A/D Converter Reference Voltage - Holtek BS86DH12C Manual

BS86DH12C
High Voltage Touch A/D Flash MCU with HVIO
• SADC1 Register
Bit 7
Name SAINS2
R/W R/W
POR 0
Bit 7~5 SAINS2~SAINS0: A/D converter input signal selection
000: External source – External analog channel intput, ANn
001: Internal source – Internal bandgap reference voltage, V
010: Internal source – Internal high voltage power VCC1 divided voltage, V
011: Internal source – Internal high voltage power VCC2 divided voltage, V
100: Internal source – Internal OCP operational amplifier output voltage, V
101~111: External source – External analog channel input, ANn
Care must be taken if the SAINS field is set to "001~100" to select the internal analog
signal to be converted. When the internal analog signal is selected to be converted, the
external channel input pin must never be selected as the A/D input signal by properly
setting the SACS bit field with a value of "1000~1111". Otherwise, the external
channel input will be connected together with the internal analog signal. This will
result in unpredictable situations such as an irreversible damage.
Bit 4~3 SAVRS1~SAVRS0: A/D converter reference voltage selection
00: External VREF pin
01: Internal A/D converter power, AV
1x: External VREF pin
These bits are used to select the A/D converter reference voltage source. Care must
be taken if the SAVRS field is set to "01" to select the internal A/D converter power
voltage as the reference voltage source. When the internal reference voltage source is
selected, the external VREF pin cannot be configured as the reference voltage input by
properly configuring the relevant pin-shared control bits. Otherwise, the external input
voltage on the VREF pin will be connected to the internal A/D converter power. This
will result in unpredictable situations.
Bit 2~0 SACKS2~SACKS0: A/D conversion clock source selection
000: f
001: f
010: f
011: f
100: f
101: f
110: f
111: f
These bits are used to select the clock source for the A/D converter.

A/D Converter Reference Voltage

The actual reference voltage supply to the A/D converter can be supplied from the positive power
supply, AV , or an external reference source supplied on pin VREF determined by the SAVRS
DD
bit field in the SADC1 register. When the SAVRS field is set to "01", the A/D converter reference
voltage will come from the AV
from the VREF pin if the SAVRS field is set to any other value except "01". When the VREF pin
is selected as the reference voltage supply pin, the relevant pin-shared control bits should first
be properly configured to enable the VREF pin function as it is pin-shared with other functions.
However, if the internal A/D converter power is selected as the reference voltage, the external VREF
pin must not be configured as the reference voltage input function to avoid the internal connection
between the VREF pin to the internal A/D converter power. Note that the analog input values must
not be allowed to exceed the value of the selected reference voltage.
Rev. 1.00
6 5 4
SAINS1 SAINS0 SAVRS1
R/W R/W R/W
0 0 0
SYS
/2
SYS
/4
SYS
/8
SYS
/16
SYS
/32
SYS
/64
SYS
/128
SYS
. Otherwise, the A/D converter reference voltage will come
DD
107
3 2 1
SAVRS0 SACKS2 SACKS1
R/W R/W R/W
0 0 0
BG
DD
October 26, 2018
0
SACKS0
R/W
0
CC1O
CC2O
OCPAO