Thermal Design <R; Deciding On Whether Particular Measures For Heat Dissipation Are Required; Estimating Tj; Estimating Power Consumption - Renesas R-IN32M3 Series User Manual

R-IN32M3 Series: Board design edition
25. Thermal Design
This section describes the thermal characteristics of the R-IN32M3, and includes notes that require attention in the design
of the board on which the device is mounted in terms of the dissipation of heat and the prevention of abnormal heating.
Since the R-IN32M3-EC incorporates an Ethernet PHY module, large-capacity memory, and a regulator, it requires
greater consideration of heat than most devices.
Design the board and casing in consideration of heat dissipation.
25.1

Deciding on whether Particular Measures for Heat Dissipation are Required

25.1.1

Estimating Tj

Take Tj ≤ 110°C as the criterion for Tj of the R-IN32M3. Estimate Tj from the following formulae.
Tj = Tt + Ψjt x power or Tj = Ta + θja x power
Tj
Tt
Ta
θja
Ψjt
Power
If Tj ≤ 110°C is satisfied, the semiconductor device does not require further measures for heat dissipation.
However, if the semiconductor device is to be installed in ways that have varying criteria for determining increases in
temperature, prepare measures for heat dissipation as required.
If Tj ≤ 110°C is not satisfied, heat dissipation solutions are necessary.
25.1.2

Estimating Power Consumption

For the 3.3-V sub-systems, estimate the power consumption from the value for current on the R-IN32M3 Series Data
Sheet.
Since it is temperature dependent, the power consumption of the 1.0-V sub-systems is estimated from the following
formula according to the operating temperature.
Power (1.0-V sub-systems) = 140 + 103 × e
The list in 25.1.4, Results of Estimating Power Consumption of the 1-V Sub-Systems at Tj, gives results of estimation
under specific conditions.
R18UZ0021EJ0400
Dec. 28, 2018
<R>
: Junction temperature [°C]
: Package surface temperature [°C]
: Ambient temperature [°C]
: Thermal resistance [°C/W] between the junction (at temperature Tj) and the ambient
environment (at Ta)
(See section 25.1.3, Thermal Resistances under the JEDEC Conditions (for θja and
Ψjt).)
: Thermal resistance [°C/W] between the junction (at temperature Tj) and the surface of
the package (at Tt)
(See section 25.1.3, Thermal Resistances under the JEDEC Conditions (for θja and
Ψjt).)
: Power consumption [W]
(1.0-V sub-systems + 3.3-V sub-systems; that for the 1.5-V sub-systems must also be
added when the internal regulator is not in use)
(0.0179 × Tj)
[mW]
25. Thermal Design <R>
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