AD2S80A
REV. B
–6–
CONNECTING THE CONVERTER
The power supply voltages connected to +V
S
and –V
S
pins
should be +12 V dc and –12 V dc and must not be reversed.
The voltage applied to V
L
can be 5 V dc to +V
S
.
It is recommended that the decoupling capacitors are connected
in parallel between the power lines +V
S
, –V
S
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 +V
L
and
DIGITAL GROUND adjacent to the converter.
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 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 indi-
vidually screened twisted pair cables with the sine, cosine and
reference signals twisted separately.
SIGNAL GROUND and ANALOG GROUND are connected
internally. ANALOG GROUND and DIGITAL GROUND
must be connected externally.
The external components required should be connected as
shown in Figure 1.
CONVERTER RESOLUTION
Two major areas of the AD2S80A specification can be selected
by the user to optimize the total system performance. The reso-
lution 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.
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.
Note: When changing resolution under dynamic conditions, do
it when the BUSY is low, i.e., when Data is not changing.
A1
A2
SEGMENT
SWITCHING
R-2R DAC
A3
OUTPUT DATA LATCH
PHASE
SENSITIVE
DETECTOR
DEMOD
I/P
DEMOD
O/P
INTEGRATOR
O/P
AD2S80A
C2
HF FILTER
R1
C1
C3
R3
VCO + DATA
TRANSFER LOGIC
R4
INTEGRATOR
I/P
R9
R8
–12V+12V
OFFSET ADJUST
C4
C5
R5
AC ERROR O/P
REFERENCE
I/P
BANDWIDTH
SELECTION
R6
R7
C6
TRACKING
RATE
SELECTION
VELOCITY
SIGNAL
VCO
I/P
SC1 SC2DATA
LOAD
16-BIT UP/DOWN COUNTER
ENABLE
16 DATA BITS
BYTE
SELECT
5V
DIG
GND
BUSY DIRN
INHIBIT
SIN
SIG GND
COS
GND
RIPPLE
CLK
+12V
–12V
R2
Figure 1. AD2S80A Connection Diagram
