TMP93CS41DF datasheet(38/48 Pages) TOSHIBA

38 / 48 page

Quality and Reliability Assurance / Handling Precautions

030901

QUA-38

2002-02-20

4.3.9

Interfacing

When connecting inputs and outputs between devices, make sure input

voltage (VIL/VIH) and output voltage (VOL/VOH) levels are matched. Otherwise,

the devices may malfunction. When connecting devices operating at different

supply voltages, such as in a dual-power-supply system, be aware that

erroneous power-on and power-off sequences can result in device breakdown.

For details of how to interface particular devices, consult the relevant

technical datasheets and databooks. If you have any questions or doubts about

interfacing, contact your nearest Toshiba office or distributor.

4.3.10 Decoupling

Spike currents generated during switching can cause Vcc (Vdd) and GND

(Vss) voltage levels to fluctuate, causing ringing in the output waveform or a

delay in response speed. (The power supply and GND wiring impedance is

normally 50

Ω to 100 Ω.) For this reason, the impedance of power supply lines

with respect to high frequencies must be kept low. This can be accomplished

by using thick and short wiring for the Vcc (Vdd) and GND (Vss) lines and by

installing decoupling capacitors (of approximately 0.01 to 1

µF capacitance) as

high-frequency filters between Vcc (Vdd) and GND (Vss) at strategic locations

on the printed circuit board.

For low-frequency filtering, it is a good idea to install a 10- to 100-

µF capacitor

on the printed circuit board (one capacitor will suffice). If the capacitance is

excessively large, however, (e.g. several thousand

µF) latch-up can be a

problem. Be sure to choose an appropriate capacitance value.

An important point about wiring is that, in the case of high-speed logic ICs,

noise is caused mainly by reflection and crosstalk, or by the power supply

impedance. Reflections cause increased signal delay, ringing, overshoot and

undershoot, thereby reducing the device’s safety margins with respect to noise.

To prevent reflections, reduce the wiring length by increasing the device

mounting density so as to lower the inductance (L) and capacitance (C) in the

wiring. Extreme care must be taken, however, when taking this corrective

measure, since it tends to cause crosstalk between the wires. In practice, there

must be a trade-off between these two factors.

4.3.11 External Noise

Printed circuit boards with long I/O or signal

pattern lines are vulnerable to induced noise or

surges from outside sources. Consequently,

malfunctions or breakdowns can result from

overcurrent or overvoltage, depending on the

types of device used. To protect against noise,

lower the impedance of the pattern line or insert

a noise-canceling circuit. Protective measures

must also be taken against surges.

For details of the appropriate protective measures for a particular device,

consult the relevant databook.

TMP93CS41DF 数据表(PDF) 38 Page - Toshiba Semiconductor

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