1 Introduction

Freescale Semiconductor produces many microcontrollers

(MCUs) specifically for the automotive market.

Automotive MCUs are designed with the following

characteristics:

• Wafer process technology from 350 nanometers (nm)

down to 90 nm

• Target many different end uses, such as powertrain

engine controllers, body controllers, chassis controllers,

safety controllers, and cluster/infotainment

• Overall MCU performance—8-bit, 16-bit, and 32-bit

• Wide range of price targets, from low cost minimal

feature set to higher cost, high performance MCUs

All of these factors have an impact on the allowable injection

currents that a device can withstand without causing any long-

term effect on the device lifetime. In general, injection current

that induces a voltage on the internal structures higher than the

operating voltage of the device can degrade the lifetime of the

transistors and other internal circuitry. However, all of these

conditions are taken into account and are covered by the

design of each MCU to ensure proper device lifetime.

1. 55 nm devices are currently in development and

qualification. A 55 nm device example will be added

to in a future version of this document.

Freescale Semiconductor

Document Number: AN4731

Application Note

Rev 1, 06/2013

Understanding Injection Current

on Freescale Automotive

Microcontrollers

by:

Randy Dees

Contents

1 Introduction................................................................1

2 Typical Internal Input/Output Circuits......................3

3 What is injection current?.........................................5

3.1 No injection current.......................................5

3.2 Externally limiting injection

current............................................................5

3.3 Injection due to overshoot.............................6

4 Considerations for analog input

injection ....................................................................7

5 Data sheet specifications for injection

current ......................................................................7

6 Example Data Sheet Excerpts and

Measurement Data.....................................................8

6.1 S12 Example..................................................8

6.2 MPC5554 example.......................................10

6.3 MPC567xF/MPC5676R

example........................................................13

6.4 MPC56xxB/C/D example............................18

7 Summary.................................................................21

A Temperature Profile.................................................21

Factors that affect the injection current capabilities of an MCU are as follows:

• Wafer process technology (transistor geometry, support for high voltage transistors)

• MCU maximum junction temperature, which implies a maximum operating temperature

• Intended market space, which may imply a more aggressive lifetime temperature profile

The following table shows the minimum transistor sizes for the different wafer process technologies and the device families

in those wafer technologies. Minimum gate sized transistors are not generally used in the input and output (I/O) circuits of

the device. Typically, the I/O circuits use larger transistors and even a thicker gate oxide to enhance the lifetime of the MCU

input and output circuitry. For example, in both the 90 nm and the 55 nm processes, the transistors used in the I/O circuit

have the same transistor gate width (0.72 micron [720 nm]) and have the same gate oxide thickness (150Å).

The following table shows the range of MCUs that are designed primarily for the automotive market.

Table 1. Example devices and wafer process technology size

Wafer process technology

(minimum transistor gate

size)

Example devices

350 nm MPC555

250 nm MPC56x, S08D, S08S, S12, S12X, S12Z

180 nm S08RN, S12, S12X, S12Z

130 nm MPC5534, MPC555x, MPC556x

90 nm MPC560xB, MPC560xC, MPC560xD, MPC560xP, MPC560xS, MPC563xM, MPC564xB,

MPC564xA, MPC564xS, MPC567xF, MPC5676R

55 nm MPC5744P, MPC5744K, MPC5746M, MPC5777M

In addition to the transistor geometry and type, the maximum junction temperature for which a device is designed has an

impact on the allowable injection current. Most automotive MCUs are designed for a maximum junction temperature (T

) of

150°C; however, some families of devices may be designed for higher (165°C) or lower (125°C, or even lower) junction

temperatures. The following table shows the typical junction temperatures for different types of automotive applications.

Table 2. Market space versus temperature ranges

Market space Typical automotive location Typical maximum junction

temperature required

Infotainment In passenger compartment 100°C

Body Outside the passenger compartment 115°C

Safety Outside or inside the passenger

compartment and outside the engine

compartment

115°C

Chassis Outside the passenger compartment, but

could be in the engine compartment,

although not mounted directly on the

engine itself

125°C

Powertrain Inside the engine compartment or in the

transmission

150°C or even 165°C

2. Under-hood Powertrain applications generally require a higher temperature profile over the life of the MCU than a

MCU intended for the passenger compartment (such as the chassis controller or infotainment modules).

Introduction

Understanding Injection Current on Freescale Automotive Microcontrollers, Rev 1, 06/2013

2 Freescale Semiconductor, Inc.