參數(shù)資料
型號： PIC16LC662T-04/L
元件分類： 微控制器/微處理器
英文描述： 8-BIT, OTPROM, 4 MHz, RISC MICROCONTROLLER, PQCC44
封裝： PLASTIC, LCC-44
文件頁數(shù)： 91/136頁
文件大?。?/td> 634K
代理商： PIC16LC662T-04/L
PIC16C64X & PIC16C66X
DS30559A-page 58
Preliminary
1996 Microchip Technology Inc.
9.2.3
EXTERNAL CRYSTAL OSCILLATOR
CIRCUIT
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 9-4 shows implementation of a parallel resonant
oscillator circuit. The circuit is designed to use the fun-
damental frequency of the crystal. The 74AS04 inverter
performs the 180-degree phase shift that a parallel
oscillator requires. The 4.7 k
resistor provides the
negative feedback for stability. The 10 k
potentiome-
ter biases the 74AS04 in the linear region. This could
be used for external oscillator designs.
FIGURE 9-4:
EXTERNAL PARALLEL
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
Figure 9-5 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 9-5:
EXTERNAL SERIES
RESONANT CRYSTAL
OSCILLATOR CIRCUIT
20 pF
+5V
20 pF
10k
4.7k
10k
74AS04
XTAL
10k
74AS04
CLKIN
To Other
Devices
PIC16CXXX
330 k
74AS04
PIC16CXXX
CLKIN
To Other
Devices
XTAL
330 k
74AS04
0.1
F
9.2.4
RC OSCILLATOR
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 (Rext) and capacitor (Cext) values, and the operat-
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
Cext values. The user also needs to take into account
variation due to tolerance of external R and C compo-
nents used. Figure 9-6 shows how the R/C combina-
tion is connected to the PIC16CXXX. 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 to keep
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 pack-
age lead frame capacitance.
See characterization data for desired device for RC fre-
quency variation from part to part due to normal pro-
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 VDD for given Rext/
Cext values as well as frequency variation due to oper-
ating temperature for given R, C, and VDD values.
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 9-6:
RC OSCILLATOR MODE
OSC2/CLKOUT
Cext
VDD
Rext
VSS
PIC16CXXX
OSC1
Fosc/4
Internal
clock
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
PIC16LC66T-04/SO 功能描述:8位微控制器 -MCU 14KB 368 RAM 22 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
PIC16LC66T-04I/SO 功能描述:8位微控制器 -MCU 14KB 368 RAM 22 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
PIC16LC67-04/L 功能描述:8位微控制器 -MCU 14KB 368 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
PIC16LC67-04/P 功能描述:8位微控制器 -MCU 14KB 368 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
PIC16LC67-04/PQ 功能描述:8位微控制器 -MCU 14KB 368 RAM 33 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
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