSB
CT LOAD
FIGURE 5. ACCURACY TEST CIRCUIT
4
2.3 MAX
2.0
.040±.0020 DIA
(TYP) x .2 MIN
.15 MAX (TYP)
.82 MAX
SILVER
DOT
NEAR PIN 1
3.80±.06
.30 ± .03 typ.
NON-CUMULATIVE
1 2 3 4 5 6 7 8 9 10 1112
TRANSFORMER
PART NUMBER 3932
TOP VIEW
6.32 NC-2B X 1/4 MIN BRASS
INSERTS (4 ON EACH SIDE)
.50 ± .06
4
5
6
7
1
0.7
2
1.0
1.3
2.0
2.3 MAX
3
1.50 MAX
.20 ± .03
.30 MAX
CRES OR BRASS
INSERT 4-40 THRU (2)
BOTTOM (PIN) VIEW
PIN NUMBERS NOT
LABELED ON BOTTOM
1.90
.1.375±.01
MAX
.25 MAX
TERMINAL ENVELOPE
.30 MAX
1
4
+S
2
DDC 25924
6
3
7
RESOLVER
INPUT
7V
-S
+C
-C
5
7
6
3
2
S3
SYNCHRO
OUTPUT
90V L-L
5
4
1
S1
3.813 ± .01
4.40 MAX
SIDE VIEW
Dimensions are in inches.
TRANSFORMER CONNECTIONS
DETAIL OF PIN
S2
PIN NUMBERS MARKED
ON TOP FACE ONLY
TOP VIEW
(Dimensions in inches, ± 0.01 inch,
unless otherwise indicated.)
.096
Transformer
Pin Number
1
2
3
4
5
6
7
8
9
10
11
12
S1
S3
S2
SIN
GND
GND
COS
RH
RL
+R
RC
-R
Connect
To
Synchro Output
90v rms L-L
47-440 Hz
To
Converter
Module
.125
.035
TRANSFORMER CONNECTIONS
Transformer
Pin Number
1
2
3
4
5
6
7
Connect
To
S1
Synchro Output
S3
90v L-L
S2
57-440 Hz
SIN
To
GND
Converter
GND
Module
COS
.071
.187
.125
SIDE VIEW
Do Not Use
PIN CALL-OUTS SHOWN
FOR REFERENCE ONLY.
Do Not Use
*For 50Hz applications P/N DDC-3932 must be ordered.
FIGURE 6. MECHANICAL OUTLINE,
60 HZ EXTERNAL SYNCHRO TRANSFORMER
- DDC-25924
0.26 ±0.01
2.625
±0.015
FIGURE 7. MECHANICAL OUTLINE,
50 HZ EXTERNAL SYNCHRO TRANSFORMER
- DDC-3932*
0.26 ±0.01
2.625
±0.015
14 LSB
13
12
11
10
9
8
7
6
+
+
+
+
.040 Dia
(±.002)
0.52
MAX
14 LSB
13
12
11
10
9
8
7
6
5
4
3
S4
S3
S2
S1
+ 15V
GND
+
+
+
2.60
DSC-644-H
or
DSC-644-L
or
DRC-644-L
DSC-644-6
SIN
COS
+
+15V
GND
+
-15V
+5V
RL
RH
0.2±001
Non Cumulative
2.60
3. 25
1
±0.015
+
-15V
RL
RH
5
4
3
2
1 MSB
2
1 MSB
0.21
±0.01
2.20
±0.10
0.21 ± 0.01
2.20
±0.10
0.25
(Min)
BOTTOM VIEW
BOTTOM VIEW
SIDE VIEW
(H, L, or 6)
Notes:
1. Pin labels on bottom view are for reference only.
2. All dimensions shown are in inches.
3. Pin material meets solderability requirements of MIL-STD-202E,
Method 208C.
4. Case material is glass filled Diallyl Phthalate per MIL-M-14, Type
SDG-F, except top surface is a black anodized aluminum plate for
heat transfer.
5. Pin S4 is present on resolver units only.
6. Any LSB pins not used should be grounded
FIGURE 8. DSC-644 MECHANICAL OUTLINE
5
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