L64704 LSI Logic Corporation, L64704 Datasheet - Page 205

• Manufacturer Part Number: L64704
• Description: Satellite Decoder Technical Manual 5/97
• Manufacturer: LSI Logic Corporation

B.3.4
Low Data Rates
When the system functions at low baud rates (generally below 5 Mbaud),
connect the Phase Error Detector outputs to an external DAC, and feed
the voltage level from the output of the DAC to one of the loop filters as
shown in
The lower two bits of the Phase Error Detector outputs are brought out
on the CAR_PED0 and CAR_PED1 pins. The upper four bits of the
Phase detector output are shared with the four CAR_VCO pins as shown
in
Table B.8
CAR_PED Output
Pins
Output Pin Name
CAR_PED0
CAR_PED1
CAR_VCO1P
CAR_VCO2P
CAR_VCO1N
CAR_VCO2N
To enable the Phase Error Detector outputs, set the CAR_PED_SEL bit
in the Carrier Loop Configuration register (Group 4, APR 33) to 1.
1. Choose CAR_KD.
2. Choose .
3. Choose
4. Calculate R
QPSK Demodulator Configuration Example
Table
where ADR is one side of the DAC range. For example, if the DAC
output range is 1 volt, then ADR = 1.
------------------------------- -
2 N
=
–
2 b
B.8:
R
------------------- -
Figure
2
1 +
2
C
2
n.
n
2
5.10.
, R
,
--- -
T
1
1
CAR_PED0
CAR_PED1
CAR_VCO1P
CAR_VCO2P
CAR_VCO1N
CAR_VCO2N
n
, and C from the following equations:
=
min
CAR_OUT_SEL Bit
0
K
---------------------------------------------------------------------------- -
------------ -
1 +
2 b
D
K
1
carvco
f
------------
max
N
R
CAR_PED0
CAR_PED1
CAR_PED2
CAR_PED3
CAR_PED4
CAR_PED5
1
C
CAR_KD ADR
.
1
8192
B-17