Precautions For A-D Converter - Renesas M16C/60 Series Hardware Manual

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M16C/6N5 Group

1.10 Precautions for A-D Converter

1. Set the ADCON0 (except bit 6), ADCON1 and ADCON2 registers when A-D conversion is stopped
(before a trigger occurs).
2. When the VCUT bit of the ADCON1 register is changed from "0" (V
connected), 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
AV pin. Similarly, insert a capacitor between the V
SS
connection 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 TGR bit of the ADCON0 register = 1 (external trigger), make sure the port direction
__________
bit for the AD
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
to 250 kHz or more. With the sample and hold function, limit the φ
7. When changing an A-D operation mode, select analog input pin again in the CH2 to CH0 bits of the
ADCON0 register and the SCAN1 to SCAN0 bits of the ADCON1 register.
AN
Note 1: C1 ≥ 0.47 µF, C2 ≥ 0.47 µF, C3 ≥ 100 pF, C4 ≥ 0.1 µF (reference).
Note 2: Use thick and shortest possible wiring to connect capacitors.
Figure 1.10.1 Use of capacitors to reduce noise
Rev.1.00 2003.05.30 page 16
, V , and analog input pins (AN
CC REF
pin is set to "0" (input mode).
Microcomputer
V AV
CC
C4
V
V AV
SS
: AN , AN , and AN (i =0 to 7)
i i 0i 2i
(i = 0 to 7), AN
i
pin and the V
CC
to AN
4
AD
CC
REF
C2
C1
SS
C3
AN
i
1.10 Precautions for A-D Converter
not connected) to "1" (V
REF
, and AN ) each and the
0i 2i
pin. Figure 1.10.1 is an example
SS
pins as analog inputs. (A key
7
frequency
AD
frequency to 1 MHz or more.
REF