Automotive Chips are different from the regular chips used in other applications like smart phones, music systems, laptops, etc. One needs to consider the extreme environmental conditions of engine compartment, transmission or exhaust system and design the IC to work at high temperature and voltage rages.
At the chip-level, the designer would like to know what the Process variation, Voltage levels and local Temperatures (PVT) are so that they can control the chip operation, keeping it operating safely and within specifications, instead of failing from heat-induced electromigration failures or supply voltages out of spec.
Some of the automotive IC design challenges are:
- Adherence to standards like ISO 26262
- Long term commitment from suppliers
- Monitoring aging effects
- Long development cycles
Chips inside of cars can use bleeding edge 7nm all the way up to mature 180nm nodes. The smaller the node, the greater the impact of process variation has on the reliability.
Thermal effects continue to be important for automotive ICs:
- FinFET structures are less able to dissipate heat than planar CMOS
- Increased density is leading to increased thermal challenges
- Electrical OverStress (EOS)
- Electromigration (EM)
- Hot carrier aging
- Increased Negative Bias Temperature Instability (NBTI)
- Device leakage causes heat and heat causes more leakage (Thermal runaway)
- Leakage to increase when we move from one FinFET node to the next smaller node
For automobiles the environmental temperature range is typically -40C to 125C, but the junction temperature of the IC is going to be even hotter than 125C worst case based on the number of transistors, process node, operating frequency and voltage levels. Having multiple Temperature monitors on-chip is a wise choice in managing the thermal specification. As a chip reaches its thermal limits then the control logic can be used to lower voltage levels, decrease frequency or a little of both.