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Section 15 A/D Converter
15.5
Interrupts
The A/D converter generates an interrupt (ADI) at the end of A/D conversion. The ADI interrupt
request can be enabled or disabled by the ADIE bit in ADCSR.
15.6
Usage Notes
When using the A/D converter, note the following points:
1. Note on Board Design
In board layout, separate the digital circuits from the analog circuits as much as possible.
Particularly avoid layouts in which the signal lines of digital circuits cross or closely approach
the signal lines of analog circuits. Induction and other effects may cause the analog circuits to
operate incorrectly, or may adversely affect the accuracy of A/D conversion.
The analog input signals (AN
voltage (AV
) must be separated from digital circuits by the analog ground (AV
CC
analog ground (AV
board.
2. Note on Noise
To prevent damage from surges and other abnormal voltages at the analog input pins (AN
AN
) and analog reference voltage pin (V
7
figure 15.7 between AV
the filter capacitors connected to AN
like the ones in figure 15.7 are connected, the voltage values input to the analog input pins
(AN
to AN
) will be smoothed, which may give rise to error. Error can also occur if A/D
0
7
conversion is frequently performed in scan mode so that the current that charges and
discharges the capacitor in the sample-and-hold circuit of the A/D converter becomes greater
than that input to the analog input pins via input impedance R
therefore be selected carefully.
Rev. 3.00 Mar 21, 2006 page 536 of 814
REJ09B0302-0300
to AN
), analog reference voltage (V
0
7
) should be connected to a stable digital ground (V
SS
and AV
. The bypass capacitors connected to AV
CC
SS
to AN
0
), connect a protection circuit like the one in
REF
must be connected to AV
7
. The circuit constants should
in
), and analog supply
REF
). The
SS
) at one point on the
SS
and V
CC
REF
. If filter capacitors
SS
to
0
and
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