SLAA666A March 2015 – January 2020 MSP430F6720 , MSP430F6720A , MSP430F6721 , MSP430F6721A , MSP430F6723 , MSP430F6723A , MSP430F6724 , MSP430F6724A , MSP430F6725 , MSP430F6725A , MSP430F6726 , MSP430F6726A , MSP430F6730 , MSP430F6730A , MSP430F6731 , MSP430F6731A , MSP430F6733 , MSP430F6733A , MSP430F6734 , MSP430F6734A , MSP430F6735 , MSP430F6735A , MSP430F6736 , MSP430F6736A , MSP430F6745 , MSP430F67451 , MSP430F67451A , MSP430F6745A , MSP430F6746 , MSP430F67461 , MSP430F67461A , MSP430F6746A , MSP430F6747 , MSP430F67471 , MSP430F67471A , MSP430F6747A , MSP430F6748 , MSP430F67481 , MSP430F67481A , MSP430F6748A , MSP430F6749 , MSP430F67491 , MSP430F67491A , MSP430F6749A , MSP430F6765 , MSP430F67651 , MSP430F67651A , MSP430F6765A , MSP430F6766 , MSP430F67661 , MSP430F67661A , MSP430F6766A , MSP430F6767 , MSP430F67671 , MSP430F67671A , MSP430F6767A , MSP430F6768 , MSP430F67681 , MSP430F67681A , MSP430F6768A , MSP430F6769 , MSP430F67691 , MSP430F67691A , MSP430F6769A , MSP430F6775 , MSP430F67751 , MSP430F67751A , MSP430F6775A , MSP430F6776 , MSP430F67761 , MSP430F67761A , MSP430F6776A , MSP430F6777 , MSP430F67771 , MSP430F67771A , MSP430F6777A , MSP430F6778 , MSP430F67781 , MSP430F67781A , MSP430F6778A , MSP430F6779 , MSP430F67791 , MSP430F67791A , MSP430F6779A
This application report describes the enhancements of the MSP430F67xxA devices from the non-A MSP430F67xx devices. In the course of this application report, the MSP430F67xx errata that are fixed in the MSP430F67xxA and the additional features added to the MSP430F67xxA devices are discussed. In addition, metrology results are compared to further show that the changes implemented in the MSP430F67xxA devices do not affect the metrology performance.
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The MSP430F67xxA devices are the latest e-meter SoCs from Texas Instruments for 1-phase and 3-phase meters. These devices offer enhancements from the previous non-A MSP430F67xx e-meter SoCs while still maintaining all of the features of the non-A chips so that a non-A device can be replaced with the corresponding A version of that chip. As an example, this would allow a MSP430F6736-based design to be upgraded by swapping its MSP430F6736 with a MSP430F6736A. This can be done for all of the F67xxA chips, which are all mentioned below:
Note that the "A" in the MSP430F67xxA devices is listed on a chip as a part of the part number and is independent of the letter listed as the silicon revision number. For example, a non-A device may be labeled on the chip as being "Rev A" but is still considered a non-A device. Similarly, a MSP430F67xxA device may say "Rev B" but is still a MSP430F67xxA chip. Care must be taken not to confuse the revision letter on the chip with being a part of the chip part number.
Also, when comparing the MSP430F67xx non-A devices to the MSP430F67xxA devices, the following changes were made onto the MSP430F67xxA:
One erratum in the non-A MSP430F67xx devices was the AUXPMM1 errata that is listed in the device erratasheets. This erratum covers the AUX module, which is a module that allows switching the supply that powers the chip from DVCC/AVCC to AUXVCC1 or AUXVCC2 if DVCC/AVCC falls below a certain voltage threshold. After DVCC/AVCC rises above the associated threshold, the chip should automatically switch back to being powered by DVCC/AVCC. However, in this erratum, there could be a case where the AUX module would not switch back to DVCC when it is running from AUXVCC1 or AUXVCC2. In particular, when the system is running with the AUXVCC1/AUXVCC2 supply after DVCC/AVCC is lost, and if the AUXVCC1 voltage goes lower than the SVSH setting for POR but above the BORH level, the system cannot switch back to DVCC after DVCC ramps back up again. In a typical application, DVCC/AVCC is powered from mains through a power supply, while AUXVCC1 or AUXVCC2 are connected to batteries. As a result of this configuration and this erratum, the chip would continue to be powered from the battery despite Mains being present. This would eventually lead to the battery being depleted. In the MSP430F67xxA devices, this erratum has been fixed, which prevents this sequence of events from happening.
Another erratum fixed in the MSP430F67xxA devices was the RTC8 erratum mentioned in device erratasheets. This particular erratum is most pertinent to the high-accuracy poly-phase metering SoCs, because they have the RTCCAP functionality present. For this RTCCAP feature, whenever there is an event (a rising or falling edge) detected on any of the RTCCAP pins, the RTC time when this occurs is logged. In a typical application, the RTCCAP pins could be connected to a meter case so that whenever someone tries to open the case, a switch would trip and send a rising or falling edge signal to the RTCCAP pin. From there, the time of this case tamper event could be logged.
In the F67xx devices, the backup subsystem that includes the RTC is powered independently by AUXVCC3 (instead of by DVCC/AVCC, AUXVCC1, or AUXVCC2). Because the rest of the chip does not need to be powered, this reduces the current draw when only the RTC needs to be functional. However, due to the RTC8 erratum, the tamper detection function triggered by the RTCCAP0 and RTCCAP1 pins cannot get a correct time stamp value when DVCC and AUXVCC1 are off. To ensure that the correct time stamp is obtained, DVCC and AUXVCC1 should not be off. As a result, the current draw is increased when this feature is necessary. For the MSP430F67xxA devices, this erratum is fixed so that the correct time stamp can be captured with only voltage at AUXVCC3 present, thereby preventing the increase in current from having to power the rest of the chip via DVCC/AVCC, AUXVCC1, or AUXVCC2.