MC81F4x16
22.4 Internal Reference Voltage
In the ADC function block, the analog input voltage level is compared to the reference voltage. The
analog input level must be remained within the range V to V
.
REF
SS
Different reference voltage levels are generated internally along the resistor tree during the analog
conversion process for each conversion step. The reference voltage level for the first conversion bit is
always 1/2 V
.
REF
22.5 Recommended Circuit
VDD
VDD
+
-
10 F
C
104
VREF
C
104
Analog Input
VAIN
ADC input port
C
104
(*NOTE1)
VSS
MCU
Figure 22-2 Recommended A/D Converter Circuit
Note :
1. Lay out the GND of VAIN as close as possible to the power source.
October 19, 2009 Ver.1.35
147
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