Analog Devices AD9233 Evaluation Board AD9233-80EBZ AD9233-80EBZ Fiche De Données
Codes de produits
AD9233-80EBZ
AD9233
Rev. A | Page 27 of 44
LAYOUT CONSIDERATIONS
POWER AND GROUND RECOMMENDATIONS
When connecting power to the AD9233, it is recommended
that two separate supplies be used: one for analog (AVDD, 1.8 V
nominal) and one for digital (DRVDD, 1.8 V to 3.3 V nominal).
If only a single 1.8 V supply is available, then it should be routed
to AVDD first, then tapped off and isolated with a ferrite bead
or filter choke with decoupling capacitors preceding its con-
nection to DRVDD. The user can employ several different
decoupling capacitors to cover both high and low frequencies.
These should be located close to the point of entry at the PC
board level and close to the parts with minimal trace length.
that two separate supplies be used: one for analog (AVDD, 1.8 V
nominal) and one for digital (DRVDD, 1.8 V to 3.3 V nominal).
If only a single 1.8 V supply is available, then it should be routed
to AVDD first, then tapped off and isolated with a ferrite bead
or filter choke with decoupling capacitors preceding its con-
nection to DRVDD. The user can employ several different
decoupling capacitors to cover both high and low frequencies.
These should be located close to the point of entry at the PC
board level and close to the parts with minimal trace length.
A single PC board ground plane should be sufficient when
using the AD9233. With proper decoupling and smart parti-
tioning of the analog, digital, and clock sections of the board,
optimum performance is easily achieved.
using the AD9233. With proper decoupling and smart parti-
tioning of the analog, digital, and clock sections of the board,
optimum performance is easily achieved.
Exposed Paddle Thermal Heat Slug Recommendations
It is required that the exposed paddle on the underside of the
ADC is connected to analog ground (AGND) to achieve the
best electrical and thermal performance of the AD9233. An
exposed, continuous copper plane on the PCB should mate to
the AD9233 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.
ADC is connected to analog ground (AGND) to achieve the
best electrical and thermal performance of the AD9233. An
exposed, continuous copper plane on the PCB should mate to
the AD9233 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.
To maximize the coverage and adhesion between the ADC and
PCB, partition the continuous plane by overlaying a silkscreen
on the PCB into several uniform sections. This provides several
tie points between the two during the reflow process. Using one
continuous plane with no partitions only guarantees one tie
point between the ADC and PCB. See Figure 58 for a PCB
layout example. For detailed information on packaging and the
PCB layout of chip scale packages, see Application Note
PCB, partition the continuous plane by overlaying a silkscreen
on the PCB into several uniform sections. This provides several
tie points between the two during the reflow process. Using one
continuous plane with no partitions only guarantees one tie
point between the ADC and PCB. See Figure 58 for a PCB
layout example. For detailed information on packaging and the
PCB layout of chip scale packages, see Application Note
A Design and Manufacturing Guide for the Lead Frame Chip
Scale Package (LFCSP).
Scale Package (LFCSP).
SILKSCREEN PARTITION
PIN 1 INDICATOR
0
549
2-
0
54
Figure 58. Typical PCB Layout
CML
The CML pin should be decoupled to ground with a 0.1 μF
capacitor, as shown in Figure 38.
capacitor, as shown in Figure 38.
RBIAS
The AD9233 requires the user to place a 10 kΩ resistor between
the RBIAS pin and ground. This resister sets the master current
reference of the ADC core and should have at least a 1% tolerance.
the RBIAS pin and ground. This resister 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 0.1 μF ceramic low
ESR capacitor. In all reference configurations, REFT and REFB
are bypass points provided for reducing the noise contributed
by the internal reference buffer. It is recommended to place an
external 0.1 μF ceramic capacitor across REFT/REFB. While it is
not required to place this 0.1 μF capacitor, the SNR performance
will degrade by approximately 0.1 dB without it. All reference
decoupling capacitors should be placed as close to the ADC as
possible with minimal trace lengths.
low ESR 1.0 μF capacitor in parallel with a 0.1 μF ceramic low
ESR capacitor. In all reference configurations, REFT and REFB
are bypass points provided for reducing the noise contributed
by the internal reference buffer. It is recommended to place an
external 0.1 μF ceramic capacitor across REFT/REFB. While it is
not required to place this 0.1 μF capacitor, the SNR performance
will degrade by approximately 0.1 dB without it. All reference
decoupling capacitors should be placed as close to the ADC as
possible with minimal trace lengths.