MCU + Analog Series: Sleep deeper and save more power with nanotimers from Texas Instruments


This guest blog post was contributed by Tariq Chang, Product Marketing Engineer responsible for sensor analog front-ends and nanotimers at Texas Instruments.

TI's ultra-low-power MSP430 FRAM microcontrollers (MCUs) are the ultimate choice for designing a system which runs off a battery or other limited power source.  By limiting current draw in low-power modes (LPMs), our MCUs significantly reduce the system’s total power consumption and increase the lifetime of the application!

What if I told you that you can even further reduce this current consumption?

Well, if your system requires long delay periods between wake up and you still are not able to meet the necessary power requirements, then the new nanotimers from Texas Instruments can help you resolve this issue.  Some applications include tamper detection and home or building automation.

These low-power wake-up timers allow the MSP430 microcontroller, like the new MSP430FR5969, to enter its lowest LPM.  In this mode, the controller’s clocking is disabled and can only be awoken through an interrupt which is sent from an external source like a nanotimer.  The TPL5x00 nanotimer family only consumes 30nA of current while in operation.  This can save up to 60-80% total system power.  In addition, the TPL51x0 has the option to power cycle the entire system by driving an external MOSFET to even further power savings!

In the picture below, you can see a conceptual diagram of how the TPL5xx0 nanotimers would affect current consumption:

It is fairly simple! The nanotimer places the system in its active operational mode every programmable delay period (which can range from 1sec to 1024secs) to perform the necessary actions and then enter back into deep sleep mode that it was once in.  You can accumulate this power savings over time and ultimately see a significant extension in lifetime or you can replace the existing batteries with ones that are smaller and lower priced!


Below we have simulated how much power savings we can achieve with a BR2325 coin cell battery.  When a one second wake up pulse is used, we can see that we achieve an additional 2 years of operational lifetime.

                

Now you are probably wondering why the MSP430 MCU does not already have this nanotimer integrated into the system so that it can achieve such low power. Well, MSP430 microcontrollers use a real-time clock (RTC) for higher accuracy and even a calendar feature on some devices.  The nanotimer uses an RC oscillator to perform the clocking function.  This RC oscillator can achieve 1% accuracy which fits most applications that are in sleep mode for most of its lifetime and only need to be woken up to take a simple measurement and possibly send information wirelessly (i.e. sensing applications).

These devices are already released and available to pair with your MSP430 microcontroller today!   

Want to know more about TI Analog? Read more posts in the series: