74LCX541/SO

[Rushali]

Hello Everyone,

I am facing problem in ADC section of  our project schematic. We are using ADS8505 Analog to digital converter as the output of ADC ranges from 0v to 5V and microcontroller which we are using(STM32F413ZGT6) is connected to 3.3 Volts supply voltage we had to incorporate a Low voltage CMOS buffer in between i.e. (74LCX541/SO).

There aren't enough test circuit example available on internet for (74LCX541/SO).Please suggest how can we incorporate (74LCX541/SO) with STM32F413ZGT6 microcontroller.

Also attaching existing schematic for your reference.

[Peter BENSCH · Accepted solution]

You do not need a receive buffer like the 74LCX541 because many pins on the STM32F413, in your case the entire port B, are 5V-tolerant. You should just be careful not to activate the pull-ups or pull-downs of the port's GPIOs.

Hope that helps?

Regards
/Peter

[Rushali]

 Hii Peter BENSCH,

Thank you for suggesting the above changes will surely implement the same in future.

But in case if we want to incorporate the same using 74LCX541 how can we modify the design? Do we need to add any resistor on the individual input pins and output pins of 74LCX541.

Thank you for your kind co-operation.

[Peter BENSCH]

Well, if you already want to insert additional resistors, you are ready to change the layout. Then why not simply connect each Ax to Yx and remove U38/U39 as well as C151/C152?

Otherwise you don't need any resistors if the STM32 and U38/U39 are connected to the same 3.3V.

Apropos U38/U39: their pins 1 and 19 are correctly wired (GND = active), but incorrectly labelled: they should be called /G1 and /G2.

Regards
/Peter

[Rushali]

Dear Peter BENSCH,

Thank you for your suggestion. Will implement the same,