AD7484BSTZ Analog Devices Inc, AD7484BSTZ Datasheet - Page 17

• Manufacturer Part Number: AD7484BSTZ
• Description: IC ADC 14BIT SAR 3MSPS 48-LQFP
• Manufacturer: Analog Devices Inc

Specifications of AD7484BSTZ

• Data Interface: Parallel
• Number Of Bits: 14
• Sampling Rate (per Second): 3M
• Number Of Converters: 1
• Power Dissipation (max): 90mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP
• Resolution (bits): 14bit
• Sampling Rate: 3MSPS
• Input Channel Type: Single Ended
• Supply Voltage Range - Analog: 4.75V To 5.25V
• Supply Voltage Range - Digital: 4.75V To 5.25V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: EVAL-AD7484CBZ - BOARD EVALUATION FOR AD7484
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Board Layout and Grounding
To obtain optimum performance from the AD7484, it is
recommended that a printed circuit board with a minimum of
three layers be used. One of these layers, preferably the middle
layer, should be as complete a ground plane as possible to give
the best shielding. The board should be designed in such a way
that the analog and digital circuitry is separated and confined to
certain areas of the board. This practice, along with avoiding
running digital and analog lines close together, should help to
avoid coupling digital noise onto analog lines.
The power supply lines to the AD7484 should be approximately
3 mm wide to provide low impedance paths and reduce the
effects of glitches on the power supply lines. It is vital that good
decoupling is also present. A combination of ferrites and
decoupling capacitors should be used, as shown in Figure 23.
The decoupling capacitors should be as close to the supply pins
as possible. This is made easier by the use of multilayer boards.
Figure 24.
Figure 25.
Figure 26.
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The signal traces from the AD7484 pins can be run on the top
layer, while the decoupling capacitors and ferrites can be
mounted on the bottom layer where the power traces exist. The
ground plane between the top and bottom planes provide
excellent shielding.
Figure 24 to Figure 28 show a sample layout of the board area
immediately surrounding the AD7484. Pin 1 is the bottom left
corner of the device. Figure 24 shows the top layer where the
AD7484 is mounted with vias to the bottom routing layer
highlighted. Figure 27 shows the bottom layer where the power
routing is with the same vias highlighted. Figure 25 shows the
bottom layer silkscreen where the decoupling components are
soldered directly beneath the device. Figure 28 shows the
silkscreen overlaid on the solder pads for the decoupling
components, and Figure 26 shows the top and bottom routing
layers overlaid. The black area in each figure indicates the
ground plane present on the middle layer.
C1 to C6: 100 nF, C7 to C8: 470 nF, C9: 1 nF
L1 to L4: Meggit-Sigma Chip Ferrite Beads (BMB2A0600RS2)
Figure 27.
Figure 28.
AD7484