
4
Data Device Corporation
www.ddc-web.com
SD-14531
VALUE
Notes:
(1) Pin Programmable.
(2) VEL polarity is negative voltage for positive angular rate.
(3) XX5 ordering option = ±1.3 minutes resolver mode, ±1.6 minutes synchro
mode (16-bit mode only).
TRANSFORMER
CHARACTERISTICS (CONT.)
Minimum Input impedances
(Balanced)
90 V L-L
26 V L-L
11.8 V L-L
60 Hz TRANSFORMERS
Reference Transformer
Carrier Frequency Range
Input Voltage Range
Input Impedance
Input Common-Mode Voltage
Output Description
Output Voltage
Power Required
Signal Transformer
Carrier Frequency Range
Input Voltage Range
Input Impedance
Input Common-Mode Voltage
Output Description
Output Voltage
Power Required
PARAMETER
TABLE 1. SD-14531 SPECIFICATIONS (CONT.)
accuracy of the converter. The control transformer performs the
following trigonometric computation:
sin(
θ - φ) = sinθ cosφ - cosθ sinφ
Where:
θ is angle theta representing the resolver shaft position
φ is digital angle phi contained in the up/down counter
The tracking process consists of continually adjusting
φ to make
(
θ - φ) = 0, so that φ will represent the shaft position θ.
The output of the demodulator is an analog DC level proportion-
al to sin(
θ - φ). The error processor receives its input from the
demodulator and integrates this sin(
θ - φ) error signal which then
drives the VCO. The VCO’s clock pulses are accumulated by the
up/down counter. The velocity voltage accuracy, linearity and off-
set are determined by the quality of the VCO. Functionally, the
up/down counter is an incremental integrator. Therefore, there
are two stages of integration which makes the converter a Type
II tracking servo.
In a Type II servo, the VCO always settles to a counting rate
which makes d
φ/dt equal to dθ/dt without lag. The output data will
always be fresh and available as long as the maximum tracking
rate of the converter is not exceeded.
The reference conditioner is a comparator that produces the
square wave reference voltage which drives the demodulator. It’s
single-ended Input Z is 250k Ohms min, 500k Ohms differential.
SPECIAL FUNCTIONS
The synthesized reference section of the SD-14531 eliminates
errors caused by quadrature voltage. Due to the inductive nature
of synchros and resolvers, their signals typically lead the refer-
ence signal (RH and RL) by about 6°. When an uncompensated
reference signal is used to demodulate the control transformer’s
output, quadrature voltages are not completely eliminated. In a
14-bit converter it is not necessary to compensate for the refer-
ence signal’s phase shift. A 6° phase shift will, however, cause
problems for the one minute accuracy converters. As shown in
FIGURE 1, the converter synthesizes its own cos(
ωt + α) refer-
ence signal from the sin
θ - cos(ωt + α), cosθ - cos(ωt + α) signal
inputs and from the cos
ωt reference input. The phase angle of
reference input is used to choose between the +180° and -180°
phases. The synthesized reference will always be exactly in
phase with the signal input, and quadrature errors will therefore
be eliminated. The synthesized reference circuit also eliminates
the 180° false error null hangup.
Quadrature voltages in a resolver or synchro are by definition the
resulting 90° fundamental signal in the nulled out error voltage
THEORY OF OPERATION
The SD-14531 Series are small, 36-pin DDIP synchro-to-digital
hybrid converters. As shown in the block diagram (FIGURE 1),
the SD-14531 can be broken down into the following functional
parts: Signal Input Option, Converter, Analog Conditioner, Power
Supply Conditioner, and Digital Interface.
CONVERTER OPERATION
As shown in FIGURE 1, the converter section of the SD-14531
contains a high accuracy control transformer, demodulator, error
processor, voltage-controlled oscillator (VCO), up-down counter,
and reference conditioner. The converter produces a digital
angle which tracks the analog input angle to within the specified
SynchroZIN(ZSO)
ResolverZIN
180
100 k
-
30 k
20 k
30 k
47 - 440 Hz
80 -138 V rms; 115 V rms
nominal resistive
600 k
min, resistive
500 V rms transformer isolated
+R (in phase with RH-RL) and -R
(in phase with RL- RH) derived
from op-amps. Short-Circuit proof.
3.0 V nominal riding on ground
reference V. Output Voltage level
tracks input level.
4 mA typ, 7 mA max from +15 V
supply.
47 - 440 Hz
10 -100 V rms L- L; 90 V rms
L- L nominal
148 k
min L- L balanced
resistive
±500 V rms, transformer isolated
Resolver output,
- Sine (- S) + Cosine (+C) derived
from op-amps. Short circuit proof.
1.0 V rms nominal riding on
ground reference V. Output volt-
age level tracks input level.
4 mA typ, 7 mA max from +15 V
supply.