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LS1043A maximum core temperature

Hi, My LS1043AXE7QQB (105C rated) core (thermal diode reading) is running at 65C in normal operations of 25C ambiant. We have a production test of operating the system with ambiant temperature at 70C during 16h (once for each system). During this test, the core rises to 121C. We don't experience any problem and we are going to improve the thermal management to reduce that. What is the effect of operating the cpu over 105 for a short period and what would be the acceptable maximum core temp for 16h?

Re: LS1043A maximum core temperature

Hello,

For the QorIQ Layerscape family (LS1043A, LS1046A, LX2160A — all share the same thermal rating framework):

Parameter	Value	Source
Maximum operating Tj	105°C	Datasheet
Absolute maximum / Storage Tstg	150°C (≤1008 h cumulative at 150°C)	Datasheet Table — Absolute Maximum Ratings

The 105°C Tj(max) refers to the silicon junction temperature as measured by the internal thermal diode — which is exactly what your core temperature reading reflects.

2. Effect of Operating Above 105°C

Official position from multiple support cases on the same processor family:

"Operating above Tj(max) = 105°C risks device reliability degradation and is not a supported operating condition."

"Exposing device to Absolute Maximum Ratings conditions for long periods of time may affect reliability or cause permanent damage."

"The device must not operate at temperatures > 105°C."

From a semiconductor physics standpoint, exceeding Tj(max) accelerates several well-known wearout mechanisms:

Electromigration — metal interconnect migration, accelerates ~exponentially with temperature
TDDB (Time-Dependent Dielectric Breakdown) — gate oxide degradation
NBTI (Negative Bias Temperature Instability) — threshold voltage shift in PMOS
Hot carrier injection — impacts transistor characteristics over time

All of these follow Arrhenius kinetics: degradation rate roughly doubles every ~10°C above the qualification limit. At 121°C (16°C over the rated 105°C), degradation mechanisms run at approximately 3–4× the qualified rate. This does not cause immediate/catastrophic failure — the device will function — but it consumes lifetime reliability budget at an accelerated pace.

The absence of observed failures during the test is expected: at 121°C, you are far below the 150°C storage temperature where physical damage occurs immediately. The impact is silent reliability erosion, not instant damage.

Regards