Here at Moortec we develop monitors that can be used to measure the ageing process of a device in the field, by having reference structures and comparing them to live structures, we can compare the two over time.
This is one application that is being used at the moment, alongside using the information to adjust the supply to bring the chip back to the performance level that you expect, or need. This is actually quite common, particularly in devices where there is a requirement for a particular throughput.
So how does this help with choosing the lifestyle of your chip?
Ageing is complex and very dependent on use case and environment. In most modern applications neither of those is well known and often will vary over time itself.
If we take the smartphone as an example, there will be modes where it is doing very little – where the clock frequency is low, the voltage supply is low. At the other extreme it will be playing HD video – the clock will be run at high rates and the supply will be correspondingly high. Obviously if you took that device and left it in the low power state it would age at a significantly lower rate than if you left it in the high power state.
The trouble is at design time you don’t know what that ratio is. Of course this example is actually already a simplified case because more often than not there will be more than two states so you have to make assumptions about time spent in each state, and build margins in to cope with the unknowns. By allowing the system to monitor that ageing then potentially you can optimise DVFS schemes, you can predict lifetime or perhaps even reign in certain modes to insure that a particular lifetime is met.
Another example is the bitcoin mining application. This is at the other end of the scale, where devices are manufactured to sit in large arrays.
Each chip will vary with process and they will age differently partly as a result of process variation, and partly because their loads won’t always be equal. If you can monitor all those conditions, then you can optimise each of those chips to run at peak performance.
For more information about Moortec and our embedded die monitoring IP on 28nm and FinFET visit: www.moortec.com.