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3.3.13
Peripheral circuits
In most cases semiconductor devices are used with peripheral circuits and components. The input and output
signal voltages and currents in these circuits must be chosen to match the semiconductor device's specifications.
The following factors must be taken into account.
(1) Inappropriate voltages or currents applied to a device's input pins may cause it to operate erratically. Some
devices contain pull-up or pull-down resistors. When designing your system, remember to take the effect of
this on the voltage and current levels into account.
(2) The output pins on a device have a predetermined external circuit drive capability. If this drive capability is
greater than that required, either incorporate a compensating circuit into your design or carefully select
suitable components for use in external circuits.
3.3.14
Safety standards
Each country has safety standards which must be observed. These safety standards include requirements for
quality assurance systems and design of device insulation. Such requirements must be fully taken into account to
ensure that your design conforms to the applicable safety standards.
3.3.15
Other precautions
(1) When designing a system, be sure to incorporate fail-safe and other appropriate measures according to the
intended purpose of your system. Also, be sure to debug your system under actual board-mounted
conditions.
(2) If a plastic-package device is placed in a strong electric field, surface leakage may occur due to the charge-
up phenomenon, resulting in device malfunction. In such cases take appropriate measures to prevent this
problem, for example by protecting the package surface with a conductive shield.
(3) With some microcomputers and MOS memory devices, caution is required when powering on or resetting
the device. To ensure that your design does not violate device specifications, consult the relevant databook
for each constituent device.
(4) Ensure that no conductive material or object (such as a metal pin) can drop onto and short the leads of a
device mounted on a printed circuit board.
3.4
Inspection, Testing and Evaluation
3.4.1
Grounding
3 General Safety Precautions and Usage Considerations
Ground all measuring instruments, jigs, tools and soldering irons to earth.
Electrical leakage may cause a device to break down or may result in electric shock.
3-10
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