AD9853 Analog Devices, AD9853 Datasheet - Page 14

• Manufacturer Part Number: AD9853
• Description: Programmable Digital OPSK/16-QAM Modulator
• Manufacturer: Analog Devices

AD9853
Figure 32. Basic Implementation of AD9853 Digital Modulator and AD8320 Programmable Cable Driver Amplifier in
Return-Path Application
CONTROL BUS
T
X
DAC OUT
ENABLE
RESET
t
t
NOTE 1. DURING THIS INTERVAL ALL CONTROL BUS REGISTERS MUST BE PROGRAMMED.
NOTE 2. DURING THIS INTERVAL THE CONTROL REGISTER (48h) MAY NEED TO BE REPROGRAMMED DUE TO BEING CLEARED
NOTE 3. THREE RESETS ARE REQUIRED TO ENSURE THAT THE DATA PATH IS ZERO'D.
RL
DL
: MINIMUM RESET LOW TIME = 10ns
: DATA LATENCY = 6 SYMBOLS
BY THE PRECEDING RESET PULSE.
t
RL
NOTES ON THE RESET FUNCTION:
1. RESET IS ACTIVE LOW
2. RESET ZEROS THE CONTROL REGISTER AT ADDRESS 48 HEX WHICH CAUSES THE FOLLOWING DEFAULT
3. SERIAL CONTROL BUS IS RESET AND INITIALIZED.
4. OUTPUTS OF MODULATION ENCODERS ARE SET TO ZERO. THIS ALLOWS THE FIR FILTERS AND
5. THE PREAMBLE IS CLEARED UPON EXECUTION OF THE RESET FUNCTION.
CONDITION TO EXIST:
SUBSEQUENT INTERPOLATION FILTERS TO BE FLUSHED WITH ZEROS AS LONG AS T
A. 6
B. OUTPUT SPECTRUM IS SET TO I COS+Q SIN
C. DIGITAL PLL POWER-DOWN IS DISABLED
D. PLL POWER-DOWN IS DISABLED
E. DAC PLL POWER-DOWN IS DISABLED
REFCLK IS DISABLED
DATA IN
CLOCK IN
NOTE 1
CONTROL
REF
DIRECT
LINES
Figure 31. Recommended Start-Up Sequence
CONTROL PROCESSOR
QPSK/16–QAM
MODULATOR
AD9853
DIGITAL
PROCESSOR
CONTROL
CONTROL
SERIAL
BUS
GAIN CONTROL BUS
CIRCUIT AND
–14–
COUPLING
LP FILTER
NOTE
POWER
DOWN
2
PROGRAMMABLE
CABLE DRIVER
AMPLIFIER
AD8320
NOTE
2
DIPLEXER
X
ENABLE IS HELD LOW.
TO
t
DL
START UP
SEQUENCE
REV. C