AD9649-65EBZ Analog Devices Inc, AD9649-65EBZ Datasheet - Page 30

• Manufacturer Part Number: AD9649-65EBZ
• Description: 14-Bit, 65 MSPS, A/D Converter Eval. Board
• Manufacturer: Analog Devices Inc

Specifications of AD9649-65EBZ

• Silicon Manufacturer: Analog Devices
• Application Sub Type: ADC
• Kit Application Type: Data Converter
• Silicon Core Number: AD9649
• Msl: MSL 3 - 168 Hours
• Mcu Supported Families: AD9649BCPZ-65
• Number Of Adc's: 1
• Number Of Bits: 14
• Sampling Rate (per Second): 65M
• Data Interface: Serial, SPI™
• Inputs Per Adc: 1 Differential
• Input Range: 2 Vpp
• Power (typ) @ Conditions: 82.3mW @ 65MSPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9649
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD9649
APPLICATIONS INFORMATION
DESIGN GUIDELINES
Before starting the design and layout of the AD9649 as a system,
it is recommended that the designer become familiar with these
guidelines, which discuss the special circuit connections and
layout requirements needed for certain pins.
Power and Ground Recommendations
When connecting power to the AD9649, it is strongly recom-
mended that two separate supplies be used. Use one 1.8 V supply
for analog (AVDD); use a separate 1.8 V to 3.3 V supply for the
digital output supply (DRVDD). If a common 1.8 V AVDD and
DRVDD supply must be used, the AVDD and DRVDD domains
must be isolated with a ferrite bead or filter choke and separate
decoupling capacitors. Several different decoupling capacitors can
be used to cover both high and low frequencies. Locate these
capacitors close to the point of entry at the PCB level and close
to the pins of the part, with minimal trace length.
A single PCB ground plane should be sufficient when using the
AD9649. With proper decoupling and smart partitioning of the
PCB analog, digital, and clock sections, optimum performance
is easily achieved.
Exposed Paddle Thermal Heat Sink Recommendations
The exposed paddle (Pin 0) is the only ground connection for
the AD9649; therefore, it must be connected to analog ground
(AGND) on the customer’s PCB. To achieve the best electrical
and thermal performance, mate an exposed (no solder mask)
continuous copper plane on the PCB to the AD9649 exposed
paddle, Pin 0.
The copper plane should have several vias to achieve the lowest
possible resistive thermal path for heat dissipation to flow through
the bottom of the PCB. Fill or plug these vias with nonconduc-
tive epoxy.
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To maximize the coverage and adhesion between the ADC and
the PCB, a silkscreen should be overlaid to partition the continuous
plane on the PCB into several uniform sections. This provides
several tie points between the ADC and the PCB during the reflow
process. Using one continuous plane with no partitions guarantees
only one tie point between the ADC and the PCB. For detailed
information about packaging and PCB layout of chip scale
packages, see the AN-772 Application Note, A Design and
Manufacturing Guide for the Lead Frame Chip Scale Package
(LFCSP), at www.analog.com.
Encode Clock
For optimum dynamic performance, use a low jitter encode
clock source with a 50% duty cycle (±5%) to clock the AD9649.
VCM
The VCM pin should be decoupled to ground with a 0.1 μF
capacitor, as shown in Figure 39.
RBIAS
The AD9649 requires that a 10 kΩ resistor be placed between
the RBIAS pin and ground. This resistor sets the master current
reference of the ADC core and should have at least a 1% tolerance.
Reference Decoupling
Externally decouple the VREF pin to ground with a low ESR,
1.0 μF capacitor in parallel with a low ESR, 0.1 μF ceramic
capacitor.
SPI Port
The SPI port should not be active during periods when the full
dynamic performance of the converter is required. Because the
SCLK, CSB, and SDIO signals are typically asynchronous to the
ADC clock, noise from these signals can degrade converter
performance. If the on-board SPI bus is used for other devices,
it may be necessary to provide buffers between this bus and the
AD9649 to keep these signals from transitioning at the converter
inputs during critical sampling periods.