EVAL-ADUC812QSZ Analog Devices Inc, EVAL-ADUC812QSZ Datasheet - Page 43

• Manufacturer Part Number: EVAL-ADUC812QSZ
• Description: Analog MCU Evaluation Board
• Manufacturer: Analog Devices Inc
• Series: QuickStart™ Kitr
• Type: MCUr

Specifications of EVAL-ADUC812QSZ

• Silicon Manufacturer: Analog Devices
• Core Architecture: 8051
• Silicon Core Number: ADuC812
• Tool / Board Applications: General Purpose MCU, MPU, DSP, DSC
• Mcu Supported Families: ADUC8xx
• Contents: Evaluation Board, Power Supply, Cable, Software and Documentation
• Development Tool Type: Hardware - Eval/Demo Board
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: ADuC812
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Grounding and Board Layout Recommendations
As with all high resolution data converters, special attention
must be paid to grounding and PC board layout of ADuC812
based designs in order to achieve optimum performance from
the ADC and DACs.
Although the ADuC812 has separate pins for analog and digital
ground (AGND and DGND), the user must not tie these to two
separate ground planes unless the two ground planes are connected
together very close to the ADuC812, as illustrated in the simpli-
fied example of Figure 45a. In systems where digital and analog
ground planes are connected together somewhere else (for example,
at the system’s power supply), they cannot be connected again
near the ADuC812 since a ground loop would result. In these
cases, tie the ADuC812’s AGND and DGND pins all to the
analog ground plane, as illustrated in Figure 45b. In systems with
only one ground plane, ensure that the digital and analog com-
ponents are physically separated onto separate halves of the board
such that digital return currents do not flow near analog circuitry
and vice versa. The ADuC812 can then be placed between the
digital and analog sections, as illustrated in Figure 45c.
REV. E
a.
b.
c.
Figure 45. System Grounding Schemes
PLACE ANALOG
COMPONENTS
PLACE ANALOG
PLACE ANALOG
COMPONENTS
COMPONENTS
HERE
AGND
AGND
HERE
HERE
–43–
GND
In all of these scenarios, and in more complicated real-life appli-
cations, keep in mind the flow of current from the supplies and
back to ground. Make sure the return paths for all currents are
as close as possible to the paths the currents took to reach their
destinations. For example, do not power components on the
analog side of Figure 45b with DV
return currents from DV
avoid digital currents flowing under analog circuitry, which could
happen if the user placed a noisy digital chip on the left half of the
board in Figure 45c. Whenever possible, avoid large discontinuities
in the ground plane(s) (formed by a long trace on the same
layer), since they force return signals to travel a longer path. And
of course, make all connections to the ground plane directly,
with little or no trace separating the pin from its via to ground.
If the user plans to connect fast logic signals (rise/fall time < 5 ns)
to any of the ADuC812’s digital inputs, add a series resistor to
each relevant line to keep rise and fall times longer than 5 ns at the
ADuC812 input pins. A value of 100 or 200 is usually suffi-
cient to prevent high speed signals from coupling capacitively
into the ADuC812 and affecting the accuracy of ADC conversions.
PLACE DIGITAL
PLACE DIGITAL
COMPONENTS
COMPONENTS
PLACE DIGITAL
COMPONENTS
HERE
HERE
HERE
DGND
DGND
DD
to flow through AGND. Also, try to
DD
since that would force
ADuC812