TMPR4956C datasheet(31/286 Pages) TOSHIBA

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Handling Precautions

3.3.9

Interfacing

When connecting devices with different input and output voltage levels, make sure that the input voltage

(VIL/VIH) and output voltage (VOL/VOH) levels match. Otherwise, the devices may malfunction. In addition,

when connecting devices with different power supply voltages, such as in a dual power supply system, device

breakdown may result if the power-on and power-off sequences are incorrect. For device interface details, refer

to the individual technical datasheets and databooks. In addition, if you have any questions about interfacing,

contact your nearest Toshiba office or distributor.

3.3.10

Decoupling

Spike currents generated during switching can cause power supply voltage and GND voltage levels to fluctuate,

causing ringing in the output waveform or a delay in the response speed. (The power supply and GND wiring

impedance is normally 50 to 100

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

high frequencies must be kept low. Specifically, this is ideally accomplished by routing thick and short power

supply and GND lines and by inserting decoupling capacitors (of approximately 0.01 to 1

µF) as high-frequency

filters between the power supply and GND into each required location on the circuit board.

For low-frequency filtering, it is appropriate to insert a 10 to 100

µF capacitor in each circuit board. However,

conversely if the capacitance is excessively large (such as 1000

µF), latch-up may result. An appropriate

capacitance value is therefore required.

On the other hand, in the case of high-speed logic ICs, noise is caused by reflection, crosstalk or common power

supply impedance. Reflections cause increased signal delay, ringing, overshoot and undershoot, thereby

reducing the device’s noise margin. One effective wiring measure for preventing reflections is to reduce the

wiring length by increasing the mounting density so as to lower the wiring inductance (L) and capacitance (C).

This measure, however, also requires consideration with regard to crosstalk between wires. In actual pattern

design, both of these factors must be considered.

3.3.11

External Noise

When externally induced noise or surges are applied to a printed circuit

board with long I/O signals or signal lines, malfunction may result,

depending on the device. To protect against noise, protective measures

against surges must be taken such as lowering the impedance of the

signal line or inserting a noise-canceling circuit.

For details of required protection, refer to individual technical datasheets and databooks.

Input/Output

Signals

TMPR4956C Datasheet(PDF) 31 Page - Toshiba Semiconductor