TMP93CS41DF datasheet(37/48 Pages) TOSHIBA

37 / 48 page

Quality and Reliability Assurance / Handling Precautions

030901

QUA-37

2002-02-20

4.3.7

Load Capacitance

Some devices display increased delay times if the load capacitance is large. Also,

large charging and discharging currents will flow in the device, causing noise.

Furthermore, since outputs are shorted for a relatively long time, wiring can

become fused.

Consult the technical information for the device being used to determine the

recommended load capacitance.

4.3.8

Thermal Design

The failure rate of semiconductor devices is greatly increased as operating

temperatures increase. As shown in Figure 4.2, the internal thermal stress on a

device is the sum of the ambient temperature and the temperature rise due to

power dissipation in the device. Therefore, to achieve optimum reliability, observe

the following precautions concerning thermal design:

(1)

Keep the ambient temperature (Ta) as low as possible.

(2)

If the device’s dynamic power dissipation is relatively large, select the

most appropriate circuit board material, and consider the use of heat

sinks or of forced air cooling. Such measures will help lower the thermal

resistance of the package.

(3)

Derate the device’s absolute maximum ratings to minimize thermal stress

from power dissipation.

θja = θjc + θca

θja = (Tj – Ta)/P

θjc = (Tj – Tc)/P

θca = (Tc – Ta)/P

in which

θja = thermal resistance between junction and surrounding air (°C/W)

θjc = thermal resistance between junction and package surface, or

internal thermal resistance (°C/W)

θca = thermal resistance between package surface and

surrounding air, or external thermal resistance (°C/W)

Tj = junction temperature or chip temperature (°C)

Tc = package surface temperature or case temperature (°C)

Ta = ambient temperature (°C)

= power dissipation (W)

θca

θjc

Figure 4.2 Thermal Resistance of Package

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