C8051F902-GU Silicon Laboratories Inc, C8051F902-GU Datasheet - Page 180

• Manufacturer Part Number: C8051F902-GU
• Description: IC MCU 8BIT 8KB FLASH 24QSOP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F9xxr

Specifications of C8051F902-GU

• Program Memory Type: FLASH
• Program Memory Size: 8KB (8K x 8)
• Package / Case: 24-QSOP
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 16
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 0.9 V ~ 3.6 V
• Data Converters: A/D 15x10/12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Processor Series: C8051F9x
• Core: 8051
• Data Ram Size: 768 B
• Interface Type: UART
• Maximum Clock Frequency: 25 MHz
• Number Of Timers: 4
• Operating Supply Voltage: 0.9 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: C8051F912DK
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 12 bit
• Package: 24QSOP
• Device Core: 8051
• Family Name: C8051F90x
• Maximum Speed: 25 MHz
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 16
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1849-5

C8051F91x-C8051F90x
19.1. Programmable Precision Internal Oscillator
All C8051F91x-C8051F90x devices include a programmable precision internal oscillator that may be
selected as the system clock. OSCICL is factory calibrated to obtain a 24.5 MHz frequency. See Section
“4. Electrical Characteristics” on page 36 for complete oscillator specifications.
The precision oscillator supports a spread spectrum mode which modulates the output frequency in order
to reduce the EMI generated by the system. When enabled (SSE = 1), the oscillator output frequency is
modulated by a stepped triangle wave whose frequency is equal to the oscillator frequency divided by 384
(63.8 kHz using the factory calibration). The deviation from the nominal oscillator frequency is +0%, –1.6%,
and the step size is typically 0.26% of the nominal frequency. When using this mode, the typical average
oscillator frequency is lowered from 24.5 MHz to 24.3 MHz.
19.2. Low Power Internal Oscillator
All C8051F91x-C8051F90x devices include a low power internal oscillator that defaults as the system
clock after a system reset. The low power internal oscillator frequency is 20 MHz ± 10% and is automati-
cally enabled when selected as the system clock and disabled when not in use. See Section “4. Electrical
Characteristics” on page 36 for complete oscillator specifications.
19.3. External Oscillator Drive Circuit
All C8051F91x-C8051F90x devices include an external oscillator circuit that may drive an external crystal,
ceramic resonator, capacitor, or RC network. A CMOS clock may also provide a clock input. Figure 19.1
shows a block diagram of the four external oscillator options. The external oscillator is enabled and config-
ured using the OSCXCN register.
The external oscillator output may be selected as the system clock or used to clock some of the digital
peripherals (e.g. Timers, PCA, etc.). See the data sheet chapters for each digital peripheral for details. See
Section “4. Electrical Characteristics” on page 36 for complete oscillator specifications.
19.3.1. External Crystal Mode
If a crystal or ceramic resonator is used as the external oscillator, the crystal/resonator and a 10 Mresis-
tor must be wired across the XTAL1 and XTAL2 pins as shown in Figure 19.1, Option 1. Appropriate load-
ing capacitors should be added to XTAL1 and XTAL2, and both pins should be configured for analog I/O
with the digital output drivers disabled.
Figure 19.2 shows the external oscillator circuit for a 20 MHz quartz crystal with a manufacturer recom-
mended load capacitance of 12.5 pF. Loading capacitors are "in series" as seen by the crystal and "in par-
allel" with the stray capacitance of the XTAL1 and XTAL2 pins. The total value of the each loading
capacitor and the stray capacitance of each XTAL pin should equal 12.5pF x 2 = 25 pF. With a stray capac-
itance of 10 pF per pin, the 15 pF capacitors yield an equivalent series capacitance of 12.5 pF across the
crystal.
Note: The recommended load capacitance depends upon the crystal and the manufacturer. Please refer to the crystal
data sheet when completing these calculations.
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