EVAL-ADUC842QSZ Analog Devices Inc, EVAL-ADUC842QSZ Datasheet - Page 75

• Manufacturer Part Number: EVAL-ADUC842QSZ
• Description: Analog MCU Evaluation Board
• Manufacturer: Analog Devices Inc
• Series: QuickStart™ Kitr
• Type: MCUr

Specifications of EVAL-ADUC842QSZ

• Silicon Manufacturer: Analog Devices
• Core Architecture: 8052
• Silicon Core Number: ADuC842
• 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: ADuC824
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

5 V Part
For DV
As DV
approximately 128 ms before the part is released from reset. The
user must ensure that the power supply has reached a stable
4.75 V minimum level by this time. Likewise on power-down,
the internal POR holds the part in reset until the power supply
has dropped below 1 V. Figure 83 illustrates the operation of the
internal POR in detail.
Grounding and Board Layout Recommendations
As with all high resolution data converters, special attention
must be paid to grounding and PC board layout of ADuC841/
ADuC842/ADuC843 based designs to achieve optimum
performance from the ADC and the DACs. Although the parts
have 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 part, as illustrated in the simplified example of
Figure 84a. 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
part since a ground loop would result. In these cases, tie all the
part’s AGND and DGND pins to the analog ground plane, as
illustrated in Figure 84b. In systems with only one ground plane,
ensure that the digital and analog components are physically
separated onto separate halves of the board such that digital
return currents do not flow near analog circuitry and vice versa.
The part can then be placed between the digital and analog
sections, as illustrated in Figure 84c.
In all of these scenarios, and in more complicated real-life
applications, 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 that the currents took to
DV
CORE RESET
INTERNAL
DD
DD
1.0V TYP
DD
rises above 4.5 V, an internal timer times out for
4.75V
below 4.5 V, the internal POR holds the part in reset.
Figure 83. Internal POR Operation
128ms
128ms
1.0V
Rev. 0 | Page 75 of 88
reach their destinations. For example, do not power components
on the analog side of Figure 84b with DV
force return currents from DV
try to avoid digital currents flowing under analog circuitry,
which could happen if the user places a noisy digital chip on the
left half of the board in Figure 84c. Whenever possible, avoid
large discontinuities in the ground plane(s) (like those formed
by a long trace on the same layer), since they force return
signals to travel a longer path. And of course, make all connec-
tions 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 part’s digital inputs, a series resistor should be
added to each relevant line to keep rise and fall times longer
than 5 ns at the part’s input pins. A value of 100
usually sufficient to prevent high speed signals from coupling
capacitively into the part and from affecting the accuracy of
ADC conversions.
a.
b.
c.
PLACE ANALOG
COMPONENTS
PLACE ANALOG
COMPONENTS
HERE
PLACE ANALOG
AGND
AGND
COMPONENTS
Figure 84. System Grounding Schemes
HERE
HERE
ADuC841/ADuC842/ADuC843
DD
GND
to flow through AGND. Also,
PLACE DIGITAL
COMPONENTS
PLACE DIGITAL
COMPONENTS
DD
PLACE DIGITAL
COMPONENTS
HERE
HERE
since that would
HERE
DGND
DGND
Ω
or 200
Ω
is