PIC12C508AT-04I/SN Microchip Technology, PIC12C508AT-04I/SN Datasheet - Page 37

• Manufacturer Part Number: PIC12C508AT-04I/SN
• Description: IC,MICROCONTROLLER,8-BIT,PIC CPU,CMOS,SOP,8PIN,PLASTIC
• Manufacturer: Microchip Technology
• Series: PIC® 12Cr

Specifications of PIC12C508AT-04I/SN

• Rohs Compliant: YES
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 4MHz
• Peripherals: POR, WDT
• Number Of I /o: 5
• Program Memory Size: 768B (512 x 12)
• Program Memory Type: OTP
• Ram Size: 25 x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 309-1046 - ADAPTER 8-SOIC TO 8-DIP309-1045 - ADAPTER 8-SOIC TO 8-DIPAC124001 - MODULE SKT PROMATEII 8DIP/SOIC
• Eeprom Size: -
• Data Converters: -
• Connectivity: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: PIC12C508AT-04ISN

8.2.3
Either a prepackaged oscillator or a simple oscillator
circuit with TTL gates can be used as an external
crystal oscillator circuit. Prepackaged oscillators
provide a wide operating range and better stability. A
well-designed crystal oscillator will provide good
performance with TTL gates. Two types of crystal
oscillator circuits can be used: one with parallel
resonance, or one with series resonance.
Figure 8-4
resonant oscillator circuit. The circuit is designed to
use the fundamental frequency of the crystal. The
74AS04 inverter performs the 180-degree phase shift
that a parallel oscillator requires. The 4.7 k
provides the negative feedback for stability. The 10 k
potentiometers bias the 74AS04 in the linear region.
This circuit could be used for external oscillator
designs.
FIGURE 8-4:
Figure 8-5 shows a series resonant oscillator circuit.
This circuit is also designed to use the fundamental
frequency of the crystal. The inverter performs a 180-
degree phase shift in a series resonant oscillator
circuit. The 330
feedback to bias the inverters in their linear region.
FIGURE 8-5:
1999 Microchip Technology Inc.
74AS04
330
10k
EXTERNAL CRYSTAL OSCILLATOR
CIRCUIT
+5V
shows
20 pF
0.1 F
10k
XTAL
74AS04
XTAL
4.7k
EXTERNAL PARALLEL
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
EXTERNAL SERIES
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
74AS04
330
implementation
resistors provide the negative
20 pF
10k
74AS04
74AS04
To Other
Devices
To Other
Devices
of
PIC12C5XX
PIC12C5XX
CLKIN
a
CLKIN
resistor
parallel
8.2.4
For timing insensitive applications, the RC device
option offers additional cost savings. The RC oscillator
frequency is a function of the supply voltage, the
resistor (Rext) and capacitor (Cext) values, and the
operating temperature. In addition to this, the oscillator
frequency will vary from unit to unit due to normal
process
difference in lead frame capacitance between package
types will also affect the oscillation frequency,
especially for low Cext values. The user also needs to
take into account variation due to tolerance of external
R and C components used.
Figure 8-6 shows how the R/C combination is
connected to the PIC12C5XX. For Rext values below
2.2 k , the oscillator operation may become unstable,
or stop completely. For very high Rext values
(e.g., 1 M ) the oscillator becomes sensitive to noise,
humidity and leakage. Thus, we recommend keeping
Rext between 3 k and 100 k .
Although the oscillator will operate with no external
capacitor (Cext = 0 pF), we recommend using values
above 20 pF for noise and stability reasons. With no or
small external capacitance, the oscillation frequency
can vary dramatically due to changes in external
capacitances, such as PCB trace capacitance or
package lead frame capacitance.
The Electrical Specifications sections show RC
frequency variation from part to part due to normal
process variation. The variation is larger for larger R
(since leakage current variation will affect RC
frequency more for large R) and for smaller C (since
variation of input capacitance will affect RC frequency
more).
Also, see the Electrical Specifications sections for
variation of oscillator frequency due to V
Rext/Cext values as well as frequency variation due to
operating temperature for given R, C, and V
FIGURE 8-6:
Cext
V
Rext
SS
V
DD
EXTERNAL RC OSCILLATOR
parameter
EXTERNAL RC OSCILLATOR
MODE
variation.
PIC12C5XX
OSC1
N
Furthermore,
DS40139E-page 37
PIC12C5XX
DD
DD
Internal
clock
for given
values.
the