We recently did a parts stress analysis for a new PCB in which we are using a TMS320F28375DPTPT device. The product we are working on is a power converter, and one of our initial customers requested that we use the derating guidelines presented in Appendix A of the IPC-9592 “Performance Parameters for Power Conversion Devices” standard. For ICs, this standard presents derating guidelines for three generic categories of parts: Silicon Digital (MOS & Bipolar), Silicon Linear ICs (Bipolar), and Silicon Linear ICs (JFET & MOS). I’ve assumed that the first category is the most appropriate match for the 28375D device. One of the derating parameters is “Frequency”, and for a 10-year stress factor, they say to operate these types of devices at 90% or less of the rated maximum frequency. They later provide a brief explanation for this derating parameter as:
Maximum Operating Frequency needs to be Derated to below the specified Max Operating Frequency to allow for device performance degradation over time due to Hot Carrier Injection (HCI) and Negative Bias Transistor Instability (NBTI) effects. HCI and NBTI effects degrade MPU performance by causing Core transistor VT to drift upwards with the passage of time; (absolute value of VT for PMOS transistors). This especially affects processors and DRAMs.
We’ve been using C2000 devices for several years across many designs (280x, 281x, 2833x, 2806x, and now 2837x) and we’ve always clocked these parts at the maximum rated SYSCLK frequency. For this new design, we’re planning on running the 28375D at the maximum system clock rate of 200MHz. I’ve never come across any literature on the C2000 devices that suggests that designers should run these MCUs at lower frequencies if they want to extend their operating life in the end product. I’m assuming that when TI spec’s the maximum CPU frequency, this is already a derated number that takes into account the maximum operating temperature and some amount of operation longevity (5, 10, 20 years?) – particularly given that many of these devices are used in industrial and white goods applications where the customer expects 10+ years of operating life? Can anyone confirm this assumption - and hence confirm that we do not need to apply this 90% Frequency derating guideline to the 28375D device?
