C8051F709-GQR Silicon Labs, C8051F709-GQR Datasheet - Page 70

• 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

C8051F70x/71x
12.1. External Voltage References
To use an external voltage reference, REFSL[1:0] should be set to 00. Bypass capacitors should be added
as recommended by the manufacturer of the external voltage reference.
12.2. Internal Voltage Reference Options
A 1.6 V high-speed reference is included on-chip. The high speed internal reference is selected by setting
REFSL[1:0] to 11. When selected, the high-speed internal reference will be automatically enabled on an
as-needed basis by ADC0.
For applications with a non-varying power supply voltage, using the power supply as the voltage reference
can provide ADC0 with added dynamic range at the cost of reduced power supply noise rejection. To use
the 1.8 to 3.6 V power supply voltage (V
) or the 1.8 V regulated digital supply voltage as the reference
DD
source, REFSL[1:0] should be set to 01 or 10, respectively.
12.3. Analog Ground Reference
To prevent ground noise generated by switching digital logic from affecting sensitive analog measure-
ments, a separate analog ground reference option is available. When enabled, the ground reference for
ADC0 is taken from the P0.1/AGND pin. Any external sensors sampled by ADC0 should be referenced to
the P0.1/AGND pin. The separate analog ground reference option is enabled by setting REFGND to 1.
Note that when using this option, P0.1/AGND must be connected to the same potential as GND.
12.4. Temperature Sensor Enable
The TEMPE bit in register REF0CN enables the temperature sensor. While disabled, the temperature sen-
sor defaults to a high impedance state and any ADC0 measurements performed on the sensor result in
meaningless data.
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