C8051F537-IT Silicon Laboratories Inc, C8051F537-IT Datasheet - Page 139

• Manufacturer Part Number: C8051F537-IT
• Description: IC 8051 MCU 2K FLASH 20TSSOP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F53xr

Specifications of C8051F537-IT

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 16
• Program Memory Size: 2KB (2K x 8)
• Program Memory Type: FLASH
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.25 V
• Data Converters: A/D 16x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 20-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Other names: 336-1401

Note: The load capacitance depends upon the crystal and the manufacturer. Please refer to the crystal
data sheet when completing these calculations.
The equation for determining the load capacitance for two capacitors is:
Where:
C
C
The stray capacitance for a typical layout where the crystal is as close as possible to the pins is 2–5 pF per
pin.
If C
For example, a tuning-fork crystal of 32 kHz with a recommended load capacitance of 12.5 pF should use
the configuration shown in Figure 14.1, Option 1. With a stray capacitance of 3 pF per pin (6 pF total), the
13 pF capacitors yield an equivalent capacitance of 12.5 pF across the crystal, as shown in Figure 14.2.
Important Note on External Crystals: Crystal oscillator circuits are quite sensitive to PCB layout. The
crystal should be placed as close as possible to the XTAL pins on the device. The traces should be as
short as possible and shielded with ground plane from any other traces which could introduce noise or
interference.
A
S
and C
is the total stray capacitance of the PCB.
A
and C
B
are the capacitors connected to the crystal leads.
B
are the same (C), then the equation becomes:
Figure 14.2. 32 kHz External Crystal Example
32 kHz
13 pF
13 pF
C8051F52x/F52xA/F53x/F53xA
C
L
C
=
L
Rev. 1.3
C
------------------- -
C
=
A
A

+
C
--- -
2
C
C
+
B
B
C
+
S
10 M
C
S

XTAL1
XTAL2
139