MC81F4216 Datasheet, PDF (147/200 Pages) Finechips – ABOV SEMICONDUCTOR 8-BIT SINGLE-CHIP MICROCONTROLLERS

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_SS to V_REF.
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
C 104
VREF
Analog Input VAIN
(*NOTE1)
C 104
ADC input port
VSS
MCU
Figure 22-2 Recommended A/D Converter Circuit
Note :
1. Lay out the GND of V_AIN as close as possible to the power source.
October 19, 2009 Ver.1.35
147