C8051T603 View Datasheet(PDF) - Silicon Laboratories
Part Name
Description
MFG CO.
'C8051T603' PDF : 168 Pages View PDF
C8051T600/1/2/3/4/5/6
11. Voltage Reference Options
The voltage reference multiplexer for the ADC is configurable for use with an externally connected voltage
reference, the unregulated power supply voltage (VDD), or the regulated 1.8 V internal supply (see
Figure 11.1). The REFSL bit in the Reference Control register (REF0CN, SFR Definition 11.1) selects the
reference source for the ADC. For an external source, REFSL should be set to 0 to select the VREF pin. To
use VDD as the reference source, REFSL should be set to 1. To override this selection and use the internal
regulator as the reference source, the REGOVR bit can be set to 1. The electrical specifications for the
voltage reference circuit are given in Section “8. Electrical Characteristics” on page 30.
Important Note about the VREF Pin: When using an external voltage reference, the VREF pin should be
configured as an analog pin and skipped by the Digital Crossbar. Refer to Section “22. Port Input/Output”
on page 106 for the location of the VREF pin, as well as details of how to configure the pin in analog mode
and to be skipped by the crossbar.
REF0CN
VDD
R1
External
Voltage
Reference
Circuit
VREF
EN Temp Sensor
To Analog Mux
0
GND
+
4.7F
0.1F
Recommended Bypass
Capacitors
0
VDD
1
Internal
Regulator
1
REGOVR
VREF
(to ADC)
Figure 11.1. Voltage Reference Functional Block Diagram
Rev. 1.2
55
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