CCS/MSP430F6638: MSP430F6638 input logic level

Hi Mike,

The specs of  Schmitt trigger are the specs of digital input. Actually, the structure of a pin as digital input is a Schmitt trigger. But we only have the test data for 1.8V/3.3V DVCC.

The maximum leakage current of a pin is 50nA, so the voltage apply at the pin through a 1k pullup resistor is (3.3V - 50nA*1Kohm). According to the voltage dropout, the 1k doesn't over the maximum. But the current consumption may increase by 3.3V/1k = 3.3mA when pushing the button. You may consider this influence.

The internal pullup resistor is between 20-50kohm, you can refer to this value.

It's better to have a own decap closing to the button.

Hi Winter,

Thank you very much for your answer. So according to table 5.8 all my I/O inputs should not be higher than 2.10 V  for high logic level ? This means that if I have a 3.3 V and 0 V external logic signal this will not work because of the 2.10 V max threshold and 0.75 V min threshold ? In others words if I have a 3.3 V input ( >2.10 V) then the F6638 wouldn't be able to recognize a high level logic input ? Same, if I have a input voltage lower than 0.75 V ? If yes this is problematic, how should I deal with that ? 

Also, the datasheet talks about 1.8 and 3 V. Then what are the logic levels for 3.3 V ? 

Finally, I'm using an external pullup resistor as you have seen it in the scheme above, and not the internal one. Should the external pullup resistor be in the 20-50 kohms range ? 

Thank you.

Regards,

Mike

Hello,

The max 2.10V doesn't mean all I/O inputs should not higher than that value. It means the high logic voltage varies from 1.50V to 2.10V for different devices for 3.0V DVCC. To handle the difference between devices, you should ensure all I/O inputs higher than 2.10V for high logic level. Conversely, for low logic level, ensure all I/O inputs lower than the 0.75V, minimum value of VIT-. 

We don't have test data at 3.3V power supply.

Use external pullup resistor with value in the range of internal one is OK. 

Hi Winter,

Thank you for your response. I don't understand then why there is a range. I mean if we should ensure that all I/O inputs are higer than 2.10 V for high logic level, this means in the datasheet we should have something like 2.10 V is the minimum input voltage to get high logic level and not that 2.10 is a max value. I mean I didn't understand this 1.50 and 2.10 V range. Is this the range for the MSP430F663X family ? 

Thank you.

Regards,

Mike

Hi Winter,

Thank you for your help.

Best regards,

Mike