AD9430-LVDS/PCB Analog Devices Inc, AD9430-LVDS/PCB Datasheet - Page 26

• Manufacturer Part Number: AD9430-LVDS/PCB
• Description: BOARD EVAL FOR AD9430-LVDS
• Manufacturer: Analog Devices Inc

Specifications of AD9430-LVDS/PCB

• Rohs Status: RoHS non-compliant
• Number Of Adc's: 1
• Number Of Bits: 12
• Sampling Rate (per Second): 210M
• Data Interface: Parallel
• Inputs Per Adc: 1 Differential
• Input Range: 1.5 Vpp
• Power (typ) @ Conditions: 1.5W @ 210MSPS
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9430

AD9430
ANALOG INPUT
The analog input to the AD9430 is a differential buffer. For
best dynamic performance, impedances at VIN+ and VIN–
should match. The analog input is optimized to provide
superior wideband performance and requires that the analog
inputs be driven differentially. SNR and SINAD performance
degrades significantly if the analog input is driven with a single-
ended signal.
A wideband transformer such as the Mini-Circuit® ADT1-1WT
can provide the differential analog inputs for applications that
require a single-ended-to-differential conversion. Both analog
inputs are self-biased by an on-chip resistor divider to a
nominal 2.8 V. (See the Equivalent Circuits section.)
Special care was taken in the design of the analog input section
of the AD9430 to prevent damage and corruption of data when
the input is overdriven. The nominal differential input range is
approximately 1.5 V p-p ~ (768 mV × 2). Note that the best
SNR performance is achieved with S5 = 0 (full scale = 1.5).
768mV
768mV
2.8V
2.8V
VIN+
VIN–
S5 = GND
S5 = AVDD
DIGITALOUT = ALL 1s
Figure 53. Single-Ended Analog Input Range
Figure 52. Differential Analog Input Range
VIN–
=
2.8V
VIN+
DIGITALOUT = ALL 0s
2.8V
2.8V
Rev. E | Page 26 of 44
DS INPUTS (DS+, DS–)
In CMOS output mode, the data sync inputs (DS+, DS–) can be
used in applications that require a given sample to appear at a
specific output port (A or B) relative to a given external timing
signal. The DS inputs can also be used to synchronize two or
more ADCs in a system to maintain phasing between Port A
and Port B on separate ADCs (in effect, synchronizing multiple
DCO outputs). When DS+ is held high (DS– low), the ADC
data outputs and clock do not switch and are held static.
Synchronization is accomplished by the assertion (falling edge)
of DS+ within the timing constraints t
clock rising edge. (On initial synchronization, t
relevant.) If DS+ falls within the required setup time (t
before a given clock rising edge, N, the analog value at that
point in time is digitized and available at Port A, 14 cycles later
in interleaved mode.
The very next sample, N + 1, is sampled by the next rising clock
edge and available at Port B, 14 cycles after that clock edge. In
dual-parallel mode, Port A has a 15-cycle latency and Port B
has a 14-cycle latency, but data is available at the same time.
Driving the DS inputs of each ADC by the same sync signal
accomplishes this. An easy way to accomplish synchronization
is by a one-time sync at power-on reset. Note that when
running the AD9430 in LVDS mode, set DS+ to ground and
DS– to 3.3 V, as the DS inputs are relevant only in CMOS
output mode, simplifying the design for some applications as
well as affording superior SNR/SINAD performance at higher
encode/analog frequencies.
CMOS OUTPUTS
The off-chip drivers on the chip can be configured to provide
CMOS-compatible output levels via Pin S2. The CMOS digital
outputs (S2 = 0) are TTL/CMOS compatible for lower power
consumption. The outputs are biased from a separate supply
(DRVDD), allowing easy interface to external logic. The outputs
are CMOS devices that swing from ground to DRVDD (with no
dc load). It is recommended to minimize the capacitive load the
ADC drives by keeping the output traces short (<1 inch, for a
total C
recommended to place low value (20 Ω) series damping
resistors on the data lines to reduce switching transient effects
on performance.
LOAD
< 5 pF). When operating in CMOS mode, it is also
SDS
and t
HDS
HDS
, relative to a
is not
SDS
)