C8051F330DR Silicon Labs, C8051F330DR Datasheet - Page 116

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C8051F330DR

Manufacturer Part Number
C8051F330DR
Description
8-bit Microcontrollers - MCU 8kB 10ADC
Manufacturer
Silicon Labs
Datasheet

Specifications of C8051F330DR

Product Category
8-bit Microcontrollers - MCU
Core
8051
Data Bus Width
8 bit
Maximum Clock Frequency
25 MHz
Program Memory Size
8 KB
Data Ram Size
768 B
On-chip Adc
No
Operating Supply Voltage
2.7 V to 3.6 V
Package / Case
QFN-20
Mounting Style
SMD/SMT
Data Rom Size
128 B
Interface Type
I2C, SPI, UART
Maximum Operating Temperature
+ 85 C
Minimum Operating Temperature
- 40 C
Number Of Programmable I/os
17
Number Of Timers
4
On-chip Dac
No
Processor Series
C8051
Program Memory Type
Flash
Factory Pack Quantity
1500
Supply Voltage - Max
3.6 V
Supply Voltage - Min
2.7 V
C8051F330/1/2/3/4/5
13.3.2. External RC Example
If an RC network is used as an external oscillator source for the MCU, the circuit should be configured as
shown in Figure 13.1, Option 2. The capacitor should be no greater than 100 pF; however for very small
capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. To deter-
mine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, first
select the RC network value to produce the desired frequency of oscillation. If the frequency desired is
100 kHz, let R = 246 k and C = 50 pF:
3
3
f = 1.23( 10
) / RC = 1.23 ( 10
) / [ 246 x 50 ] = 0.1 MHz = 100 kHz
Referring to the table in SFR Definition 13.4, the required XFCN setting is 010b.
13.3.3. External Capacitor Example
If a capacitor is used as an external oscillator for the MCU, the circuit should be configured as shown in
Figure 13.1, Option 3. The capacitor should be no greater than 100 pF; however for very small capacitors,
the total capacitance may be dominated by parasitic capacitance in the PCB layout. To determine the
required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, select the capaci-
tor to be used and find the frequency of oscillation from the equations below. Assume V
= 3.0 V and
DD
f = 150 kHz:
f = KF / (C x VDD)
0.150 MHz = KF / (C x 3.0)
Since the frequency of roughly 150 kHz is desired, select the K Factor from the table in SFR Definition 13.4
(OSCXCN) as KF = 22:
0.150 MHz = 22 / (C x 3.0)
C x 3.0 = 22 / 0.150 MHz
C = 146.6 / 3.0 pF = 48.8 pF
Therefore, the XFCN value to use in this example is 011b and C = 50 pF.
120
Rev. 1.7

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