AD9639 Analog Devices, Inc., AD9639 Datasheet - Page 35

• Manufacturer Part Number: AD9639
• Description: Quad, 12-bit, 170 Msps/210 Msps Serial Output 1.8 V Adc
• Manufacturer: Analog Devices, Inc.

APPLICATIONS INFORMATION
POWER AND GROUND RECOMMENDATIONS
When connecting power to the AD9639, it is recommended
that two separate 1.8 V supplies be used: one for analog (AVDD)
and one for digital (DRVDD). If only one supply is available, it
should be routed to the AVDD pin first and then tapped off and
isolated with a ferrite bead or a filter choke preceded by decou-
pling capacitors for the DRVDD pin. 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 parts, with minimal trace lengths.
A single PCB ground plane should be sufficient when using the
AD9639. With proper decoupling and smart partitioning of the
analog, digital, and clock sections of the PCB, optimum perfor-
mance can easily be achieved.
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EXPOSED PADDLE THERMAL HEAT SLUG
RECOMMENDATIONS
It is required that the exposed paddle on the underside of the
ADC be connected to analog ground (AGND) to achieve the best
electrical and thermal performance of the AD9639. An exposed
continuous copper plane on the PCB should mate to the AD9639
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. These vias
should be solder-filled or plugged with nonconductive epoxy.
To maximize the coverage and adhesion between the ADC and
PCB, partition the continuous copper plane into several uniform
sections by overlaying a silkscreen on the PCB. This provides
several tie points between the ADC and PCB during the reflow
process, whereas using one continuous plane with no partitions
guarantees only one tie point. See Figure 64 for a PCB layout
example. For detailed information on packaging and the 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.
SILKSCREEN PARTITION
PIN 1 INDICATOR
Figure 64. Typical PCB Layout
AD9639