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EM78156EAS 参数 Datasheet PDF下载

EM78156EAS图片预览
型号: EM78156EAS
PDF下载: 下载PDF文件 查看货源
内容描述: 8位微控制器与MASK ROM [8-Bit Microcontroller with MASK ROM]
分类和应用: 微控制器光电二极管局域网有原始数据的样本ROM
文件页数/大小: 48 页 / 420 K
品牌: ELAN [ ELAN MICROELECTRONICS CORP ]
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EM78156E  
8-Bit Microcontroller with MASK ROM  
extra external reset circuit will work well if Vdd can rise at very fast speed (50 ms or  
less). However, under most cases where critical applications are involved, extra  
devices are required to assist in solving the power-up problems.  
4.10 External Power On Reset Circuit  
The circuit shown in Fig.16 implements an external RC to produce the reset pulse. The  
pulse width (time constant) should be kept long enough for Vdd to reached minimum  
operation voltage. This circuit is used when the power supply has slow rise time.  
Because the current leakage from the /RESET pin is about ±5µA, it is recommended  
that R should not be greater than 40 K. In this way, the /RESET pin voltage is held  
below 0.2V. The diode (D) acts as a short circuit at the moment of power down. The  
capacitor C will discharge rapidly and fully. Rin, the current-limited resistor, will prevent  
high current or ESD (electrostatic discharge) from flowing to pin /RESET.  
Vdd  
R
/RESET  
D
EM78156E  
Rin  
C
Fig. 14 External Power-Up Reset Circuit  
4.11 Residue-Voltage Protection  
When battery is replaced, device power (Vdd) is taken off but residue-voltage remains.  
The residue-voltage may trips below Vdd minimum, but not to zero. This condition may  
cause a poor power on reset. Fig.17 and Fig.18 show how to build a residue-voltage  
protection circuit.  
Vdd  
Vdd  
33K  
EM78156E  
/RESET  
Q1  
10K  
40K  
1N4684  
Fig. 15 Circuit 1 for the Residue Voltage Protection  
26 •  
Product Specification (V1.3) 07.29.2004  
(This specification is subject to change without further notice)  
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