NEC PD789489 Manuale Utente

User’s Manual  U15331EJ4V1UD

Waveform distortion due to input noise or a reflected wave may cause malfunction.  If the input of the 

CMOS device stays in the area between V

IL

 (MAX) and V

IH

 (MIN) due to noise, etc., the device may 

malfunction.  Take care to prevent chattering noise from entering the device when the input level is fixed, 

and also in the transition period when the input level passes through the area between V

IL

 (MAX) and 

V

IH

 (MIN).

Unconnected CMOS device inputs can be cause of malfunction.  If an input pin is unconnected, it is 

possible that an internal input level may be generated due to noise, etc., causing malfunction.  CMOS 

devices behave differently than Bipolar or NMOS devices. Input levels of CMOS devices must be fixed 

high or low by using pull-up or pull-down circuitry.  Each unused pin should be connected to V

DD

 or GND 

via a resistor if there is a possibility that it will be an output pin.  All handling related to unused pins must 

be judged separately for each device and according to related specifications governing the device.

PRECAUTION AGAINST ESD 

A strong electric field, when exposed to a MOS device, can cause destruction of the gate oxide and 

ultimately degrade the device operation.  Steps must be taken to stop generation of static electricity as 

much as possible, and quickly dissipate it when it has occurred.  Environmental control must be 

adequate. When it is dry, a humidifier should be used.  It is recommended to avoid using insulators that 

easily build up static electricity.  Semiconductor devices must be stored and transported in an anti-static 

container, static shielding bag or conductive material.  All test and measurement tools including work 

benches and floors should be grounded.  The operator should be grounded using a wrist strap. 

Semiconductor devices must not be touched with bare hands.  Similar precautions need to be taken for 

PW boards with mounted semiconductor devices.

Power-on does not necessarily define the initial status of a MOS device.  Immediately after the power 

source is turned ON, devices with reset functions have not yet been initialized.  Hence, power-on does 

not guarantee output pin levels, I/O settings or contents of registers.  A device is not initialized until the 

reset signal is received.  A reset operation must be executed immediately after power-on for devices 

with reset functions.

POWER ON/OFF SEQUENCE 

In the case of a device that uses different power supplies for the internal operation and external 

interface, as a rule, switch on the external power supply after switching on the internal power supply. 

When switching the power supply off, as a rule, switch off the external power supply and then the 

internal power supply. Use of the reverse power on/off sequences may result in the application of an 

overvoltage to the internal elements of the device, causing malfunction and degradation of internal 

elements due to the passage of an abnormal current. 

The correct power on/off sequence must be judged separately for each device and according to related 

specifications governing the device. 

INPUT OF SIGNAL DURING POWER OFF STATE 

Do not input signals or an I/O pull-up power supply while the device is not powered.  The current 

injection that results from input of such a signal or I/O pull-up power supply may cause malfunction and 

the abnormal current that passes in the device at this time may cause degradation of internal elements.

Input of signals during the power off state must be judged separately for each device and according to 

related specifications governing the device.