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PIC18F25J10-I/SS 参数 Datasheet PDF下载

PIC18F25J10-I/SS图片预览
型号: PIC18F25J10-I/SS
PDF下载: 下载PDF文件 查看货源
内容描述: 28 /40/ 44引脚高性能, RISC微控制器 [28/40/44-Pin High-Performance, RISC Microcontrollers]
分类和应用: 微控制器和处理器外围集成电路光电二极管PC时钟
文件页数/大小: 368 页 / 5652 K
品牌: MICROCHIP [ MICROCHIP ]
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PIC18F45J10 FAMILY  
FIGURE 2-4:  
SUGGESTED PLACEMENT  
OF THE OSCILLATOR  
CIRCUIT  
2.6  
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  
Section 3.0 “Oscillator Configurations” for details).  
Main Oscillator  
Guard Ring  
13  
14  
15  
16  
17  
18  
19  
20  
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.  
Guard Trace  
Secondary  
Oscillator  
Use a grounded copper pour around the oscillator  
circuit 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. A suggested  
layout is shown in Figure 2-4.  
2.7  
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.  
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):  
AN826, Crystal Oscillator Basics and Crystal  
Selection for rfPIC™ and PICmicro® Devices”  
AN849, “Basic PICmicro® Oscillator Design”  
• AN943, “Practical PICmicro® Oscillator Analysis  
and Design”  
AN949, “Making Your Oscillator Work”  
DS39682E-page 26  
© 2009 Microchip Technology Inc.  
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