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Absolute Maximum Ratings (Temperature Characteristics)

Operating Temperature Range

The operating temperature range is a range that ensures normal operation and where expected IC functions are maintained.
Some IC characteristics vary based on temperature.
Therefore, unless otherwise specified, the values stipulated at 25C cannot be guaranteed.
There is a parameter that guarantees stable operation throughout the entire temperature range.
IC characteristics fluctuations within the operating temperature range are taken into account.

Maximum Junction Temperature/Storage Temperature Range

The maximum junction temperature is the maximum temperature the semiconductor can operate. Here, 'junction' refers to a PN junction.
If the chip temperature exceeds the maximum rated junction temperature, electron-hole pairs will be generated in the semiconductor crystal, preventing normal operation.
Therefore, thermal designs must take into account heat generation due to power consumption and ambient temperatures.
The maximum junction temperature is determined by production processes.
The storage temperature range denotes the maximum temperature during storage, when the IC is not in operation and no power is being consumed.
Normally this is equivalent to the maximum junction temperature.

Permissible Loss (Total Loss)

Permissible loss (total loss) indicates the power that the IC can consume at an ambient temperature Ta=25°C. When the IC consumes power, heat is generated, and the chip temperature will become higher than the ambient temperature.
The allowable chip temperature is determined by the maximum junction temperature, with permissible power consumption limited by the derating curves.
The internal IC chip determines the permissible loss at 25°C based on allowable temperature (maximum junction temperature) and thermal resistance of the package (heat dissipation characteristics)
The maximum junction temperature is also affected by production processes.

Heat generated from IC power consumption is dissipated by the package mold resin, lead frame, and other components.
The parameter that indicates heat dissipation characteristics is referred to as thermal resistance, and is represented by θj-a[℃/W].
This thermal resistance makes it possible to estimate the internal IC temperature.
An example of package thermal resistance is shown below. θj-a is determined by the sum of the thermal resistance θj-c between the chip and case (package) and the case and external (ambient) environment θc-a.
With a thermal resistance θj-a, ambient temperature Ta, power consumption P, the junction temperature can be calculated by the following equation.

Tj = Ta + θj-a × P [W]

Below shows the thermal derating curves.
These curves indicate the amount of power that can be consumed by the IC at different ambient temperatures without exceeding the permissible chip temperature.
As an example, let's consider the chip temperature of MSOP8.
Since the IC's storage temperature range is 55°C to 150°C, the maximum permissible chip temperature is 150°C. With a thermal resistance for MSOP8 of θj-a≒212.8℃/W, and an IC power consumption of 0.58mW, the junction temperature will be

Tj = 25[℃] + 212.8[℃/W] × 0.58[W] ≒ 150[℃]

Once the maximum permissible chip temperature is reached, no more power can be consumed. The reduced value per 1°C of the derating curves is determined from the reciprocal of the thermal resistance.
Here we show the thermal resistance of different package types. SOP8: 5.5mW/°C, SSOP-B8: 5.0mW/°C, MSOP8: 4.7mW/°C

Example of Thermal Derating Curves

Junction-External (Ambient) Thermal Resistance : θj-a=θj-c+θc-a[℃/W]
Where θj-c is the thermal resistance between the junction and case.
θc-a : Thermal Resistance Between Case and External 
Ta : Ambient Temperature
Tj : Junction Temperature
The slope of the derating curve is the reciprocal of θj-a

Package Thermal Resistance
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