C8051F120/1/2/3/4/5/6/7 C8051F130/1/2/3
Rev. 1.4
115
9.2.
Reference Configuration on the C8051F121/3/5/7
On the C8051F121/3/5/7 devices, the REF0CN register also allows selection of the voltage reference
source for ADC0 and ADC2, as shown in SFR Definition 9.2. Bits AD0VRS and AD2VRS in the REF0CN
register select the ADC0 and ADC2 voltage reference sources, respectively. The VREFA pin provides a
voltage reference input for ADC0 and ADC2, which can be connected to an external precision reference or
the internal voltage reference. ADC0 may also reference the DAC0 output internally, and ADC2 may refer-
ence the analog power supply voltage, via the VREF multiplexers shown in Figure 9.2.
Figure 9.2. Voltage Reference Functional Block Diagram (C8051F121/3/5/7)
Recommended Bypass
Capacitors
x2
VREF
DAC0
DAC1
Ref
AV+
ADC2
ADC0
Ref
Ref
1
0
0
1
VREFA
4.7
μ
F
0.1
μ
F
External
Voltage
Reference
Circuit
R1
VDD
DGND
REF0CN
RE
F
B
E
BI
ASE
TE
M
P
E
AD
2VR
S
AD
0VR
S
REFBE
BIASE
Bias to
ADCs,
DACs
1.2V
Band-Gap
EN
+
Summary of Contents for C8051F12 Series
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