rdc19220 ETC-unknow, rdc19220 Datasheet - Page 14

• Manufacturer Part Number: rdc19220
• Description: 16-bit Monolithic Tracking Resolver Lvdt -to-digital Converters
• Manufacturer: ETC-unknow

Data Device Corporation
www.ddc-web.com
the signal and the reference to reduce the effects of the quadra-
ture. This should be used for greater than 6° phase shift between
Ref and COS/SIN inputs.
LVDT MODE
As shown in TABLE 1 the RDC-19220 Series units can be made
to operate as LVDT-to-digital converters by connecting
Resolution Control inputs A and B to “0,” “1,” or the -5 volt supply.
In this mode the RDC-19220 Series functions as a ratiometric
tracking linear converter. When linear ac inputs are applied from
a LVDT the converter operates over one quarter of its range. This
results in two less bits of resolution for LVDT mode than are pro-
vided in resolver mode.
FIGURE 12B shows a direct LVDT 2 Vrms full scale input. Some
LDVT output signals will need to be scaled to be compatible with
the converter input. FIGURE 12C is a schematic of an input scal-
ing circuit applicable to 3-wire LVDTs. The value of the scaling
constant “a” is selected to provide an input of 2 Vrms at full stroke
REF IN
C
1
= C
2
FIGURE 12A. 2-WIRE LVDT DIRECT INPUT
FIGURE 12B. 3-WIRE LVDT DIRECT INPUT
, set for phase lag = phase lead through the LVDT.
2 WIRE LVDT
R
R
R
R
C
2
aR
bR
+S
A GND
-REF
+REF
+C
-
+
C
aR
bR
1
-
+
FS = 2 V
2 V
-S
-C
2R
2R
RDC-19220
R
R
SIN
COS
R
R
SIN
-S
+S
COS
-C
+C
+REF
-REF
14
REF
of the LVDT. The value of scaling constant “b” is selected to pro-
vide an input of 1 Vrms at null of the LVDT. Suggested compo-
nents for implementing the input scaling circuit are a quad op-
amp, such as a 4741 type, and precision film resistors of 0.1%
tolerance. FIGURE 12A illustrates a 2-wire LVDT configuration.
Data output of the RDC-19220 Series is Binary Coded in LVDT
mode. The most negative stroke of the LVDT is represented by
all zeros and the most positive stroke of the LVDT is represent-
ed by all ones. The most significant 2 bits (2 MSBs) may be used
Note: TABLE 7 refers to FIGURE 12C.
+FS
Notes;
1. R 10kΩ
2. Consideration for the value of R is LVDT loading.
3. RMS values given.
4. Use the absolute values of Va and Vb when subtracting per the formula for calculating
5. See the RDC application manual for calculation examples.
6. Negative voltages are 180˚ phase for the reference.
resistance values, and then use the calculated sign of "Va and Vb" for calculating SIN
and COS. The calculations shown are based upon full scale travel being to the Va side
of the LVDT.
TABLE 7. LVDT OUTPUT CODE (14-BIT R/D OR
FIGURE 12C. 3-WIRE LVDT SCALING CIRCUIT
OUTPUT
+ full travel -1 LSB
V
V
LVDT OUTPUT
+ over full travel
LVDT
B
A
- over full travel
NULL
+0.5 travel
- full travel
-0.5 travel
- 1 LSB
+1 LSB
null
-FS
V
V
A
B
R/2
R
R
R
R
12-BIT LVDT)
COS=-1V -
SIN=-1V+
b =
a =
(V - V )
V
1
aR
bR
Anull
A
RANGE
OVER
2
01
00
00
00
00
00
00
00
11
a
2
-
+
=
B
aR
a
2
bR
-
+
(V - V )
max.
1
V
(V - V )
A
Bnull
A
1111
1100
1000
1000
0111
0100
0000
xxxx
xxxx
B
MSB
B
FS=2V
-2V
RDC-19220 SERIES
2R'
-FS
xxxx
1111
0000
0000
0000
1111
0000
0000
xxxx
2R'
DATA
RDC-19220
INPUT
R'
R'
NULL
R-12/05-0
R'
2V
1V
xxxx
1111
0000
0001
0000
1111
0000
0000
xxxx
R'
LSB
+FS
SIN
COS
SIN
-S
+S
COS
-C
+C
+REF
-REF