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PIC18F4431-I/PT 参数 Datasheet PDF下载

PIC18F4431-I/PT图片预览
型号: PIC18F4431-I/PT
PDF下载: 下载PDF文件 查看货源
内容描述: 28 /40/ 44引脚增强型闪存微控制器采用纳瓦技术,高性能PWM和A / D [28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D]
分类和应用: 闪存微控制器
文件页数/大小: 392 页 / 3127 K
品牌: MICROCHIP [ MICROCHIP ]
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PIC18F2331/2431/4331/4431  
FIGURE 2-3:  
SUGGESTED PLACEMENT  
OF THE OSCILLATOR  
CIRCUIT  
2.5  
External Oscillator Pins  
Many microcontrollers have options for at least two  
oscillators: a high-frequency primary oscillator and a  
low-frequency  
secondary  
oscillator  
(refer to  
Single-Sided and In-Line Layouts:  
Section 3.0 “Oscillator Configurations” for details).  
Copper Pour  
(tied to ground)  
Primary Oscillator  
Crystal  
The oscillator circuit should be placed on the same  
side of the board as the device. Place the oscillator  
circuit close to the respective oscillator pins with no  
more than 0.5 inch (12 mm) between the circuit  
components and the pins. The load capacitors should  
be placed next to the oscillator itself, on the same side  
of the board.  
DEVICE PINS  
Primary  
OSC1  
OSC2  
GND  
Oscillator  
C1  
C2  
`
`
Use a grounded copper pour around the oscillator cir-  
cuit to isolate it from surrounding circuits. The  
grounded copper pour should be routed directly to the  
MCU ground. Do not run any signal traces or power  
traces inside the ground pour. Also, if using a two-sided  
board, avoid any traces on the other side of the board  
where the crystal is placed.  
T1OSO  
T1OS I  
Timer1 Oscillator  
Crystal  
`
Layout suggestions are shown in Figure 2-4. In-line  
packages may be handled with a single-sided layout  
that completely encompasses the oscillator pins. With  
fine-pitch packages, it is not always possible to com-  
pletely surround the pins and components. A suitable  
solution is to tie the broken guard sections to a mirrored  
ground layer. In all cases, the guard trace(s) must be  
returned to ground.  
T1 Oscillator: C2  
T1 Oscillator: C1  
Fine-Pitch (Dual-Sided) Layouts:  
Top Layer Copper Pour  
(tied to ground)  
In planning the application’s routing and I/O assign-  
ments, ensure that adjacent port pins and other signals  
in close proximity to the oscillator are benign (i.e., free  
of high frequencies, short rise and fall times, and other  
similar noise).  
Bottom Layer  
Copper Pour  
(tied to ground)  
OSCO  
For additional information and design guidance on  
oscillator circuits, please refer to these Microchip  
Application Notes, available at the corporate web site  
(www.microchip.com):  
C2  
Oscillator  
Crystal  
GND  
AN826, Crystal Oscillator Basics and Crystal  
C1  
Selection for rfPIC™ and PICmicro® Devices”  
• AN849, “Basic PICmicro® Oscillator Design”  
OSCI  
• AN943, “Practical PICmicro® Oscillator Analysis  
and Design”  
• AN949, “Making Your Oscillator Work”  
DEVICE PINS  
2.6  
Unused I/Os  
Unused I/O pins should be configured as outputs and  
driven to a logic low state. Alternatively, connect a 1 kΩ  
to 10 kresistor to VSS on unused pins and drive the  
output to logic low.  
DS39616D-page 28  
2010 Microchip Technology Inc.  
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