AD962711-105EBZ Analog Devices Inc, AD962711-105EBZ Datasheet - Page 47

• Manufacturer Part Number: AD962711-105EBZ
• Description: EVAL For 11bit 105 Dual 1.8V
• Manufacturer: Analog Devices Inc

Specifications of AD962711-105EBZ

• Number Of Adc's: 2
• Number Of Bits: 11
• Sampling Rate (per Second): 105M
• Data Interface: Serial
• Inputs Per Adc: 1 Differential
• Input Range: 1 ~ 2 Vpp
• Power (typ) @ Conditions: 600mW @ 105MSPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD962711
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
DESIGN GUIDELINES
Before starting design and layout of the AD9627-11 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 AD9627-11, it is recommended
that two separate 1.8 V supplies be used: one supply should be used
for analog (AVDD) and digital (DVDD), and a separate supply
should be used for the digital outputs (DRVDD). The AVDD
and DVDD supplies, while derived from the same source, should
be isolated with a ferrite bead or filter choke and separate
decoupling capacitors. The designer can employ several
different decoupling capacitors to cover both high and low
frequencies. These capacitors should be located close to the
point of entry at the PC board level and close to the pins of the
part, with minimal trace length.
A single PCB ground plane should be sufficient when using the
AD9627-11. With proper decoupling and smart partitioning of
the PCB analog, digital, and clock sections, optimum
performance is easily achieved.
LVDS Operation
The AD9627-11 defaults to CMOS output mode on power-up.
If LVDS operation is desired, this mode must be programmed
using the SPI configuration registers after power-up. When the
AD9627-11 powers up in CMOS mode with LVDS termination
resistors (100 Ω) on the outputs, the DRVDD current can be
higher than the typical value until the part is placed in LVDS
mode. This additional DRVDD current does not cause damage
to the AD9627-11, but it should be taken into account when
considering the maximum DRVDD current for the part.
To avoid this additional DRVDD current, the AD9627-11
outputs can be disabled at power-up by taking the OEB pin high.
After the part is placed into LVDS mode via the SPI port, the
OEB pin can be taken low to enable the outputs.
Exposed Paddle Thermal Heat Slug Recommendations
It is mandatory that the exposed paddle on the underside of the
ADC be connected to analog ground (AGND) to achieve the
best electrical and thermal performance. A continuous, exposed
(no solder mask), copper plane on the PCB should mate to the
AD9627-11 exposed paddle, Pin 0.
Rev. A | Page 47 of 72
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. These vias should be filled or
plugged with nonconductive epoxy.
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. See the evalua-
tion board for a PCB layout example. For detailed information
about packaging and PCB layout of chip scale packages, see
Application Note AN-772, A Design and Manufacturing Guide
for the Lead Frame Chip Scale Package (LFCSP).
CML
The CML pin should be decoupled to ground with a 0.1 μF
capacitor, as shown in Figure 47.
RBIAS
The AD9627-11 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
The VREF pin should be externally decoupled 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
AD9627-11 to keep these signals from transitioning at the
converter inputs during critical sampling periods.
AD9627-11