D79F9211 Microcontrollers Datasheet pdf - Single-Chip Microcontrollers. Equivalent, Catalog

NOTES FOR CMOS DEVICES

1 VOLTAGE APPLICATION WAVEFORM AT INPUT PIN

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 VIL (MAX) and VIH (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 VIL (MAX) and

VIH (MIN).

2 HANDLING OF UNUSED INPUT PINS

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 VDD 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.

3 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.

4 STATUS BEFORE INITIALIZATION

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.

5 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.

6 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.

Preliminary User’s Manual

Single-Chip Microcontrollers. D79F9211 Datasheet