TI Family,
This thread builds off of this one -->(+) Very slow rising Vcc and BOR - MSP low-power microcontroller forum - MSP low-power microcontrollers - TI E2E support forums
However, it adds an extra question as follows:
Assuming a user had a very slow ramp (3V/sec or LONGER) up for Vcc to reach 1.8V (again in the order of seconds) would the MSP430 maintain a reset condition until it reached or exceeded 1.8V? The answer per the DS up to <3V/sec ramp, is a resounding Yes.
However it goes a bit further where the user needs to ensure that a very slow ramp up does not cause improper operation of the control nor causes the MCU to lock-up.
Therefore, will the BOR circuit hold reset for (X # of msec) after Vcc reaches it’s threshold?
Now, realizing that any MSP430 device with BOR circuitry does what it is meant to do: Protect the part by holding it in reset in case of a brownout. The BOR circuitry, however, is not 100% fine-tuned in silicon to trigger at exactly 1.799999xxxV and therefore has some level of tolerance associated with it. This of course presents us with the question: what if I am just at that gap in spec?
To that, per the aforementioned e2e post, consider a case where the BOR releases early e.g. at 1.6V; the part is rated to work only from 1.8V onwards...In this case code execution will proceed as expected provided MCLK stays at the default DCO. This is also mentioned in a note in the DS.
BUT I’m not sure we explicitly spec the “BOR circuit hold reset for X msec after Vcc reaches its threshold” value itself?
ULTIMATELY it would be very helpful to know the Reset hold time for the BOR after Vcc reached the threshold voltage. Knowing this and the tolerance on the threshold would imply a minimum ramp time for a user to avoid operating in this no man’s land. It’s safe to say that during testing and possible during some odd “real life” operation a user could get into a condition in which the Vcc ramp could be slower than 3V/s.
Comments welcomed and appreciated!
TY,
CY