Application Note

R01AN5624EJ0100 Rev.1.00 Page 1 of 8

Nov.25.20

RA4M3 Group

Notes on RA4M3 Group High-Temperature Operation

Introduction

Renesas provides RA4M3 Group microcontrollers that operate in high-temperature environments. These

products are guaranteed to operate within the stipulated range. However, the reliability of a semiconductor

device is influenced greatly by the environment in which it is used. That is, even for products with the same

quality level, if one is operated in a more severe environment, its reliability will be reduced. Conversely, if one

is used in a less severe environment, its reliability will increase. For example, a device used under extremely

severe conditions, such as those used for lifetime testing, may exhibit wear-out failures, even if the

environment is within the maximum ratings.

This application note presents notes on operating environments under which RA4M3 Group microcontrollers

are used in high-temperature applications.

Target Device

RA4M3 Group

Contents

1. Relationship between Actual Usage Environments for RA4M3 Group Microcontrollers and

Reliability ................................................................................................................................. 2

1.1 Approaches to microcontroller reliability.................................................................................................. 2

1.2 Derating ................................................................................................................................................... 2

2. Thermal Characteristics Term Definitions ................................................................................ 3

3. Thermal Characteristics ........................................................................................................... 4

3.1 RA4M3 Group thermal resistances ......................................................................................................... 4

4. Derating Examples for Representative High-Temperature Applications ................................... 5

5. Reference Documents ............................................................................................................. 7

Revision His tory .............................................................................................................................. 8

RA4M3 Group Notes on RA4M3 Group High-Te mper a tur e O per at ion

R01AN5624EJ0100 Rev.1.00 Page 2 of 8

Nov.25.20

1. Relationshi p between Actual Usage Environments for RA4M3 Group

Microcontrollers and Reliability

1.1 Approaches to microcontroller reliability

We strongly recommend that customers follow the items described in this document to assure device

reliability when using RA4M3 Group microcontrollers.

Semiconductor device reliability is indicated by the failure rate curve (bathtub curve). This curve is divided

into three regions:

• The early failure region, in which failures occur at a relatively early time after device use (operation) is first

started.

• The random failure period, during which, after the early failure period, failures occur randomly across the

relatively long period during which the device is used,

• The wear-out failure period (end of service life), during which failures increase with the elapsing of the

time that is inherent life of the device. (See the Reliability Handbook, Revision 2.50 (R51ZZ0001EJ0250)

for further details on the bathtub curve.)

Of these regions, it is the wear-out failure region that is most strongly influenced by the thermal environment

in which the semiconductor device is used. The concept of derating is critical to assuring that RA4M3 Group

microcontrollers do not reach the wear-out failure region.

1.2 Derating

Derating is defined under JIS Z 8115 as the systematic reduction of load for the sake of improved reliability.

Derating is commonly applied to product groups, such as discreet components and power ICs, where

concern is required regarding the junction temperature due to the relationship between the generated power,

ambient temperature, and heat sink characteristics. Concern is required even if, in addition to the usage

conditions having wide ranges, operation is within those usage conditions (for example, voltage) from the

standpoint of the problem of heat generation, and, furthermore, adjustment is required between usage

conditions such as ambient temperature, junction temperature, current, and power, which have mutual

relationships.

See section 5.2.3, Derating, in the Reliability Handbook, Revision 2.50 (R51ZZ0001EJ0250) for further

details on derating.

This application note presents temperature profiles expected for representative high-temperature

applications and derating examples that the RA4M3 Group microcontrollers can support.