Hi guys,

I am working with CD4067B on a project. I am sending the select signals A,B,C,D and the inhibit signal using MSP430F6736A. However, I am unable to switch the input lines using the select signals. I get the output from the mux as the input it gets on line 0(pin#9) even when I change the select signals to a different number. Even if I change the inhibit signal to logic 1, the mux selects line 0 and shows me the output as the output that is on line 0.



Here is the circuit that I have connected. The inputs coming to the multiplexer are analog input lines of 0-1V range. I am using a MSP430F6736A to convert the analog output voltage line from the mux. I have connected the output line of the mux to the analog input line of the micro-controller.

Is there an error in the circuit?

Could you help me out with the issue I am facing?



Thank you,

Keval

 

If you use 12 V for VDD, the control inputs will not be 5 volt logic compatible. See the datasheet specification for input levels.

You will require some sort of level shifter to drive the control inputs. [EDIT]: It looks the the 4504 would be suitable.

 

If you use 12 V for VDD, the control inputs will not be 5 volt logic compatible. See the datasheet specification for input levels.

You will require some sort of level shifter to drive the control inputs.

I can set the VDD at 10V, which will require +3V as logic high.
How do I exactly implement a level shifter?
How does it work? Could you elaborate?

Thank you for the help.
Appreciate it.

 

No, if VDD is 10 V you will require a minimum of 7 volts for logic HIGH. 3 V is the maximum that will be treated at logic LOW.

You can use a part like the CD4504 which is a complete level shifter with totem pole outputs which will be the lowest power solution. The alternative is an open-collector or open-drain non-inverting buffer that is powered with 5 V (or whatever you are using for the processor) and will withstand 10 or 15 volts, as required, on its outputs. You would require pullup resistors, which will make for higher power consumption, but you can probably use quite high values unless you need fast switching. Resistors of perhaps 1 megohm would be functional, but because there is some capacitance associated with CMOS inputs, the high value will reduce the slew rate. Of course the old 4000 series isn't very fast to begin with.

NXP/Nexperia HEF4000 series appears to have been redesigned with more modern technology. The parts that I have looked at are all much faster than the old 4000 series while still allowing operation over the wide supply voltage range. I don't know if they make the 4067. I also don't know if the new parts are available in through-hole packages.

You should be able to find some applications notes on the web covering how to do level shifting. It is a common requirement, though with modern logic families the requirement is usually for signals ranging between a little over a volt and 5 volts, and at very high speed.

 

If you only have a 1V signal then just run the mux from the microprocessor power supply.

 

Thank you guys.
I provided a +5V power supply to the mux and it solved the issue.

Thank you so much for the quick replies.
Appreciate it.