MSP430F6736: MSP430F6736 AUX Issue

Hello Hank,

I am sorry, but your description is not sufficient. What do you mean by stating AUX1 and AUX2 are used for voltage detection? The auxiliary supplies are not intended to be used for voltage detection, but should be used as alternative supplies for the MSP430, in case the primary supply fails. Could you please give us more details on the setup you've implemented? Many thanks in advance.

Best regards

Peter

Hello Peter

here the part of the sch,we using aux2 as the detect funtion by AUX2  flag,if the aux2 is lower  than 2.4V,the flag is on. by this way ,the mcu judge the power supply is on or off.

while the mcu voltage  is 3.3V and aux2 flage is  setted 2.4v  ,but the aux2 voltage is 3.6v or 3.7v while the power supply is given.

Does the mcu will working  wrong state?. what about the max voltage of the aux can bear?,the SPEC. have pointed is 3.6V max.

and the aux2 is higher than the ohter power pin.  the MCU seems working on right ,what's the risk it may happen?

Hello Hank,

if I understood your setup and the intentions on your side, I can make the following statements.

The intention of the auxiliary voltages is a different one to what you're trying to use it for. AUX1 and AUX2 are auxiliary supplies. The intended use case is to use these power supply connections in case the primary DVCC supply drops below a certain value. Like e.g. on mains power fail switching from the mains supply to a backup battery or capacitor.

This in return means, the MSP430 is not using these auxiliary supplies as long as DVCC is in the expected range. There is only a circuitry checking these power supplies, to make sure, whether the system can switch in case of need to the auxiliary power supply. This again means, the power consumption on the auxiliary pins in supply mode through DVCC is extremely low. This is probably the reason, why the voltage you're measuring at AUX2 is high, and maybe even higher than the primary supply voltage.

As specified in the datasheet, the voltage at the auxiliary supply pins should not exceed the limit of 3.6V. Please keep also in mind the recommended capacitances at the auxiliary supply pins.

Best regards

Peter