3069RF-ZTAT Datasheet, PDF (579/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

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. The ADI interrupt request can be
designated as a DMAC activation source. In this case, an interrupt request is not sent to the CPU.
15.6 Usage Notes
When using the A/D converter, note the following points:
1. Analog Input Voltage Range: During A/D conversion, the voltages input to the analog input
pins should be in the range AV_SS ≤ AN_n ≤ V_REF.
2. Relationships of AV_CC and AV_SS to V_CC and V_SS: AV_CC, AV_SS, V_CC, and V_SS should be related as
follows: AV_SS = V_SS. AV_CC and AV_SS must not be left open, even if the A/D converter is not
used.
3. V_REF Programming Range: The reference voltage input at the V_REF pin should be in the range
V_REF ≤ AV_CC.
4. 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.
5. 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 Rin. The circuit constants should
therefore be selected carefully.
Rev. 5.0, 09/04, page 557 of 978