Precautions For A-D Converter - Renesas M16C/26 Series Reference Book

Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
M16C/26 Group

1.8 Precautions for A-D Converter

1. Set ADCON0 (except bit 6), ADCON1 and ADCON2 registers when A-D conversion is stopped (before
a trigger occurs).
2. When the VCUT bit of ADCON1 register is changed from "0" (Vref not connected) to "1" (Vref con-
nected), start A-D conversion after passing 1 µs or longer.
3. To prevent noise-induced device malfunction or latchup, as well as to reduce conversion errors, insert
capacitors between the AV
Similarly, insert a capacitor between the V
tion of each pin.
4. Make sure the port direction bits for those pins that are used as analog inputs are set to "0" (input
mode). Also, if the ADCON0 register's TGR bit = 1 (external trigger), make sure the port direction bit for
___________
the AD pin is set to "0" (input mode).
TRG
5. When using key input interrupts, do not use any of the four AN
input interrupt request is generated when the A-D input voltage goes low.)
6. The φ frequency must be 10 MHz or less. Without sample-and-hold function, limit the φ
AD
or more. With the sample and hold function, limit the φ
to 250kH
Z
7. When changing an A-D operation mode, select analog input pin again in the CH2 to CH0 bits of
ADCON0 register and the SCAN1 to SCAN0 bits of ADCON1 register.
Figure 1.8.1. Use of capacitors to reduce noise
Rev.0.90 2003.12.28 page 19 of 28
, V , and analog input pins (ANi(i=0 to 7)) each and the AV
CC REF
Microcomputer
V
CC
V
CC
C4
V
SS
ANi: ANi (i=0 to 7)
Note 1: C1≥0.47µF, C2 ≥0.47µF, C3 ≥100pF, C4≥0.1µF (reference)
Note 2: Use thick and shortest possible wiring to connect capacitors.
pin and the V pin. Figure 1.8.1 is an example connec-
CC SS
to AN
4
AD
AV
CC
V
REF
C2
C1
AV
SS
C3
ANi
1.8 Precautions for A-D Converter
pins as analog inputs. (A key
7
frequency
AD
frequency to 1MH or more.
Z
V
CC
pin.
SS