HD6473032F16 Datasheet, PDF (566/847 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

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 (AN₀ to AN₇), analog reference voltage (V_REF), and analog supply
voltage (AV_CC) must be separated from digital circuits by the analog ground (AV_SS). The
analog ground (AV_SS) should be connected to a stable digital ground (V_SS) at one point on the
board.
2. Note on Noise
To prevent damage from surges and other abnormal voltages at the analog input pins (AN₀ to
AN₇) and analog reference voltage pin (V_REF), connect a protection circuit like the one in
figure 15.7 between AV_CC and AV_SS. The bypass capacitors connected to AV_CC and V_REF and
the filter capacitors connected to AN₀ to AN₇ must be connected to AV_SS. If filter capacitors
like the ones in figure 15.7 are connected, the voltage values input to the analog input pins
(AN₀ to AN₇) will be smoothed, which may give rise to error. Error can also occur if A/D
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_in. The circuit constants should
therefore be selected carefully.
Rev. 3.00 Mar 21, 2006 page 536 of 814
REJ09B0302-0300