SN8P2711A
8-Bit Micro-Controller
SONiX TECHNOLOGY CO., LTD
Page 119
Version 0.1
S16:
ADC reference voltage selection. The reference voltage is connected to VREFH pin of CON1. The max. reference
voltage is VDD. If VDD < INT_VREFH_4.0V, the ADC reference voltage is VDD. EXT_VREFH is external reference
voltage selection and input from P4.0. Under internal reference conditions, P4.0 is general purpose I/O or ADC analog
input mode.
R26:
2K ohm VR to adjust ADC internal reference voltage. User have to correct internal reference voltage. Set S16 to
INT_VREFH_4.0V mode, input power VDD = 5V, measure internal reference voltage from J3. Adjust R26 to make J3
voltage = 4.0V.
VDD
R32
600
INT_VREFH
VIN
U2
LM431
VREFH
V40
V20
INT_VREFH_TP
C8
10uF
R33
1K
VIN
INT_VREFH
INT_VREFH
R27
100
V20
VREFH
VERFH
VIN
R31
200
VREFH
V30
VREFH_TP
S16
OFF ON
1
2
3
4
5
6
12
11
10
9
8
7
VDD
P4.0
C7
10uF
V40
VREFH
V30
R26
2K
VREFH
R34
2K
R36, P37:
R36=300K ohm, R37= 100K ohm. The bias voltage is equal to 1/4 VDD and emulates SN8P2711A internal
1/4 VDD voltage for low battery detector by ADC channel 5.
C9~C14:
Connect 47uF capacitors to AIN0~AIN5 input which are ADC channel 0~5 bypass capacitors.
C15~C20:
Connect 0.1uF capacitors to AIN0~AIN5 input which are ADC channel 0~5 bypass capacitors.
Switch No.
S1
S2
S3
S4
S5
S6
INT_VREFH_2.0V
ON ON OFF OFF OFF OFF
INT_VREFH_3.0V
OFF ON OFF OFF ON OFF
INT_VREFH_4.0V
OFF OFF ON OFF ON OFF
INT_VREFH_VDD
OFF OFF OFF ON OFF OFF
EXT_VREFH OFF OFF OFF OFF OFF ON