AD9957 Analog Devices, AD9957 Datasheet - Page 12

• Manufacturer Part Number: AD9957
• Description: 1 GSPS Quadrature Digital Upconverter
• Manufacturer: Analog Devices

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DataSheet
AD9957
DATA is shown in Figure 5 and Figure 6.
Input Data Assembler
The input to the AD9957 is an 18-bit parallel data port in quad-
rature modulation mode (or a dual serial data port in the BFI
mode). It is assumed that two consecutive 18-bit words repre-
sent the real (I) and imaginary (Q) parts of a complex number
that has the form I+jQ. The 18-bit words are supplied to the
input of the AD9957 at a rate of:
Where f
lation factor of the programmable interpolation filter.
f
DATA
4
U
=
TxENABLE
SYSCLK
.com
D<13:0>
f
PDCLK
SYSCLK
2
R
is the sample rate of the DAC and R is the interpo-
(QDUC mode)
Figure 5. 18-Bit Parallel Port Timing Diagram—Quadrature Modulation Mode
t
DS
t
DS
Figure 6: Dual Serial I/Q Bitstream Timing Diagram – BFI mode
I
0
t
DH
Symbol
Symbol
t
t
t
t
DH
DH
DS
DS
Q
Table 3. Parallel Data Bus Timing
0
Table 4: Serial Data Bus Timing
Rev. PrF | Page 12 of 38
Data Setup Time
Data Setup Time
Data Hold Time
Data Hold Time
Definition
Definition
I
1
When device is programmed to operate in BFI mode, the 18-bit
parallel input is converted to a dual serial input. That is, one
pin is assigned as the serial input for the "I" words and one pin
is assigned as the serial input for the "Q" words. The other 16
pins are not used in the BFI mode. Furthermore, each I and Q
word has 16-bit resolution (as compared with 18-bit resolution
in the non-BFI mode). In BFI mode, f
and Q data streams and is given by:
Encoding and pulse shaping of symbols must be implemented
before the data is presented to the input of the AD9957. Data
f
DATA
Q
1
=
f
SYSCLK
R
Minimum
Minimum
PRELIMINARY TECHNICAL DATA
TBD
TBD
4 ns
0 ns
(BFI mode)
I
N
t
DH
DATA
is the bit rate of the I
Q
N