Hello,
Since the Keil toolset supports the LPC2478, I thought you might be interested in this problem report sent to NXP:
"Hello, We have an issue with a LPC2478 working at a temperature of 80 degrees and higher. The processor has almost all of its peripherals in use when inserted into the environmental chamber - running an RTX operating system, LCD, UART etc. We see a strange phenomenon: If we use Fcco 288[MHz], and a CPU clock of 72[MHZ], the processor stops working due to a data abort almost immediately after being inserted into the chamber. We tried many other combinations (keeping in mind that we must have USB active at all times, which limits our choices, of course), only to find that driving Fcco at 480[MHz] and the CPU somewhat slower that desired - at 68.57[MHz] "solves" this problem. This issue is worse on machines that have the LCD controller is use so we suspect insufficient head dissipation at 72[MHz], when the processor is loaded. Can you confirm this issue or perhaps conduct further tests?
Kind regards, Tamir Michael"
IS the device specified to work at those temperatures?
Normally, not. The product is required to operate at up to 70 degrees but the LPC2478 itself is specified to operate normally at up to 85 degrees. This issue was discovered when the client pushed the system to its limits. I feel that this really needs to be explained as some components are expected to operate for years without a critical failure - no less, under harsh conditions. I'm considering a variable PLL frequency depending on the ambient temperature - I have a I2C temperature sensor available on each PCB.
The product is supposed to operate at environment temperatures of 70 degrees. However, since it will be installed inside a metal casing, it is conceivable that the supply and other elements will boost the immediate environment of the controller to a higher temperature.