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SN8F2280 参数 Datasheet PDF下载

SN8F2280图片预览
型号: SN8F2280
PDF下载: 下载PDF文件 查看货源
内容描述: 8位微控制器 [8-Bit Micro-Controller]
分类和应用: 微控制器
文件页数/大小: 163 页 / 3660 K
品牌: SONIX [ SONIX TECHNOLOGY COMPANY ]
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SN8F2280 Series  
USB 2.0 Full-Speed 8-Bit Micro-Controller  
3.4.3 BROWN OUT RESET IMPROVEMENT  
How to improve the brown reset condition? There are some methods to improve brown out reset as following.  
z
z
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LVD reset  
Watchdog reset  
Reduce the system executing rate  
External reset circuit. (Zener diode reset circuit, Voltage bias reset circuit, External reset IC)  
’
Note:  
1.  
The “ Zener diode reset circuit”, “Voltage bias reset circuit” and “External reset IC” can  
completely improve the brown out reset, DC low battery and AC slow power down conditions.  
2. For AC power application and enhance EFT performance, the system clock is 4MHz/4 (1 mips)  
and use external reset (“ Zener diode reset circuit”, “Voltage bias reset circuit”, “External reset  
IC”). The structure can improve noise effective and get good EFT characteristic.  
LVD reset:  
VDD  
VSS  
LVD Detect Voltage  
Power  
Power is below LVD Detect  
Voltage and System Reset.  
System Normal Run  
System Stop  
System Status  
Power On  
Delay Time  
The LVD (low voltage detector) is built-in Sonix 8-bit MCU to be brown out reset protection. When the VDD drops and  
is below LVD detect voltage, the LVD would be triggered, and the system is reset. The LVD detect level is different by  
each MCU. The LVD voltage level is a point of voltage and not easy to cover all dead-band range. Using LVD to  
improve brown out reset is depend on application requirement and environment. If the power variation is very deep,  
violent and trigger the LVD, the LVD can be the protection. If the power variation can touch the LVD detect level and  
make system work error, the LVD can’t be the protection and need to other reset methods. More detail LVD information  
is in the electrical characteristic section.  
Watchdog reset:  
The watchdog timer is a protection to make sure the system executes well. Normally the watchdog timer would be clear  
at one point of program. Don’t clear the watchdog timer in several addresses. The system executes normally and the  
watchdog won’t reset system. When the system is under dead-band and the execution error, the watchdog timer can’t  
be clear by program. The watchdog is continuously counting until overflow occurrence. The overflow signal of  
watchdog timer triggers the system to reset, and the system return to normal mode after reset sequence. This method  
also can improve brown out reset condition and make sure the system to return normal mode.  
If the system reset by watchdog and the power is still in dead-band, the system reset sequence won’t be successful  
and the system stays in reset status until the power return to normal range.  
Reduce the system executing rate:  
If the system rate is fast and the dead-band exists, to reduce the system executing rate can improve the dead-band.  
The lower system rate is with lower minimum operating voltage. Select the power voltage that’s no dead-band issue  
and find out the mapping system rate. Adjust the system rate to the value and the system exits the dead-band issue.  
This way needs to modify whole program timing to fit the application requirement.  
External reset circuit:  
The external reset methods also can improve brown out reset and is the complete solution. There are three external  
reset circuits to improve brown out reset including “Zener diode reset circuit”, “Voltage bias reset circuit” and “External  
reset IC”. These three reset structures use external reset signal and control to make sure the MCU be reset under  
power dropping and under dead-band. The external reset information is described in the next section.  
SONiX TECHNOLOGY CO., LTD  
Page 47  
Version 1.1  
 
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