MSP430F5438A: POR Control Internal and External

Hi Mark,

thank you very much for asking this important question. I am happy being able to disagree with your last assumption. It is definitely possible to operate MSP430 devices safely on power up, even without an external voltage supervisor with all MSP430 devices, which have an integrated BOR. This includes all MSP430F5xxx/F6xxx, F4xx, F2xx, G2xx, CC430, and all MSP430 FRAM devices. Only with a few MSP430F1xx we have some of the oldest derivatives not having BOR on chip.

Though, as in many cases, there are some details to consider. As these details are a bit different dependent on the MSP430 device family, I'll focus here on the derivative of your interest, means MSP430F5438A.

The device's recommended operating range is specified from 1.8V to 3.6V. Dependent on the ramp up speed of the supply voltage in your application, the applied reset components, the device will startup at respective voltages. As long as operating at default settings, means e.g. in the initial state after BOR or after HW reset, the device is capable to run at voltages of the integrated BOR. The gap between BOR and 1.8V usually is passed in this state, by executing the on-chip boot code (not accessible or changeable by the user) and the reset delay. In some extreme application cases though, where the ramp up of the supply voltage is extremely slow, the MSP430 might start executing user's code, before reaching 1.8V. If this is the case, still MSP430 could operate without an external SVS, if e.g. the user's code initializes the integrated SVS to monitor the supply voltage, and start modifying peripheral and clock system settings only after having reached 1.8V or higher supply voltage levels. If the ramp up behavior of the supply voltage should be deterministic, also a delay might help here, though probably not a realistic scenario.

The additional careabouts are e.g. the handling of the Core Voltages. As e.g. visible in the datasheet, certain clocking speed requires higher core voltage levels, than the default one. In return, also the higher core voltages require a certain higher operating voltage levels than 1.8V. Thus again, similar to the previous statements, one needs to assure not switching to higher core voltage levels and/or clocking speed, before the device supply voltage has reached the specified minimum values.

Of course the same applies for the shut down scenarios. This means dependent on the clocking speed and core voltage settings, the integrated SVS has to be configured to prevent running the device outside of the specified operating range.

I hope this gives you a better insight. Of course in the device's datasheet and User's Guide you can find more details on this topic. Also please check the device's errata sheet on potential additional aspects, related to your specific use case.

Best regards

Peter

Hi Mark,

please let us know, whether your questions have been answered sufficiently, or you still need support on this. Many thanks in advance.

Best regards

Peter

Thank you Peter. No more support on this is needed.