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PIC18F24J10-I/SO 参数 Datasheet PDF下载

PIC18F24J10-I/SO图片预览
型号: PIC18F24J10-I/SO
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
文件页数/大小: 368 页 / 5652 K
品牌: MICROCHIP [ MICROCHIP ]
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PIC18F45J10 FAMILY  
FIGURE 20-1:  
COMPARATOR VOLTAGE REFERENCE BLOCK DIAGRAM  
CVRSS = 1  
CVRSS = 0  
VREF+  
VDD  
8R  
CVR<3:0>  
R
CVREN  
R
R
R
16 Steps  
CVREF  
R
R
R
CVRR  
VREF-  
8R  
CVRSS = 1  
CVRSS = 0  
20.2 Voltage Reference Accuracy/Error  
20.4 Effects of a Reset  
The full range of voltage reference cannot be realized  
due to the construction of the module. The transistors  
on the top and bottom of the resistor ladder network  
(Figure 20-1) keep CVREF from approaching the refer-  
ence source rails. The voltage reference is derived  
from the reference source; therefore, the CVREF output  
changes with fluctuations in that source. The tested  
absolute accuracy of the voltage reference can be  
found in Section 24.0 “Electrical Characteristics”.  
A device Reset disables the voltage reference by  
clearing bit, CVREN (CVRCON<7>). This Reset also  
disconnects the reference from the RA2 pin by clearing  
bit, CVROE (CVRCON<6>) and selects the high-voltage  
range by clearing bit, CVRR (CVRCON<5>). The CVR  
value select bits are also cleared.  
20.5 Connection Considerations  
The voltage reference module operates independently  
of the comparator module. The output of the reference  
generator may be connected to the RA2 pin if the  
CVROE bit is set. Enabling the voltage reference out-  
put onto RA2 when it is configured as a digital input will  
increase current consumption. Connecting RA2 as a  
digital output with CVRSS enabled will also increase  
current consumption.  
20.3 Operation During Sleep  
When the device wakes up from Sleep through an  
interrupt or a Watchdog Timer time-out, the contents of  
the CVRCON register are not affected. To minimize  
current consumption in Sleep mode, the voltage  
reference should be disabled.  
The RA2 pin can be used as a simple D/A output with  
limited drive capability. Due to the limited current drive  
capability, a buffer must be used on the voltage  
reference output for external connections to VREF.  
Figure 20-2 shows an example buffering technique.  
DS39682E-page 232  
© 2009 Microchip Technology Inc.