CHAPTER 12 A/D CONVERTER
406
User’s Manual U14359EJ4V0UM
Figure 12-1. Block Diagram of A/D Converter
ANI0
ANI1
ANI2
ANI3
ANI4
ANI5
ANI6
ANI7
INTM000
INTM001
INTM010
INTM011
INTAD
Input circuit
ADM0 (8)
8
Voltage comparator
SAR (10)
ADCR0
ADCR1
ADCR2
ADCR3
ADCR4
ADCR5
ADCR6
ADCR7
10
10
10
9
0
Internal bus
Tap selector
AV
DD/
AV
REF
R/2
R
R/2
Series resistor string
7
0
ADM1 (8)
7
0
AV
SS
8
ADM2 (8)
7
0
8
Edge
detection
ADTRG
Controller
Sample & hold circuit
f
XX
/2
Remark
f
XX
: Internal system clock
Cautions 1. If there is noise at the analog input pins (ANI0 to ANI7) or at the reference voltage input
pin (AV
REF
), that noise may generate an illegal conversion result.
Software processing will be needed to avoid a negative effect on the system from this
illegal conversion result.
An example of this software processing is shown below.
••••
Take the average result of a number of A/D conversions and use that as the A/D
conversion result.
••••
Execute a number of A/D conversions consecutively and use those results, omitting
any exceptional results that may have been obtained.
••••
If an A/D conversion result that is judged to have generated a system malfunction is
obtained, be sure to recheck the system malfunction before performing malfunction
processing.
2. Do not apply a voltage outside the AV
SS
to AV
REF
range to the pins that are used as A/D
converter input pins.