PIC16LC923-04/PT Microchip Technology, PIC16LC923-04/PT Datasheet - Page 105

• Manufacturer Part Number: PIC16LC923-04/PT
• Description: IC MCU OTP 4KX14 LCD DVR 64TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 16Cr

Specifications of PIC16LC923-04/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 4MHz
• Connectivity: I²C, SPI
• Peripherals: LCD, POR, PWM, WDT
• Number Of I /o: 25
• Program Memory Size: 7KB (4K x 14)
• Program Memory Type: OTP
• Ram Size: 176 x 8
• Voltage - Supply (vcc/vdd): 2.5 V ~ 6 V
• Oscillator Type: External
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 64-TFQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Data Converters: -

14.2.3
Either a prepackaged oscillator can be used or a simple
oscillator circuit with TTL gates can be built. Prepack-
aged 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 series
resonance, or one with parallel resonance.
Figure 14-4 shows implementation of a parallel reso-
nant 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 par-
allel oscillator requires. The 4.7 k resistor provides the
negative feedback for stability. The 10 k potentiometer
biases the 74AS04 in the linear region. This could be
used for external oscillator designs.
FIGURE 14-4: EXTERNAL PARALLEL
Figure 14-5 shows a series resonant oscillator circuit.
This circuit is also designed to use the fundamental fre-
quency of the crystal. The inverter performs a
180-degree phase shift in a series resonant oscillator
circuit. The 330 k resistors provide the negative feed-
back to bias the inverters in their linear region.
FIGURE 14-5: EXTERNAL SERIES
1997 Microchip Technology Inc.
74AS04
330 k
10k
EXTERNAL CRYSTAL OSCILLATOR
CIRCUIT
+5V
0.1 F
20 pF
XTAL
10k
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
74AS04
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
XTAL
4.7k
74AS04
330 k
20 pF
10k
74AS04
74AS04
To Other
Devices
To Other
Devices
PIC16CXXX
PIC16CXXX
CLKIN
CLKIN
14.2.4
For timing insensitive applications the “RC” device
option offers additional cost savings. The RC oscillator
frequency is a function of the supply voltage, the resis-
tor (R
ing temperature. In addition to this, the oscillator
frequency will vary from unit to unit due to normal pro-
cess parameter variation. Furthermore, the difference
in lead frame capacitance between package types will
also affect the oscillation frequency, especially for low
C
variation due to tolerance of external R and C compo-
nents used. Figure 14-6 shows how the R/C combina-
tion is connected to the PIC16CXXX. For R
below 2.2 k , the oscillator operation may become
unstable, or stop completely. For very high R
(e.g. 1 M ), the oscillator becomes sensitive to noise,
humidity and leakage. Thus, we recommend to keep
Rext between 3 k and 100 k .
Although the oscillator will operate with no external
capacitor (C
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 pack-
age lead frame capacitance.
See characterization data for desired device for RC fre-
quency variation from part to part due to normal pro-
R
operating temperature for given R, C, and V
The oscillator frequency, divided by 4, is available on
the OSC2/CLKOUT pin, and can be used for test pur-
poses or to synchronize other logic (see Figure 3-3 for
waveform).
FIGURE 14-6: RC OSCILLATOR MODE
cess 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).
See characterization data for desired device for varia-
tion of oscillator frequency due to V
EXT
EXT
C
R
V
EXT
SS
EXT
/C
EXT
values. The user also needs to take into account
V
EXT
DD
RC OSCILLATOR
) and capacitor (C
values as well as frequency variation due to
EXT
Fosc/4
= 0 pF), we recommend using values
OSC1
OSC2/CLKOUT
PIC16C9XX
EXT
) values, and the operat-
DS30444E - page 105
DD
PIC16CXXX
Internal
DD
EXT
EXT
clock
for given
values.
values
values