R01UH0823EJ0100 Rev.1.00
Page 1619 of 1823
Jul 31, 2019
RX23W Group
44. 12-Bit A/D Converter (S12ADE)
44.8.12
Notes on Board Design
The board should be designed so that digital circuits and analog circuits are separated from each other as far as possible.
In addition, digital circuit signal lines and analog circuit signal lines should not intersect or placed near each other. If
these rules are not followed, noise will be produced on analog signals and A/D conversion accuracy will be affected. The
analog input pins (AN000 to AN007, AN016 to AN020, AN027), reference power supply pin (VREFH0), reference
ground pin (VREFL0), and analog power supply (AVCC0) should be separated from digital circuits using the analog
ground (AVSS0). The analog ground (AVSS0) should be connected to a stable digital ground (VSS) on the board (single-
point ground plane connection).
44.8.13
Notes on Noise Prevention
To prevent the analog input pins (AN000 to AN007, AN016 to AN020, AN027) from being destroyed by abnormal
voltage such as excessive surge, a capacitor should be inserted between AVCC0 and AVSS0 and between VREFH0 and
VREFL0, and a protection circuit should be connected to protect the analog input pins (AN000 to AN007, AN016 to
AN020, AN027) as shown
Figure 44.32
Sample Protection Circuit for Analog Inputs
Rin
*2
10 µF
0.01 µF
*1
*1
0.1 µF
0.1 µF
Note 1.
The values shown here are reference values.
Note 2.
Rin: Signal source impedance
AVCC0
VREFH0
AN000 to AN007,
AN016 to AN020, AN027
AVSS0
VREFL0