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AD9115BCPZRL7 View Datasheet(PDF) - Analog Devices

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AD9115BCPZRL7 Datasheet PDF : 52 Pages
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Data Sheet
AD9114/AD9115/AD9116/AD9117
DB[n:0]
(INPUT)
OR
D-FF
0
D-FF
1
DCLKIO-INT
D-FF
2
D-FF
3
RETIMER-CLK
D-FF
4
D-FF
TO DAC CORE 5
IOUT
CLKIN-INT
IOUT
NOTES
D-FFs:
0: RISING OR FALLING EDGE
TRIGGERED FOR I OR Q DATA.
1, 2, 3, 4: RISING EDGE TRIGGERED.
IE
IE
DELAY2
DCLKIO
(INPUT/OUTPUT)
OE
CLKIN
(INPUT)
Figure 94. Simplified Diagram of AD9114/AD9115/AD9116/AD9117 Timing
DIGITAL DATA LATCHING AND RETIMER SECTION
The AD9114/AD9115/AD9116/AD9117 have two clock inputs,
DCLKIO and CLKIN. The CLKIN is the analog clock whose
jitter affects DAC performance, and the DCLKIO is a digital clock
from an FPGA that needs to have a fixed relationship with the
input data to ensure that the data is sampled correctly by the
flip-flops on the pads.
Setting Bit 1 or Bit 0 of SPI Address 0x02, DCOSGL or DCODBL,
to logic high allows the user to get a DCLKIO output from the
CLKIN input for use in the user’s PCB system.
It is strongly recommended that DCI_EN = DCOSGL = high,
or DCI_EN = DCODBL = high not be used, even though the
device may appear to function correctly. Similarly, DCOSGL
and DCODBL should not be set to logic high simultaneously.
Figure 94 is a simplified diagram of the entire data capture
system in the AD9114/AD9115/AD9116/AD9117. The double
data rate input data (DB[n:0], where n is 7 for the AD9114, is 9
for the AD9115, is 11 for the AD9116, and 13 for the AD9117) is
latched at the pads/pins either on the rising edge or the falling edge
of the DCLKIO-INT clock, as determined by IRISING, Bit 4 of
SPI Address 0x02. Bit 5 of SPI Address 0x02, IFIRST, determines
which channel data is latched first (that is, I or Q). The captured
data is then retimed to the internal clock (CLKIN-INT) in the
retimer block before being sent to the final analog DAC core
(D-FF 4), which controls the current steering output switches. All
delay blocks depicted in Figure 94 are non-inverting, and any wires
without an explicit delay block can be assumed to have no delay.
Only one channel is shown in Figure 94 with the data pads
(DB[n:0], where n is 7 for the AD9114, is 9 for the AD9115, is
11 for the AD9116, and 13 for the AD9117) serving as double
data rate pads for both channels.
The default PINMD and SPI settings are IE = high (closed) and
OE = low (open). These settings are enabled when RESET/PINMD
(Pin 35) is held high. In this mode, the user has to supply both
DCLKIO and CLKIN. In PINMD, it is also recommended that the
DCLKIO and the CLKIN be in phase for proper functioning of
the DAC, which can easily be ensured by tying the pins together
on the PCB. If the user can access the SPI, setting Bit 2 of SPI
Address 0x02, DCI_EN, to logic low causes the CLKIN to be
used as the DCLKIO also.
Retimer
The AD9114/AD9115/AD9116/AD9117 have an internal data
retimer circuit that compares the CLKIN-INT and DCLKIO-INT
clocks and, depending on their phase relationship, selects a
retimer clock (RETIMER-CLK) to safely transfer data from the
DCLKIO used at the chip’s input interface to the CLKIN used to
clock the analog DAC cores (D-FF 4).
The retimer selects one of the three phases shown in Figure 95.
The retimer is controlled by the CLKMODE SPI bits as is
shown in Table 15.
DATA
CLOCK
1/2 PERIOD
RETIMER-CLKs
180°
90°
270°
1/4 PERIOD 1/2 PERIOD
Figure 95. RETIMER-CLK Phases
Note that, in most cases, more than one retimer phase works
and, in such cases, the retimer arbitrarily picks one phase that
works. The retimer cannot pick the best or safest phase. If the
user has a working knowledge of the exact phase relationship
between DCLKIO and CLKIN (and thus DCLKIO-INT and
CLKIN-INT because the delay is approximately the same for
both clocks and equal to DELAY1), then the retimer can be
forced to this phase with CLKMODEN = 1, as described in
Table 15 and the following paragraphs.
Rev. D | Page 41 of 52
 

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