C8051F709-GQR Silicon Labs, C8051F709-GQR Datasheet - Page 69

• Manufacturer Part Number: C8051F709-GQR
• Description: 8-bit Microcontrollers - MCU 8kB 32B EEPROM Cap Sense
• Manufacturer: Silicon Labs

Specifications of C8051F709-GQR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

12. Voltage and Ground Reference Options
The voltage reference MUX is configurable to use an externally connected voltage reference, the on-chip
voltage reference, or one of two power supply voltages (see Figure 12.1). 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 page 71.
Electrical specifications are can be found in the Electrical Specifications Chapter.
Important Note About the V
inputs. When using an external voltage reference, P0.0/VREF should be configured as an analog input and
skipped by the Digital Crossbar. When using AGND as the ground reference to ADC0, P0.1/AGND should
be configured as an analog input and skipped by the Digital Crossbar. Refer to Section “28. Port Input/Out-
put” on page 180 for complete Port I/O configuration details. The external reference voltage must be within
the range 0  V
GND.
4.7 uF
Bypass Capacitors
Recommended
GND
VDD
+
R1
Reference
External
Voltage
Circuit
0.1 uF
REF
Figure 12.1. Voltage Reference Functional Block Diagram
 V
P0.1/AGND
P0.0/VREF
DD
GND
and the external ground reference must be at the same DC voltage potential as
V
DD
REF
and AGND Inputs: Port pins are used as the external V
Regulated Digital Supply
High Speed Reference
REF0CN
Internal 1.8 V
Internal 1.6 V
Rev. 1.0
IOSCEN
EN
EN
REFGND
Bias Generator
Temp Sensor
0
1
00
01
10
11
C8051F70x/71x
To Analog Mux
To ADC, Internal
Oscillator,
Reference,
TempSensor
REF
and AGND
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