C8051F351 Silicon Laboratories Inc, C8051F351 Datasheet - Page 67

• Manufacturer Part Number: C8051F351
• Description: IC 8051 MCU 8K FLASH 28MLP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F35xr

Specifications of C8051F351

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 50MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: POR, PWM, Temp Sensor, WDT
• Number Of I /o: 17
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Data Converters: A/D 8x24b; D/A 2x8b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-VQFN Exposed Pad, 28-HVQFN, 28-SQFN, 28-DHVQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

7.
There are two voltage reference options for the C8051F350/1/2/3 ADCs: the internal 2.5 V reference volt-
age, or an external reference voltage (see Figure 7.1). The AD0VREF bit in the ADC0CF register selects
the reference source.
The internal voltage reference circuit consists of a 1.25 V, temperature stable bandgap voltage reference
generator and a gain-of-two output buffer amplifier, to produce a 2.5 V voltage reference. When the inter-
nal voltage reference is used, it is driven out on the VREF+ pin, and the VREF- pin is connected to AGND.
The internal voltage reference is enabled by setting the AD0EN bit in register ADC0MD to ‘1’ and clearing
the AD0VREF bit in register ADC0CF to ‘0’ (See
(ADC0)” on page
given in Table 7.1.
The internal oscillator bias generator is automatically enabled whenever the internal oscillator is enabled.
For power requirement characterization, the BIASE bit in register REF0CN can also be used to enable the
internal oscillator bias generator, when the oscillator itself is not enabled. Likewise, the REFBE bit in regis-
ter REF0CN can be used to enable the internal bandgap generator, which is used by the ADC, the IDACs,
the Clock Multiplier, and the internal Voltage Reference. The internal reference bias generator is automati-
cally enabled whenever a peripheral requires it. See Figure 7.2 for the REF0CN register description.
Reference
(Optional)
External
Voltage
Voltage Reference
(Recommended)
Capacitors
Bypass
+
39). Electrical specifications for the internal voltage reference and bias generators are
Figure 7.1. Reference Circuitry Block Diagram
VREF+
VREF-
REFBE
BIASE
AD0VREF
AD0EN
IOSCEN
IDA0EN
IDA1EN
MULEN
AD0EN
Rev. 0.4
Section “5. 24 or 16-Bit Analog to Digital Converter
VREF to ADC
EN
EN
AGND
C8051F350/1/2/3
EN
Bias Generator
Oscillator Bias
Reference
Reference
Generator
Internal
Internal
Buffer
2.5V
To Internal
Oscillator
To ADC, IDACs,
Clock Multiplier
67