AD9856/PCB Analog Devices Inc, AD9856/PCB Datasheet - Page 30

• Manufacturer Part Number: AD9856/PCB
• Description: BOARD EVAL FOR AD9856
• Manufacturer: Analog Devices Inc
• Type: DDS Modulatorsr

Specifications of AD9856/PCB

• Rohs Status: RoHS non-compliant
• For Use With/related Products: AD9856
• Lead Free Status / RoHS Status: Not Compliant

AD9856
PROGRAMMING/WRITING THE AD8320/AD8321
CABLE DRIVER AMPLIFIER GAIN CONTROL
Programming the gain control register of the AD8320/AD8321
programmable cable driver amplifier can be accomplished via
the AD9856 serial port. Four 8-bit registers (one per profile)
within the AD9856 store the gain value to be written to the
AD8320/AD8321. The AD8320/AD8321 is written via three
dedicated AD9856 output pins that are directly connected
to the AD8320/AD8321 serial input port. The transfer of
data from the AD9856 to the AD8320/AD8321 requires
136 SYSCLK clock cycles and occurs upon detection of three
conditions. Each condition is described next.
Power-Up Reset
Upon initial power up, the AD9856 clears (Logic 0) the contents
of control registers 07h, 0Dh, 13h, and 19h, which defines the
lowest gain setting of the AD8320/AD8321. Thus, the AD9856
writes all 0s out of the AD8320/AD8321 serial interface.
CA ENABLE
CA DATA
CA CLK
Figure 50. Programmable Cable Driver Amplifier Output Control Interface Timing
t
t
ES
DS
VALID DATA WORD G1
SYMBOL
t
t
t
t
t
t
DS
DH
WH
CK
ES
EH
8 CLOCK CYCLES
MSB...LSB
t
WH
t
CA DATA SETUP TIME
CA DATA HOLD TIME
CA CLOCK PULSE HIGH
CA CLOCK PERIOD
CA ENABLE SETUP TIME
CA ENABLE HOLD TIME
DEFINITION
CK
Rev. C | Page 30 of 36
t
EH
GAIN TRANSFER
G1
Change in Profile Selection Bits (PS1, PS0)
The AD9856 samples the PS1, PS0 input pins and writes to the
AD8320/ AD8321 gain control register when a change in profile
is determined. The data written to the AD8320/AD8321 comes
from the AD9856 gain control register associated with the
current profile.
Serial Port Write of AD9856 Registers Containing
AD8320/AD8321 Data
The AD9856 writes to the AD8320/AD8321 with data from the
gain control register associated with the current profile
whenever any AD9856 gain control register is updated. The
user does not have to write the AD9856 in any particular order
or to be concerned with time between writes. If the AD9856 is
currently writing to the AD8320/AD8321 while one of the four
AD9856 gain control registers is being addressed, the AD9856
immediately terminates the AD8320/AD8321 write sequence
(without updating the AD8320/AD8321) and begins a new
AD8320/AD8321 write sequence.
VALID DATA WORD G2
GAIN TRANSFER
6.5ns
2ns
9ns
25ns
17ns
2.0ns
MIN
G2