C8051F960-B-GM Datasheet, PDF (100/492 Pages) Silicon Laboratories – Ultra Low Power 128K, LCD MCU Family

C8051F96x
5.9. Voltage and Ground Reference Options
The voltage reference MUX is configurable to use an externally connected voltage reference, the internal
voltage reference, or one of two power supply voltages (see Figure 5.10). The ground reference MUX
allows the ground reference for ADC0 to be selected between the ground pin (GND) or a port pin dedi-
cated to analog ground (P0.1/AGND).
The voltage and ground reference options are configured using the REF0CN SFR described on SFR
Definition 5.15. REF0CN: Voltage Reference Control. Electrical specifications are can be found in the
Electrical Specifications Chapter.
Important Note About the V_REF and AGND Inputs: Port pins are used as the external V_REF and AGND
inputs. When using an external voltage reference or the internal precision reference, P0.0/VREF should be
configured as an analog input and skipped by the Digital Crossbar. When using AGND as the ground refer-
ence to ADC0, P0.1/AGND should be configured as an analog input and skipped by the Digital Crossbar.
Refer to Section “27. Port Input/Output” on page 351 for complete Port I/O configuration details. The exter-
nal reference voltage must be within the range 0  V_REF  VDD and the external ground reference must be
at the same dc voltage potential as GND.
REF0CN
Temp Sensor
EN
ADC
Input
Mux
VDD
R1
E x te rn a l
V o lta g e
R e fe re n c e
C irc u it
P 0 .0 /V R E F
VBAT
GND
+
4.7F
0.1F
GND
Recommended
Bypass Capacitors
P 0 .1 /A G N D
00
01
Internal 1.8V
10
Regulated Digital Supply
11
Internal 1.65V
High Speed Reference
0
1
REFGND
Figure 5.10. Voltage Reference Functional Block Diagram
VREF
(to ADC)
Ground
(to ADC)
100
Rev. 1.0