Справочник Пользователя для IBM EM78P447N

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Any microcontroller is not guaranteed to start and operate properly before the power 
supply stays at its steady state.  EM78P447N is equipped with Power On Voltage 
Detector(POVD) with a detecting level is 2.0V.  It will work well if Vdd rises fast enough 
(10 ms or less).  In many critical applications, however, extra devices are still required 
to assist in solving power-up problems. 

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.