RX610 Group
23. A/D Converter
R01UH0032EJ0120 Rev.1.20
Page 803 of 1006
Feb 20, 2013
23.6.7
Ranges of Settings for Analog Power Supply and Other Pins
Using this LSI circuit with voltages beyond the ranges given below can have a bad effect on LSI reliability.
•
Range for the setting of analog input voltages
Keep voltages applied to analog input pins (ANn pins) within the range defined by V
REFL
≤ V
AN
≤ V
REFH
.
•
Relations between AVcc and AVss, V
REFH
and V
REFL
, and Vcc and Vss
Ensure that the relations between AVcc and AVss and between Vcc and Vss are AVcc = Vcc and AVss = Vss.
To realize AVcc = Vcc and AVss = Vss at the points where the power-supply lines originate, set up closed loops with
wiring runs between power-supply pins that are as short as possible and connect 0.1-μF capacitors as shown in figure
23.16. Even if the A/D converters are not in use, ensure that V
REFH
= AVcc = Vcc and V
REFL
= AVss = Vss by making
the same connections.
•
Range for the setting of V
REFH
Keep the reference voltage on the V
REFH
pin within the range defined by V
REFH
≤ AVcc.
VCC
AVCC
AVSS
VREFH
VSS
0.1 µF
0.1 µF
VREFL
0.1 µF
Figure 23.16 Example of Connection for Power-Supply Pins
23.6.8
Point for Caution Regarding Board Design
As far as possible, separate the analog circuits from the digital circuits in board design. Furthermore, do not allow the
wiring runs for a signal of a digital circuit and a signal of an analog circuit to cross or be in each other's vicinity.
Inductive coupling leads to analog circuits operating incorrectly and has a bad effect on the results of analog conversion.
Keep the signal lines for analog input pins (AN0 to AN15), the analog reference power supply pin (V
REFH
), the analog
power-supply voltage (AVcc), and analog ground (AVSS) away from digital circuitry. Furthermore, connect the analog
reference ground (V
REFL
) to the stabilized ground (Vss) on the board at a single point.
Summary of Contents for RX600 Series
Page 1006: ...RX610 Group R01UH0032EJ0120 ...