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
2
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
J
) 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 NXP Automotive Microcontrollers, Rev. 2, 12/2017
2 NXP Semiconductors